#### Sample records for ray measurements conducted

1. Thermal conductivity measurements of CH and Be by refraction-enhanced x-ray radiography

Ping, Yuan; King, Jim; Landen, Otto; Whitley, Heather; London, Rich; Hamel, Sebastien; Sterne, Phil; Panella, Amalia; Freeman, Rick; Collins, Gilbert

2015-06-01

Transport properties of warm dense matter are important for modeling the growth of hydrodynamic instabilities near the fuel-ablator interface in an ICF capsule, which determines the mix level in the fuel and thus is critical for successful ignition. A novel technique, time-resolved refraction-enhanced x-ray radiography, has been developed to study thermal conductivity at an interface. Experiments using OMEGA laser have been carried out for CH/Be targets isochorically heated by x-rays to measure the evolution of the density gradient at the interface due to thermal conduction. The sensitivity of this radiographic technique to discontinuities enabled observation of shock/rarefraction waves propagating away from the interface. The radiographs provide enough constraints on the temperatures, densities and scale lengths in CH and Be, respectively. Preliminary data analysis suggests that the thermal conductivities of CH and Be at near solid density and a few eV temperature are higher than predictions by the commonly used Lee-More model. Detailed analysis and comparison with various models will be presented. The work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Security, LLC, Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

2. Design of a humidity controlled sample stage for simultaneous conductivity and synchrotron X-ray scattering measurements

Jackson, Andrew; Beers, Keith M.; Chen, X. Chelsea; Hexemer, Alexander; Pople, John A.; Kerr, John B.; Balsara, Nitash P.

2013-07-01

We report on the design and operation of a novel sample stage, used to simultaneously measure X-ray scattering profiles and conductivity of a polymer electrolyte membrane (PEM) surrounded by humid air as a function of temperature and relative humidity. We present data obtained at the Advanced Light Source and Stanford Synchrotron Radiation Laboratory. We demonstrate precise humidity control and accurate determination of morphology and conductivity over a wide range of temperatures. The sample stage is used to study structure-property relationships of a semi-crystalline block copolymer PEM, sulfonated polystyrene-block-polyethylene.

3. Results from single shot grazing incidence hard x-ray damage measurements conducted at the SACLA FEL

Aquila, Andrew; Ozkan, Cigdem; Sobierajski, Ryszard; Hájková, Vera; Burian, Tomás.; Chalupsky, Jakub; Juha, Libor; Störmer, Michael; Ohashi, Haruhiko; Koyama, Takahisa; Tono, Kensuke; Inubushi, Yuichi; Yabashi, Makina; Sinn, Harald; Tschentscher, Thomas; Mancuso, Adrian P.; Gaudin, Jérôme

2013-05-01

With the development of hard X-ray free electron lasers, there is a pressing need to experimentally determine the single shot damage limits of presently used and potential future optical coating materials. To this end we present damage results, and analysis of fluence threshold limits, from grazing incidence geometry experiments conducted at the Spring-8 Angstrom Compact free electron LAser (SACLA) on Carbon coatings at 7 and 12 keV photon energies.

4. Measuring Salinity by Conductivity.

ERIC Educational Resources Information Center

Lapworth, C. J.

1981-01-01

Outlines procedures for constructing an instrument which uses an electrode and calibration methods to measure the salinity of waters in environments close to and affected by a saline estuary. (Author/DC)

5. Hydraulic Conductivity Measurements Barrow 2014

DOE Data Explorer

Katie McKnight; Tim Kneafsey; Craig Ulrich; Jil Geller

2015-02-22

Six individual ice cores were collected from Barrow Environmental Observatory in Barrow, Alaska, in May of 2013 as part of the Next Generation Ecosystem Experiment (NGEE). Each core was drilled from a different location at varying depths. A few days after drilling, the cores were stored in coolers packed with dry ice and flown to Lawrence Berkeley National Laboratory (LBNL) in Berkeley, CA. 3-dimensional images of the cores were constructed using a medical X-ray computed tomography (CT) scanner at 120kV. Hydraulic conductivity samples were extracted from these cores at LBNL Richmond Field Station in Richmond, CA, in February 2014 by cutting 5 to 8 inch segments using a chop saw. Samples were packed individually and stored at freezing temperatures to minimize any changes in structure or loss of ice content prior to analysis. Hydraulic conductivity was determined through falling head tests using a permeameter [ELE International, Model #: K-770B]. After approximately 12 hours of thaw, initial falling head tests were performed. Two to four measurements were collected on each sample and collection stopped when the applied head load exceeded 25% change from the original load. Analyses were performed between 2 to 3 times for each sample. The final hydraulic conductivity calculations were computed using methodology of Das et al., 1985.

6. Study of pressure induced polyamorphic transition in Ce-based ternary BMG using in situ x-ray scattering and electrical conductivity measurement

Chen, J.; Ma, C.; Tang, R.; Li, L.; Liu, H.; Gao, C.; Yang, W.

2015-12-01

In situ high energy x-ray scattering and electrical conductivity measurements on Ce70Al10Cu20 bulk metallic glass have been conducted using a diamond anvil cell (DAC) in conjunction with synchrotron x-rays or a laboratory electrical measurement system. The relative volumetric change (V/V0) as a function of pressure is inferred using the first sharp diffraction peak (FSDP) and the universal fractional noncubic power law[1]. The result indicates a pressure-induced polyamorphic transition at about 4 GPa in the ternary system. While the observed pressure of such polyamorphic transition in the Ce-base binary BMG is not very sensitive to its composition based on some of the previous studies[2, 3], this study indicates that such transition pressure increases considerably when a new component is added to the system. In the electrical conductivity measurement, a significant resistance change was observed in the pressure range coupled to polyamorphic transition. More discussions will be given regarding the electrical conductivity behavior of this system under high pressure to illustrate the delocalization of 4f electrons as the origin of the observed polyamorphic transition. References: 1. Zeng Q, Kono Y, Lin Y, Zeng Z, Wang J, Sinogeikin SV, Park C, Meng Y, Yang W, Mao H-K (2014) Universal fractional noncubic power law for density of metallic glasses. Physical Review Letters 112: 185502-185502 2. Zeng Q-S, Ding Y, Mao WL, Yang W, Sinogeikin SV, Shu J, Mao H-K, Jiang JZ (2010) Origin of pressure-induced polyamorphism in Ce75Al25 metallic glass. Physical Review Letters 104: 105702-105702 3. Sheng HW, Liu HZ, Cheng YQ, Wen J, Lee PL, Luo WK, Shastri SD, Ma E (2007) Polyamorphism in a metallic glass. Nature Materials DOI: 10.1038/nmat1839.

7. Thermal conductivity Measurements of Kaolite

SciTech Connect

Wang, H

2003-02-21

Testing was performed to determine the thermal conductivity of Kaolite 1600, which primarily consists of Portland cement and vermiculite. The material was made by Thermal Ceramics for refractory applications. Its combination of light weight, low density, low cost, and noncombustibility made it an attractive alternative to the materials currently used in ES-2 container for radioactive materials. Mechanical properties and energy absorption tests of the Kaolite have been conducted at the Y-12 complex. Heat transfer is also an important factor for the application of the material. The Kaolite samples are porous and trap moisture after extended storage. Thermal conductivity changes as a function of moisture content below 100 C. Thermal conductivity of the Kaolite at high temperatures (up to 700 C) are not available in the literature. There are no standard thermal conductivity values for Kaolite because each sample is somewhat different. Therefore, it is necessary to measure thermal conductivity of each type of Kaolite. Thermal conductivity measurements will help the modeling and calculation of temperatures of the ES-2 containers. This report focuses on the thermal conductivity testing effort at ORNL.

8. Temperature correction in conductivity measurements

USGS Publications Warehouse

Smith, Stanford H.

1962-01-01

Electrical conductivity has been widely used in freshwater research but usual methods employed by limnologists for converting measurements to conductance at a given temperature have not given uniformly accurate results. The temperature coefficient used to adjust conductivity of natural waters to a given temperature varies depending on the kinds and concentrations of electrolytes, the temperature at the time of measurement, and the temperature to which measurements are being adjusted. The temperature coefficient was found to differ for various lake and stream waters, and showed seasonal changes. High precision can be obtained only by determining temperature coefficients for each water studied. Mean temperature coefficients are given for various temperature ranges that may be used where less precision is required.

9. How to Measure Thermal Conductivity

Ventura, Guglielmo; Perfetti, Mauro

The methods to measure the thermal conductivity at low temperature are described: the steady-state techniques, (Sect. 2.2 ); the 3ω technique (Sect. 2.3 ); and the thermal diffusivity measurement (Sect. 2.4 ). Each of these techniques has its own advantages as well as its inherent limitations, with some techniques more appropriate to specific sample geometry, such as the 3ω technique for thin films which is discussed in detail in Sect. 2.4.2 . The radial flux method is reported in Sect. 2.2.4 , the laser flash diffusivity method in Sect. 2.4.1 and the "pulsed power or Maldonado technique" in Sect. 2.3.2 .

10. Calibration-free electrical conductivity measurements for highly conductive slags

SciTech Connect

MACDONALD,CHRISTOPHER J.; GAO,HUANG; PAL,UDAY B.; VAN DEN AVYLE,JAMES A.; MELGAARD,DAVID K.

2000-05-01

This research involves the measurement of the electrical conductivity (K) for the ESR (electroslag remelting) slag (60 wt.% CaF{sub 2} - 20 wt.% CaO - 20 wt.% Al{sub 2}O{sub 3}) used in the decontamination of radioactive stainless steel. The electrical conductivity is measured with an improved high-accuracy-height-differential technique that requires no calibration. This method consists of making continuous AC impedance measurements over several successive depth increments of the coaxial cylindrical electrodes in the ESR slag. The electrical conductivity is then calculated from the slope of the plot of inverse impedance versus the depth of the electrodes in the slag. The improvements on the existing technique include an increased electrochemical cell geometry and the capability of measuring high precision depth increments and the associated impedances. These improvements allow this technique to be used for measuring the electrical conductivity of highly conductive slags such as the ESR slag. The volatilization rate and the volatile species of the ESR slag measured through thermogravimetric (TG) and mass spectroscopy analysis, respectively, reveal that the ESR slag composition essentially remains the same throughout the electrical conductivity experiments.

11. Temperature dependence of conductivity measurement for conducting polymer

Gutierrez, Leandro; Duran, Jesus; Isah, Anne; Albers, Patrick; McDougall, Michael; Wang, Weining

2014-03-01

Conducting polymer-based solar cells are the newest generation solar cells. While research on this area has been progressing, the efficiency is still low because certain important parameters of the solar cell are still not well understood. It is of interest to study the temperature dependence of the solar cell parameters, such as conductivity of the polymer, open circuit voltage, and reverse saturation current to gain a better understanding on the solar cells. In this work, we report our temperature dependence of conductivity measurement using our in-house temperature-varying apparatus. In this project, we designed and built a temperature varying apparatus using a thermoelectric cooler module which gives enough temperature range as we need and costs much less than a cryostat. The set-up of the apparatus will be discussed. Temperature dependence of conductivity measurements for PEDOT:PSS films with different room-temperature conductivity will be compared and discussed. NJSGC-NASA Fellowship grant

12. Iterative Precise Conductivity Measurement with IDEs

PubMed Central

Hubálek, Jaromír

2015-01-01

The paper presents a new approach in the field of precise electrolytic conductivity measurements with planar thin- and thick-film electrodes. This novel measuring method was developed for measurement with comb-like electrodes called interdigitated electrodes (IDEs). Correction characteristics over a wide range of specific conductivities were determined from an interface impedance characterization of the thick-film IDEs. The local maximum of the capacitive part of the interface impedance is used for corrections to get linear responses. The measuring frequency was determined at a wide range of measured conductivity. An iteration mode of measurements was suggested to precisely measure the conductivity at the right frequency in order to achieve a highly accurate response. The method takes precise conductivity measurements in concentration ranges from 10−6 to 1 M without electrode cell replacement. PMID:26007745

13. Skin Conductance Measurement in Communication Research.

ERIC Educational Resources Information Center

Goodman, R. Irwin

1985-01-01

Describes skin conductance measurement as a physiological procedure to obtain information on onset, duration, intensity, and completion of private physiological responses to parts of films or media products. The mechanics of the technique, how measurements are recorded and analyzed, and types of skin conductance research literature are discussed.…

14. X-ray Timing Measurements

NASA Technical Reports Server (NTRS)

Strohmayer, T.

2008-01-01

We present new, extended X-ray timing measurements of the ultra-compact binary candidates V407 Vul and RX J0806.3+1527 (J0806), as well as a summary of the first high resolution X-ray spectra of 50806 obtained with the Chandra/LETG. The temporal baseline for both objects is approximately 12 years, and our measurements confirm the secular spin-up in their X-ray periods. The spin-up rate in 50806 is remarkably uniform at 3.55x10(exp -16)Hz/s, with a measurement precision of 0.2%. We place a limit (90% confidence) on 1 d dot nu < 4x10(exp -26)Hz/sq s. Interestingly, for V407 Vul we find the first evidence that the spin-up rate is slowing, with d dot\

15. Thunderstorm related variations in stratospheric conductivity measurements

NASA Technical Reports Server (NTRS)

Hu, Hua; Holzworth, Robert H.; Li, Ya QI

1989-01-01

The vector electric field and polar conductivities were measured by zero-pressure balloon-borne payloads launched from Wallops Island, Virgina during the summers of 1987 and 1988. Data were collected over thunderstorms (or electrified clouds) during 6-hour flights at altitudes near 30 km. The vector electric field measurements were made with the double Langmuir probe high-impedance method, and the direct conductivity measurements were obtained with the relaxation technique. Evidence is presented for conductivity variations over thunderstorms (or electrified clouds). It is found that both positive and negative polar conductivity data do show variations of up to a factor of 2 from ambient values associated with the disturbed periods. Some ideas for possible physical mechanisms which may be responsible for the conductivity variations over thunderstorms are also discussed in this paper.

16. An effective thermal conductivity measurement system

Madrid, F.; Jordà, X.; Vellvehi, M.; Guraya, C.; Coleto, J.; Rebollo, J.

2004-11-01

In the technical literature, there is a lack of reliable thermal parameters and, often, it is necessary to do in situ measurements for every particular material. An effective thermal conductivity measurement system has been designed and implemented to provide reliable and accurate values for that thermal parameter. The thermal conductivity of a given material is deduced from thermal resistance differential measurements of two samples. All parts of the implemented system as well as practical and theoretical solutions are described, including a power controller circuit exclusively conceived for this application. Experimental considerations to reduce the measurement error are exposed, as well as some results obtained for three different materials.

17. Thermal conductivity measurements of Summit polycrystalline silicon.

SciTech Connect

Clemens, Rebecca; Kuppers, Jaron D.; Phinney, Leslie Mary

2006-11-01

A capability for measuring the thermal conductivity of microelectromechanical systems (MEMS) materials using a steady state resistance technique was developed and used to measure the thermal conductivities of SUMMiT{trademark} V layers. Thermal conductivities were measured over two temperature ranges: 100K to 350K and 293K to 575K in order to generate two data sets. The steady state resistance technique uses surface micromachined bridge structures fabricated using the standard SUMMiT fabrication process. Electrical resistance and resistivity data are reported for poly1-poly2 laminate, poly2, poly3, and poly4 polysilicon structural layers in the SUMMiT process from 83K to 575K. Thermal conductivity measurements for these polysilicon layers demonstrate for the first time that the thermal conductivity is a function of the particular SUMMiT layer. Also, the poly2 layer has a different variation in thermal conductivity as the temperature is decreased than the poly1-poly2 laminate, poly3, and poly4 layers. As the temperature increases above room temperature, the difference in thermal conductivity between the layers decreases.

18. Conductance measurement circuit with wide dynamic range

NASA Technical Reports Server (NTRS)

Mount, Bruce E. (Inventor); Von Esch, Myron (Inventor)

1994-01-01

A conductance measurement circuit to measure conductance of a solution under test with an output voltage proportional to conductance over a 5-decade range, i.e., 0.01 uS to 1000 uS or from 0.1 uS to 10,000 uS. An increase in conductance indicates growth, or multiplication, of the bacteria in the test solution. Two circuits are used each for an alternate half-cycle time periods of an alternate squarewave in order to cause alternate and opposite currents to be applied to the test solution. The output of one of the two circuits may be scaled for a different range optimum switching frequency dependent upon the solution conductance and to enable uninterrupted measurement over the complete 5-decade range. This circuitry provides two overlapping ranges of conductance which can be read simultaneously without discontinuity thereby eliminating range switching within the basic circuitry. A VCO is used to automatically change the operating frequency according to the particular value of the conductance being measured, and comparators indicate which range is valid and also facilitate computer-controlled data acquisition. A multiplexer may be used to monitor any number of solutions under test continuously.

19. Local measurement of thermal conductivity and diffusivity

SciTech Connect

Hurley, David H.; Schley, Robert S.; Khafizov, Marat; Wendt, Brycen L.

2015-12-01

Simultaneous measurement of local thermal diffusivity and conductivity is demonstrated on a range of ceramic samples. This was accomplished by measuring the temperature field spatial profile of samples excited by an amplitude modulated continuous wave laser beam. A thin gold film is applied to the samples to ensure strong optical absorption and to establish a second boundary condition that introduces an expression containing the substrate thermal conductivity. The diffusivity and conductivity are obtained by comparing the measured phase profile of the temperature field to a continuum based model. A sensitivity analysis is used to identify the optimal film thickness for extracting the both substrate conductivity and diffusivity. Proof of principle studies were conducted on a range of samples having thermal properties that are representative of current and advanced accident tolerant nuclear fuels. It is shown that by including the Kapitza resistance as an additional fitting parameter, the measured conductivity and diffusivity of all the samples considered agree closely with literature values. Lastly, a distinguishing feature of this technique is that it does not require a priori knowledge of the optical spot size which greatly increases measurement reliability and reproducibility.

20. Local measurement of thermal conductivity and diffusivity.

PubMed

Hurley, David H; Schley, Robert S; Khafizov, Marat; Wendt, Brycen L

2015-12-01

Simultaneous measurement of local thermal diffusivity and conductivity is demonstrated on a range of ceramic samples. This was accomplished by measuring the temperature field spatial profile of samples excited by an amplitude modulated continuous wave laser beam. A thin gold film is applied to the samples to ensure strong optical absorption and to establish a second boundary condition that introduces an expression containing the substrate thermal conductivity. The diffusivity and conductivity are obtained by comparing the measured phase profile of the temperature field to a continuum based model. A sensitivity analysis is used to identify the optimal film thickness for extracting the both substrate conductivity and diffusivity. Proof of principle studies were conducted on a range of samples having thermal properties that are representatives of current and advanced accident tolerant nuclear fuels. It is shown that by including the Kapitza resistance as an additional fitting parameter, the measured conductivity and diffusivity of all the samples considered agreed closely with the literature values. A distinguishing feature of this technique is that it does not require a priori knowledge of the optical spot size which greatly increases measurement reliability and reproducibility. PMID:26724041

1. Local measurement of thermal conductivity and diffusivity

Hurley, David H.; Schley, Robert S.; Khafizov, Marat; Wendt, Brycen L.

2015-12-01

Simultaneous measurement of local thermal diffusivity and conductivity is demonstrated on a range of ceramic samples. This was accomplished by measuring the temperature field spatial profile of samples excited by an amplitude modulated continuous wave laser beam. A thin gold film is applied to the samples to ensure strong optical absorption and to establish a second boundary condition that introduces an expression containing the substrate thermal conductivity. The diffusivity and conductivity are obtained by comparing the measured phase profile of the temperature field to a continuum based model. A sensitivity analysis is used to identify the optimal film thickness for extracting the both substrate conductivity and diffusivity. Proof of principle studies were conducted on a range of samples having thermal properties that are representatives of current and advanced accident tolerant nuclear fuels. It is shown that by including the Kapitza resistance as an additional fitting parameter, the measured conductivity and diffusivity of all the samples considered agreed closely with the literature values. A distinguishing feature of this technique is that it does not require a priori knowledge of the optical spot size which greatly increases measurement reliability and reproducibility.

2. Local measurement of thermal conductivity and diffusivity

SciTech Connect

Hurley, David H.; Schley, Robert S.; Khafizov, Marat; Wendt, Brycen L.

2015-12-15

Simultaneous measurement of local thermal diffusivity and conductivity is demonstrated on a range of ceramic samples. This was accomplished by measuring the temperature field spatial profile of samples excited by an amplitude modulated continuous wave laser beam. A thin gold film is applied to the samples to ensure strong optical absorption and to establish a second boundary condition that introduces an expression containing the substrate thermal conductivity. The diffusivity and conductivity are obtained by comparing the measured phase profile of the temperature field to a continuum based model. A sensitivity analysis is used to identify the optimal film thickness for extracting the both substrate conductivity and diffusivity. Proof of principle studies were conducted on a range of samples having thermal properties that are representatives of current and advanced accident tolerant nuclear fuels. It is shown that by including the Kapitza resistance as an additional fitting parameter, the measured conductivity and diffusivity of all the samples considered agreed closely with the literature values. A distinguishing feature of this technique is that it does not require a priori knowledge of the optical spot size which greatly increases measurement reliability and reproducibility.

3. Local measurement of thermal conductivity and diffusivity

DOE PAGESBeta

Hurley, David H.; Schley, Robert S.; Khafizov, Marat; Wendt, Brycen L.

2015-12-01

Simultaneous measurement of local thermal diffusivity and conductivity is demonstrated on a range of ceramic samples. This was accomplished by measuring the temperature field spatial profile of samples excited by an amplitude modulated continuous wave laser beam. A thin gold film is applied to the samples to ensure strong optical absorption and to establish a second boundary condition that introduces an expression containing the substrate thermal conductivity. The diffusivity and conductivity are obtained by comparing the measured phase profile of the temperature field to a continuum based model. A sensitivity analysis is used to identify the optimal film thickness formore » extracting the both substrate conductivity and diffusivity. Proof of principle studies were conducted on a range of samples having thermal properties that are representative of current and advanced accident tolerant nuclear fuels. It is shown that by including the Kapitza resistance as an additional fitting parameter, the measured conductivity and diffusivity of all the samples considered agree closely with literature values. Lastly, a distinguishing feature of this technique is that it does not require a priori knowledge of the optical spot size which greatly increases measurement reliability and reproducibility.« less

4. Inductive Measurement of Plasma Jet Electrical Conductivity

NASA Technical Reports Server (NTRS)

Turner, Matthew W.; Hawk, Clark W.; Litchford, Ron J.

2005-01-01

An inductive probing scheme, originally developed for shock tube studies, has been adapted to measure explosive plasma jet conductivities. In this method, the perturbation of an applied magnetic field by a plasma jet induces a voltage in a search coil, which, in turn, can be used to infer electrical conductivity through the inversion of a Fredholm integral equation of the first kind. A 1-inch diameter probe was designed and constructed, and calibration was accomplished by firing an aluminum slug through the probe using a light-gas gun. Exploratory laboratory experiments were carried out using plasma jets expelled from 15-gram high explosive shaped charges. Measured conductivities were in the range of 3 kS/m for unseeded octol charges and 20 kS/m for seeded octol charges containing 2% potassium carbonate by mass.

5. Flow rate measurement in aggressive conductive fluids

Dubovikova, Nataliia; Kolesnikov, Yuri; Karcher, Christian

2014-03-01

Two non-contact experimental methods of flow rate measurements for aggressive conductive liquids are described. The techniques are based on electromagnetic forces and Faraday's law: Lorentz force is induced inside moving conductive liquid under influence of variable magnetic field of permanent magnets. They are mounted along a liquid metal channel or (in case of the second method) inserted into rotated metal wheels. The force acts in the opposite of fluids' velocity direction and hence it is possible to measure reaction force of it that takes place according to Newton's law on magnetic field source - permanent magnets. And by knowing the force, which linearly depends on velocity, one can calculate mean flow rate of liquid. In addition experimental "dry" calibration and its results are described for one of the measurements' techniques.

6. Martian Surface after Phoenix's Conductivity Measurements

NASA Technical Reports Server (NTRS)

2008-01-01

NASA's Phoenix Mars Lander's Robotic Arm Camera took this image on Sol 71 (August 6, 2008), the 71st Martian day after landing. The shadow shows the outline of Phoenix's Thermal and Electrical Conductivity Probe, or TECP. The holes seen in the Martian surface were made by this instrument to measure the soil's conductivity. A fork-like probe inserted into the soil checks how well heat and electricity move through the soil from one prong to another.

The measurements completed Wednesday ran from the afternoon of Phoenix's 70th Martian day, or sol, to the morning of Sol 71.

The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

7. Measuring Contact Thermal Conductances at Low Temperatures

NASA Technical Reports Server (NTRS)

Salerno, Louis J.; Kittel, Peter; Brooks, Walter; Spivak, Alan L.; Marks, William G., Jr.

1987-01-01

Instrument measures thermal conductance of pressed contacts in liquid helium. Makes measurements automatically as function of force on pairs of brass samples having various surface finishes. Developed as part of effort to determine heat-transfer characteristics of bolted joints on cryogenically cooled focal planes in infrared equipment. Cylindrical chamber hangs from cover plate in bath of liquid helium. Inside chamber rocker arm applies controlled force to samples. Upper sample made slightly wider than lower one so two samples remain in complete contact even under slight lateral misalignment.

8. Measurement of heat conduction through stacked screens

NASA Technical Reports Server (NTRS)

Lewis, M. A.; Kuriyama, T.; Kuriyama, F.; Radebaugh, R.

1998-01-01

This paper describes the experimental apparatus for the measurement of heat conduction through stacked screens as well as some experimental results taken with the apparatus. Screens are stacked in a fiberglass-epoxy cylinder, which is 24.4 mm in diameter and 55 mm in length. The cold end of the stacked screens is cooled by a Gifford-McMahon (GM) cryocooler at cryogenic temperature, and the hot end is maintained at room temperature. Heat conduction through the screens is determined from the temperature gradient in a calibrated heat flow sensor mounted between the cold end of the stacked screens and the GM cryocooler. The samples used for these experiments consisted of 400-mesh stainless steel screens, 400-mesh phosphor bronze screens, and two different porosities of 325-mesh stainless steel screens. The wire diameter of the 400-mesh stainless steel and phosphor bronze screens was 25.4 micrometers and the 325-mesh stainless steel screen wire diameters were 22.9 micrometers and 27.9 micrometers. Standard porosity values were used for the experimental data with additional porosity values used on selected experiments. The experimental results showed that the helium gas between each screen enhanced the heat conduction through the stacked screens by several orders of magnitude compared to that in vacuum. The conduction degradation factor is the ratio of actual heat conduction to the heat conduction where the regenerator material is assumed to be a solid rod of the same cross sectional area as the metal fraction of the screen. This factor was about 0.1 for the stainless steel and 0.022 for the phosphor bronze, and almost constant for the temperature range of 40 to 80 K at the cold end.

9. Thermal Conductivity Measurements on consolidated Soil Analogs

Seiferlin, K.; Heimberg, M.; Thomas, N.

2007-08-01

Heat transport in porous media such as soils and regolith is significantly reduced compared to the properties of compact samples of the same material. The bottle neck for solid state heat transport is the contact area between adjacent grains. For "dry" and unconsolidated materials the contact areas and thus the thermal conductivity are extremely small. Sintering and cementation are two processes that can increase the cross section of interstitial bonds signifcantly. On Mars, cementation can be caused by condensation of water or carbon dioxide ice from the vapor phase, or from salts and minerals that fall out from aqueous solutions. We produced several artificially cemented samples, using small glass beads of uniform size as soil analog. The cementation is achieved by initially molten wax that is mixed with the glass beads while liqiud. The wax freezes preferably at the contact points between grains, thus minimizing surface energy, and consolidates the samples. The thermal conductivity of these samples is then measured in vacuum. We present the results of these measurements and compare them with theoretical models. The observed range of thermal conductivity values can explain some, but not all of the variations in thermal intertia that can be seen in TES remote sensing data.

10. Signature of Topological Insulators in Conductance Measurements

Hong, Seokmin; Diep, Vinh; Datta, Supriyo

2012-02-01

Following the discovery of spin-polarized states at the surface of three-dimensional topological insulators (TI) like Bi2Te3 and Bi2Se3, there are intense interests in possible electrical measurements demonstrating unique signatures of these unusual states. A recent interesting proposal suggests that a signature of TI material should be a change in the conductance measured between a normal contact and a magnetic contact when the magnetization of the latter is reversed. However, the generalized Onsager relation suggests that no such change is expected in two-terminal setups and a multi-terminal set up is needed to observe the proposed effect. We present numerical results using a Non-Equilibrium Green Function (NEGF) based model capable of covering both ballistic and diffusive transport regimes seamlessly. Simple expressions based on a semi-classical picture describe some of the results quite well. Finally, we estimate the magnitude of signal expected in realistic samples that have recently been studied experimentally and have shown evidence of surface conduction.

11. Reflectometer distance measurement between parallel conductive plates

NASA Technical Reports Server (NTRS)

Hearn, Chase P.; Neece, Robert T.

1995-01-01

This report presents an analytic and experimental investigation of the measurement problem in which a reflectometer is used to determine the distance to a target that is a highly conductive surface parallel to the reflectometer antenna ground plane. These parallel surfaces constitute a waveguide (WG) which can contribute parasitic perturbations that seriously degrade the accuracy of the measurements. Two distinct parallel-plate-waveguide (PPWG) phenomena are described, and their effects on both frequency and time-domain reflectometers are considered. The time-domain processing approach was found to be superior to a representative frequency-domain phase-measurement approach because of less susceptibility to perturbations produced by edge reflections and immunity to phase capture. Experimental results are presented which show that a simple radiating system modification can suppress parallel-plate (PP) propagation. The addition of a thin layer of lossy mu-metal 'magnetic absorber' to the antenna ground plane allowed a measurement accuracy of 0.025 cm (0.01 in.) when a vector network analyzer (VNA) is used as a time-domain reflectometer.

12. Measuring Thermal Conductivity at LH2 Temperatures

NASA Technical Reports Server (NTRS)

Selvidge, Shawn; Watwood, Michael C.

2004-01-01

For many years, the National Institute of Standards and Technology (NIST) produced reference materials for materials testing. One such reference material was intended for use with a guarded hot plate apparatus designed to meet the requirements of ASTM C177-97, "Standard Test Method for Steady-State Heat Flux Measurements and Thermal Transmission Properties by Means of the Guarded-Hot-Plate Apparatus." This apparatus can be used to test materials in various gaseous environments from atmospheric pressure to a vacuum. It allows the thermal transmission properties of insulating materials to be measured from just above ambient temperature down to temperatures below liquid hydrogen. However, NIST did not generate data below 77 K temperature for the reference material in question. This paper describes a test method used at NASA's Marshall Space Flight Center (MSFC) to optimize thermal conductivity measurements during the development of thermal protection systems. The test method extends the usability range of this reference material by generating data at temperatures lower than 77 K. Information provided by this test is discussed, as are the capabilities of the MSFC Hydrogen Test Facility, where advanced methods for materials testing are routinely developed and optimized in support of aerospace applications.

13. Measuring Cavitation with Synchrotron X-Rays

Duke, Daniel; Kastengren, Alan; Powell, Chris; X-Ray Fuel Spray Group, Energy Systems Division Team

2012-11-01

Cavitation plays an important role in the formation of sprays from small nozzles such as those found in fuel injection systems. A sharp-edged inlet from the sac into the nozzle of a diesel fuel injector is shown to inititate a strong sheet-like cavitation along the boundary layer of the nozzle throat, which is difficult to measure and can lead to acoustic damage. To investigate this phenomenon, a diagnostic technique capable of mapping the density field of the nozzle through regions of intense cavitation is required. Available visible-light techniques are limited to qualitative observations of the outer extent of cavitation zones. However, brilliant X-rays from a synchrotron source have negligible refraction and are capable of penetrating the full extent of cavitation zones. We present the early results of a novel application of line-of-sight, time-resolved X-ray radiography on a cavitating model nozzle. Experiments were conducted at Sector 7-BM of the Advanced Photon Source. Density and vapor distribution are measured from the quantitative absorption of monochromatic X-rays. The density field can then be tomographically reconstructed from the projections. The density is then validated against a range of compressible and incompressible numerical simulations. This research was performed at the 7-BM beamline of the Advanced Photon Source. We acknowledge the support of the U.S. Department of Energy under Contract No. DE-AC02-06CH11357 and the DOE Vehicle Technologies Program (DOE-EERE).

14. Assessing Conduct Disorder: A New Measurement Approach

PubMed Central

Reavy, Racheal; Stein, L. A. R.; Quina, Kathryn; Paiva, Andrea L.

2015-01-01

The Delinquent Activities Scale (DAS) was used to develop indicators of conduct disorder (CD) in terms of symptom severity and age of onset. Incarcerated adolescents (N = 190) aged 14 to 19 were asked about their delinquent behaviors, including age the behavior was first performed, as well as substance use and parental and peer influences. Assessments were performed for the 12 months prior to incarceration and at 3-month postrelease follow-up. Evidence supports the utility of the DAS as a measure of CD diagnosis, including concurrent incremental validity. Furthermore, CD severity (symptom count) was significantly associated with two peer factors: friend substance use and friend prior arrests, with medium to large effect sizes (ESs). Earlier age of CD onset was associated with earlier marijuana use. This study finds that the DAS is a useful instrument in that it is easy to apply and has adequate psychometrics. PMID:24241820

15. Sensitive bridge circuit measures conductance of low-conductivity electrolyte solutions

NASA Technical Reports Server (NTRS)

Schmidt, K.

1967-01-01

Compact bridge circuit measures sensitive and accurate conductance of low-conductivity electrolyte solutions. The bridge utilizes a phase sensitive detector to obtain a linear deflection of the null indicator relative to the measured conductance.

16. 21 CFR 882.1550 - Nerve conduction velocity measurement device.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Nerve conduction velocity measurement device. 882... conduction velocity measurement device. (a) Identification. A nerve conduction velocity measurement device is a device which measures nerve conduction time by applying a stimulus, usually to a...

17. 21 CFR 882.1550 - Nerve conduction velocity measurement device.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Nerve conduction velocity measurement device. 882... conduction velocity measurement device. (a) Identification. A nerve conduction velocity measurement device is a device which measures nerve conduction time by applying a stimulus, usually to a...

18. 21 CFR 882.1550 - Nerve conduction velocity measurement device.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Nerve conduction velocity measurement device. 882... conduction velocity measurement device. (a) Identification. A nerve conduction velocity measurement device is a device which measures nerve conduction time by applying a stimulus, usually to a...

19. 21 CFR 882.1550 - Nerve conduction velocity measurement device.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Nerve conduction velocity measurement device. 882... conduction velocity measurement device. (a) Identification. A nerve conduction velocity measurement device is a device which measures nerve conduction time by applying a stimulus, usually to a...

20. 21 CFR 882.1550 - Nerve conduction velocity measurement device.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Nerve conduction velocity measurement device. 882... conduction velocity measurement device. (a) Identification. A nerve conduction velocity measurement device is a device which measures nerve conduction time by applying a stimulus, usually to a...

1. Thermal conductivity measurements of proton-heated warm dense matter

McKelvey, A.; Fernandez-Panella, A.; Hua, R.; Kim, J.; King, J.; Sio, H.; McGuffey, C.; Kemp, G. E.; Freeman, R. R.; Beg, F. N.; Shepherd, R.; Ping, Y.

2015-06-01

Accurate knowledge of conductivity characteristics in the strongly coupled plasma regime is extremely important for ICF processes such as the onset of hydrodynamic instabilities, thermonuclear burn propagation waves, shell mixing, and efficient x-ray conversion of indirect drive schemes. Recently, an experiment was performed on the Titan laser platform at the Jupiter Laser Facility to measure the thermal conductivity of proton-heated warm dense matter. In the experiment, proton beams generated via target normal sheath acceleration were used to heat bi-layer targets with high-Z front layers and lower-Z back layers. The stopping power of a material is approximately proportional to Z2 so a sharp temperature gradient is established between the two materials. The subsequent thermal conduction from the higher-Z material to the lower-Z was measured with time resolved streaked optical pyrometry (SOP) and Fourier domain interferometry (FDI) of the rear surface. Results will be used to compare predictions from the thermal conduction equation and the Wiedemann-Franz Law in the warm dense matter regime. Data from the time resolved diagnostics for Au/Al and Au/C Targets of 20-200 nm thickness will be presented.

2. Underground measurements on secondary cosmic rays

NASA Technical Reports Server (NTRS)

Fenton, A. G.; Wilson, C. W.; Fenton, K. B.

1985-01-01

Measurements made at the Poatina cosmic ray station (41.8 S 149.9 E, 347 m.w.e.) from August 1983 to July 1984 are summarized. The cosmic ray primary particles responsible for events detected at the station have a median primary energy of 1.2 TeV. The motivation for part of this work came from the reported detection of narrow angle anisotropies in the arrival direction of cosmic rays.

3. Quantitative Measurements of X-ray Intensity

SciTech Connect

Haugh, M. J., Schneider, M.

2011-09-01

This chapter describes the characterization of several X-ray sources and their use in calibrating different types of X-ray cameras at National Security Technologies, LLC (NSTec). The cameras are employed in experimental plasma studies at Lawrence Livermore National Laboratory (LLNL), including the National Ignition Facility (NIF). The sources provide X-rays in the energy range from several hundred eV to 110 keV. The key to this effort is measuring the X-ray beam intensity accurately and traceable to international standards. This is accomplished using photodiodes of several types that are calibrated using radioactive sources and a synchrotron source using methods and materials that are traceable to the U.S. National Institute of Standards and Technology (NIST). The accreditation procedures are described. The chapter begins with an introduction to the fundamental concepts of X-ray physics. The types of X-ray sources that are used for device calibration are described. The next section describes the photodiode types that are used for measuring X-ray intensity: power measuring photodiodes, energy dispersive photodiodes, and cameras comprising photodiodes as pixel elements. Following their description, the methods used to calibrate the primary detectors, the power measuring photodiodes and the energy dispersive photodiodes, as well as the method used to get traceability to international standards are described. The X-ray source beams can then be measured using the primary detectors. The final section then describes the use of the calibrated X-ray beams to calibrate X-ray cameras. Many of the references are web sites that provide databases, explanations of the data and how it was generated, and data calculations for specific cases. Several general reference books related to the major topics are included. Papers expanding some subjects are cited.

4. Electrical conduction and photoresponses of gamma-ray-irradiated single-stranded DNA/single-walled carbon nanotube composite systems

Hong, W.; Lee, E. M.; Kim, D. W.; Lee, Cheol Eui

2015-04-01

Effects of gamma-ray irradiation on the electrical conductivity and photoresponse have been studied for single-stranded DNA (ssDNA)/single-walled carbon nanotube (SWNT) composite films. The temperature-dependent electrical conductivity of the ssDNA/SWNT composite films, well described by a fluctuation-induced tunneling model, indicated modification of the barrier for thermally activated conduction by the gamma-ray irradiation. Besides, the photoresponse measurements indicated modified photoexcited charge carrier generation and oxygen photodesorption in the composite systems due to the gamma-ray irradiation.

5. Phase transitions in U3O8- z: II. Electrical conductivity measurement

Naito, Keiji; Tsuji, Toshihide; Ohya, Fumiaki

1983-02-01

Phase transition in U3O8- z was studied by means of electrical conductivity measurement and X-ray diffraction technique in the temperature range from room temperature to 1073 K. It was found that the break in a linear relation between the electrical conductivity and the reciprocal temperature which corresponds to the phase transition varies with the O/U ratio, the heat treatment of the sample and the heating rate during the electrical conductivity measurement. From the electrical conductivity and X-ray diffraction studies, phase transition in  U3O8- z is concluded to be an order-disorder type based on the configurational change of U(V) and U(VI) ions with structural changes from orthorhombic to hexagonal. A phase diagram in U3O8- z was proposed from the electrical conductivity, X-ray diffraction and heat capacity data.

6. Scattering from conducting open cavities by generalized ray expansion (GRE)

Garcia-Pino, Antonio; Obelleiro, Fernando; Rodriguez, Jose L.

1993-07-01

The problem of electromagnetic (EM) scattering by metallic open cavities is addressed here using a generalized ray expansion (GRE) method. The wave coupled into the cavity is modeled as a combination of a number of spherical waves, the propagation of such waves being described in terms of geometrical optics (GO). A brief description of the method including some details about aperture discretization as well as results for three-dimensional problems such as circular and rectangular cross-section cavities are presented. The GRE method gives results that agree well with those of modal analysis and allow, like ray methods, for greater flexibility in geometric modeling. Furthermore, the ray-tracing process must be done only once for different incident waves, so its computational cost is lower than that of the classic ray methods, where the incoming wave is described as a different bundle of parallel rays for each direction of incidence.

7. Energy loss measurement of cosmic ray muons

Unger, Joseph

1993-02-01

Measurements of energy losses of high energy cosmic ray muons in an ionization chamber are presented. The chamber consists of 16 single gap layers, and the liquid tetra methyl silane (TMS) was used as active medium. The absolute energy loss and the relativistic rise were measured and compared with theoretical calculations. The importance of the measurements within the framework of the cosmic ray experiment KASCADE (German acronym for Karlsruhe Shower Core and Array Detector) are discussed, especially with respect to energy calibration of hadrons and high energy muons above 1 TeV.

8. Non-Contact Electrical Conductivity Measurement Technique for Molten Metals

NASA Technical Reports Server (NTRS)

Rhim, W. K.; Ishikawa, T.

1998-01-01

A non-contact technique of measuring the electrical conductivity (or resistivity) of conducting liquids while they are levitated by the high temperature electrostatic levitator in a high vacuum is reported.

9. Ac-electrical conductivity of poly(propylene) before and after X-ray irradiation

Gaafar, M.

2001-05-01

10. Measurement of the thermal contact conductance and thermal conductivity of anodized aluminum coatings

SciTech Connect

Peterson, G.P.; Fletcher, L.S. )

1990-08-01

An experimental investigation was conducted to determine the thermal contact conductance and effective thermal conductivity of anodized coatings. One chemically polished Aluminum 6061-T6 test specimen and seven specimens with anodized coatings varying in thickness from 60.9 {mu}m to 163.8 {mu}m were tested while in contact with a single unanodized aluminum surface. Measurements of the overall joint conductance, composed of the thermal contact conductance between the anodized coating and the bare aluminum surface and the bulk conductance of the coating material, indicated that the overall joint conductance decreased with increasing thickness of the anodized coating and increased with increasing interfacial load. Using the experimental data, a dimensionless expression was developed that related the overall joint conductance to the coating thickness, the surface roughness, the interfacial pressure, and the properties of the aluminum substrate. By subtracting the thermal contact conductance from the measured overall joint conductance, estimations of the effective thermal conductivity of the anodized coating as a function of pressure were obtained for each of the seven anodized specimens. At an extrapolated pressure of zero, the effective thermal conductivity was found to be approximately 0.02 W/m-K. In addition to this extrapolated value, a single expression for predicting the effective thermal conductivity as a function of both the interface pressure and the anodized coating thickness was developed and shown to be within {plus minus}5 percent of the experimental data over a pressure range of 0 to 14 MPa.

11. Measuring Flash X-Ray Spectra with a Compton Spectrometer

Gehring, Amanda; Espy, Michelle; Haines, Todd; Hunter, James; King, Nick; Merrill, Frank; Sedillo, Robert; Urbaitis, Algis; Volegov, Petr

2014-09-01

The determination of the x-ray energy spectra of flash radiographic sources is difficult due to the short nature of the pulses (~50 ns). Recently, a Compton spectrometer has been refurbished and investigated as a potential device for conducting these measurements. The spectrometer was originally designed and characterized by Morgan et al.. The spectrometer consists of a 300 kg neodymium-iron magnet and measures spectra in the <1 MeV to 20 MeV energy range. In this apparatus, the incoming x-rays are collimated into a narrow beam before encountering a converter foil. Compton electrons are ejected and collimated so that the forward-directed electrons enter the magnetic field region of the device. The position of the electrons on the magnet focal plane is a function of their energy, allowing the x-ray spectrum to be reconstructed. Recent energy calibration measurements and the spectrum reconstruction of a Bremsstrahlung source will be presented. The determination of the x-ray energy spectra of flash radiographic sources is difficult due to the short nature of the pulses (~50 ns). Recently, a Compton spectrometer has been refurbished and investigated as a potential device for conducting these measurements. The spectrometer was originally designed and characterized by Morgan et al.. The spectrometer consists of a 300 kg neodymium-iron magnet and measures spectra in the <1 MeV to 20 MeV energy range. In this apparatus, the incoming x-rays are collimated into a narrow beam before encountering a converter foil. Compton electrons are ejected and collimated so that the forward-directed electrons enter the magnetic field region of the device. The position of the electrons on the magnet focal plane is a function of their energy, allowing the x-ray spectrum to be reconstructed. Recent energy calibration measurements and the spectrum reconstruction of a Bremsstrahlung source will be presented. LA-UR-14-23602.

12. Gamma-ray multiplicity measurements using STEFF

Pollitt, A. J.; Smith, A. G.; Tsekhanovich, I.; Dare, J. A.

2012-09-01

An ongoing investigation into the angular momentum generated during the fission of 252Cf is currently under way using the SpecTrometer for Exotic Fission Fragments (STEFF). Measurements have been made of the fold distribution (measured multiplicity) with STEFF. These have been compared to a Monte-carlo simulation to determine a value for the average angular momentum Jrms = 6hslash which is comparable to previous measurements [1]. Measurements of the gamma-ray multiplicity were performed whilst gating on different fragment mass regions. The result was compared with a sum of the lowest 2+ energies from both fragment and complementary in the mass gate. The results support the view that gamma-ray multiplicity is largely determined by the decay of the nucleus through near yrast transitions that follow the statistical decay.

13. Differential heating: A versatile method for thermal conductivity measurements in high-energy-density matter

DOE PAGESBeta

Ping, Y.; Fernandez-Panella, A.; Sio, H.; Correa, A.; Shepherd, R.; Landen, O.; London, R. A.; Sterne, P. A.; Whitley, H. D.; Fratanduono, D.; et al

2015-09-04

We propose a method for thermal conductivity measurements of high energy density matter based on differential heating. A temperature gradient is created either by surface heating of one material or at an interface between two materials by different energy deposition. The subsequent heat conduction across the temperature gradient is observed by various time-resolved probing techniques. Conceptual designs of such measurements using laser heating, proton heating, and x-ray heating are presented. As a result, the sensitivity of the measurements to thermal conductivity is confirmed by simulations.

14. Differential heating: A versatile method for thermal conductivity measurements in high-energy-density matter

SciTech Connect

Ping, Y.; Fernandez-Panella, A.; Correa, A.; Shepherd, R.; Landen, O.; London, R. A.; Sterne, P. A.; Whitley, H. D.; Fratanduono, D.; Collins, G. W.; Sio, H.; Boehly, T. R.

2015-09-15

We propose a method for thermal conductivity measurements of high energy density matter based on differential heating. A temperature gradient is created either by surface heating of one material or at an interface between two materials by different energy deposition. The subsequent heat conduction across the temperature gradient is observed by various time-resolved probing techniques. Conceptual designs of such measurements using laser heating, proton heating, and x-ray heating are presented. The sensitivity of the measurements to thermal conductivity is confirmed by simulations.

15. Determining the Uncertainty of X-Ray Absorption Measurements

PubMed Central

Wojcik, Gary S.

2004-01-01

X-ray absorption (or more properly, x-ray attenuation) techniques have been applied to study the moisture movement in and moisture content of materials like cement paste, mortar, and wood. An increase in the number of x-ray counts with time at a location in a specimen may indicate a decrease in moisture content. The uncertainty of measurements from an x-ray absorption system, which must be known to properly interpret the data, is often assumed to be the square root of the number of counts, as in a Poisson process. No detailed studies have heretofore been conducted to determine the uncertainty of x-ray absorption measurements or the effect of averaging data on the uncertainty. In this study, the Poisson estimate was found to adequately approximate normalized root mean square errors (a measure of uncertainty) of counts for point measurements and profile measurements of water specimens. The Poisson estimate, however, was not reliable in approximating the magnitude of the uncertainty when averaging data from paste and mortar specimens. Changes in uncertainty from differing averaging procedures were well-approximated by a Poisson process. The normalized root mean square errors decreased when the x-ray source intensity, integration time, collimator size, and number of scanning repetitions increased. Uncertainties in mean paste and mortar count profiles were kept below 2 % by averaging vertical profiles at horizontal spacings of 1 mm or larger with counts per point above 4000. Maximum normalized root mean square errors did not exceed 10 % in any of the tests conducted. PMID:27366627

16. Neutron and Gamma-ray Measurements

Krasilnikov, Anatoly V.; Sasao, Mamiko; Kaschuck, Yuri A.; Kiptily, Vasily G.; Nishitani, Takeo; Popovichev, Sergey V.; Bertalot, Luciano

2008-03-01

Due to high neutron and gamma-ray yields and large size plasmas many future fusion reactor plasma parameters such as fusion power, fusion power density, ion temperature, fuel mixture, fast ion energy and spatial distributions can be well measured by various fusion product diagnostics. Neutron diagnostics provide information on fusion reaction rate, which indicates how close is the plasma to the ultimate goal of nuclear fusion and fusion power distribution in the plasma core, which is crucial for optimization of plasma breakeven and burn. Depending on the plasma conditions neutron and gamma-ray diagnostics can provide important information, namely about dynamics of fast ion energy and spatial distributions during neutral beam injection, ion cyclotron heating and generated by fast ions MHD instabilities. The influence of the fast particle population on the 2-D neutron source profile was clearly demonstrated in JET experiments. 2-D neutron and gamma-ray source measurements could be important for driven plasma heating profile optimization in fusion reactors. To meat the measurement requirements in ITER the planned set of neutron and gamma ray diagnostics includes radial and vertical neutron and gamma cameras, neutron flux monitors, neutron activation systems and neutron spectrometers. The necessity of using massive radiation shielding strongly influences the diagnostic designs in fusion reactor, determines angular fields of view of neutron and gamma-ray cameras and spectrometers and gives rise to unavoidable difficulties in the absolute calibration. The development, testing in existing tokomaks and a possible engineering integration of neuron and gamma-ray diagnostic systems into ITER are presented.

17. Measuring the local electrical conductivity of human brain tissue

Akhtari, M.; Emin, D.; Ellingson, B. M.; Woodworth, D.; Frew, A.; Mathern, G. W.

2016-02-01

The electrical conductivities of freshly excised brain tissues from 24 patients were measured. The diffusion-MRI of the hydrogen nuclei of water molecules from regions that were subsequently excised was also measured. Analysis of these measurements indicates that differences between samples' conductivities are primarily due to differences of their densities of solvated sodium cations. Concomitantly, the sample-to-sample variations of their diffusion constants are relatively small. This finding suggests that non-invasive in-vivo measurements of brain tissues' local sodium-cation density can be utilized to estimate its local electrical conductivity.

18. Comparison of Measured and Estimated Unsaturated Hydraulic Conductivity

Parkes, M. E.; Waters, P. A.

1980-08-01

Most studies of empirical estimates of unsaturated hydraulic conductivity functions do not account for water which may be relatively immobile under the conditions in which field measurements of conductivity are made. To investigate this, unsaturated hydraulic conductivity data were obtained for three monolith lysimeters, 80 cm in diameter by 135 cm deep, using the instantaneous profile technique. The lysimeters contained well-structured, freely draining loam soil and moisture measurements were made using a neutron probe. Conductivity estimates were also obtained from laboratory measurements of soil moisture characteristics using the modified Millington and Quirk computational method. Ratios of the calculated to measured conductivities at a matching point near saturation were so large as to suggest that only a minor proportion of the soil pore space was contributing to flow through the whole profile.

19. X-ray Pinhole Camera Measurements

SciTech Connect

Nelson, D. S.; Berninger, M. J.; Flores, P. A.; Good, D. E.; Henderson, D. J.; Hogge, K. W.; Huber, S. R.; Lutz, S. S.; Mitchell, S. E.; Howe, R. A.; Mitton, C. V.; Molina, I.; Bozman, D. R.; Cordova, S. R.; Mitchell, D. R.; Oliver, B. V.; Ormond, E. C.

2013-07-01

The development of the rod pinch diode [1] has led to high-resolution radiography for dynamic events such as explosive tests. Rod pinch diodes use a small diameter anode rod, which extends through the aperture of a cathode plate. Electrons borne off the aperture surface can self-insulate and pinch onto the tip of the rod, creating an intense, small x-ray source (Primary Pinch). This source has been utilized as the main diagnostic on numerous experiments that include high-value, single-shot events. In such applications there is an emphasis on machine reliability, x-ray reproducibility, and x-ray quality [2]. In tests with the baseline rod pinch diode, we have observed that an additional pinch (Secondary Pinch) occurs at the interface near the anode rod and the rod holder. This suggests that stray electrons exist that are not associated with the Primary Pinch. In this paper we present measurements on both pinches using an x-ray pinhole camera. The camera is placed downstream of the Primary Pinch at an angle of 60° with respect to the diode centerline. This diagnostic will be employed to diagnose x-ray reproducibility and quality. In addition, we will investigate the performance of hybrid diodes relating to the formation of the Primary and Secondary Pinches.

20. Thin conductive diamond films as beam intensity monitors for soft x-ray beamlines.

PubMed

Kummer, K; Fondacaro, A; Yakhou-Harris, F; Sessi, V; Pobedinskas, P; Janssens, S D; Haenen, K; Williams, O A; Hees, J; Brookes, N B

2013-03-01

Quantitative analysis of X-ray absorption and dichroism data requires knowledge of the beamline photon flux during the measurements. We show that thin conductive (B-doped) diamond thin films can be an alternative to the widely used gold meshes for monitoring the beam intensity of soft X-ray beamlines in situ. Limited by the carbon extended x-ray absorption fine structure oscillations, the diamond films become applicable beginning from about 600 eV photon energy, where the important transition metal edges and the rare-earth edges are found. The 100 nm and 250 nm thick free-standing diamond films were grown and tested against standard gold meshes in real-life dichroism experiments performed at beamline ID08 of the European Synchrotron Radiation Facility, Grenoble, France. Quantitative agreement was found between the two experimental data sets. The films feature an extremely high transmission of about 90% and, at the same time, yield a sufficiently strong and clean reference signal. Furthermore, the thin films do not affect the shape of the transmitted beam. X-rays passing mesh-type monitors are subject to diffraction effects, which widen the beam and become particularly disturbing for small beamsizes in the micrometer range. PMID:23556850

1. Thin conductive diamond films as beam intensity monitors for soft x-ray beamlines

SciTech Connect

Kummer, K.; Fondacaro, A.; Yakhou-Harris, F.; Sessi, V.; Brookes, N. B.; Pobedinskas, P.; Janssens, S. D.; Haenen, K.; Williams, O. A.; Hees, J.

2013-03-15

Quantitative analysis of X-ray absorption and dichroism data requires knowledge of the beamline photon flux during the measurements. We show that thin conductive (B-doped) diamond thin films can be an alternative to the widely used gold meshes for monitoring the beam intensity of soft X-ray beamlines in situ. Limited by the carbon extended x-ray absorption fine structure oscillations, the diamond films become applicable beginning from about 600 eV photon energy, where the important transition metal edges and the rare-earth edges are found. The 100 nm and 250 nm thick free-standing diamond films were grown and tested against standard gold meshes in real-life dichroism experiments performed at beamline ID08 of the European Synchrotron Radiation Facility, Grenoble, France. Quantitative agreement was found between the two experimental data sets. The films feature an extremely high transmission of about 90% and, at the same time, yield a sufficiently strong and clean reference signal. Furthermore, the thin films do not affect the shape of the transmitted beam. X-rays passing mesh-type monitors are subject to diffraction effects, which widen the beam and become particularly disturbing for small beamsizes in the micrometer range.

2. X ray based displacement measurement for hostile environments

NASA Technical Reports Server (NTRS)

Canistraro, Howard A.; Jordon, Eric H.; Pease, Douglas M.; Fralick, Gustave C.

1992-01-01

A new method on noncontacting, high temperature extensometry based on the focus and scanning of x rays is currently under development and shows great promise of overcoming limitations associated with available techniques. The chief advantage is the ability to make undisturbed measurements through stratified or flowing gases, smoke, and flame. The system is based on the ability to focus and scan low energy, hard x rays such as those emanating from copper or molybdenum sources. The x rays are focused into a narrow and intense line image which can be scanned onto targets that fluoresce secondary x ray radiation. The final goal of the system is the ability to conduct macroscopic strain measurements in hostile environments by utilizing two or more fluorescing targets. Current work is limited to displacement measurement of a single target with a resolution of 1.25 micro-m and a target temperature of 1200 C, directly through an open flame. The main advantage of the technique lies in the penetrating nature of x rays which are not affected by the presence of refracting gas layers, smoke, flame, or intense thermal radiation, all of which could render conventional extensometry methods inoperative or greatly compromise their performance.

3. X-ray-based displacement measurement for hostile environments

NASA Technical Reports Server (NTRS)

Canistraro, H. A.; Jordan, E. H.; Pease, D. M.

1992-01-01

A new method on noncontacting, high temperature extensometry based on the focus and scanning of X-rays is currently under development and shows great promise of overcoming limitations associated with available techniques. The chief advantage is the ability to make undisturbed measurements through stratified or flowing gases, smoke, and flame. The system is based on the ability to focus and scan low energy, hard X-rays such as those emanating from copper or molybdenum sources. The X-rays are focused into a narrow and intense line image which can be scanned onto targets that fluoresce secondary X-ray radiation. The final goal of the system is the ability to conduct macroscopic strain measurements in hostile environments by utilizing two or more fluorescing targets. Current work is limited to displacement measurement of a single target with a resolution of 1.25 micro-m and a target temperature of 1200 C, directly through an open flame. The main advantage of the technique lies in the penetrating nature of X-rays which are not affected by the presence of refracting gas layers, smoke, flame, or intense thermal radiation, all of which could render conventional extensometry methods inoperative or greatly compromise their performance.

4. In situ measurement of conductivity during nanocomposite film deposition

Blattmann, Christoph O.; Pratsinis, Sotiris E.

2016-05-01

Flexible and electrically conductive nanocomposite films are essential for small, portable and even implantable electronic devices. Typically, such film synthesis and conductivity measurement are carried out sequentially. As a result, optimization of filler loading and size/morphology characteristics with respect to film conductivity is rather tedious and costly. Here, freshly-made Ag nanoparticles (nanosilver) are made by scalable flame aerosol technology and directly deposited onto polymeric (polystyrene and poly(methyl methacrylate)) films during which the resistance of the resulting nanocomposite is measured in situ. The formation and gas-phase growth of such flame-made nanosilver, just before incorporation onto the polymer film, is measured by thermophoretic sampling and microscopy. Monitoring the nanocomposite resistance in situ reveals the onset of conductive network formation by the deposited nanosilver growth and sinternecking. The in situ measurement is much faster and more accurate than conventional ex situ four-point resistance measurements since an electrically percolating network is detected upon its formation by the in situ technique. Nevertheless, general resistance trends with respect to filler loading and host polymer composition are consistent for both in situ and ex situ measurements. The time lag for the onset of a conductive network (i.e., percolation) depends linearly on the glass transition temperature (Tg) of the host polymer. This is attributed to the increased nanoparticle-polymer interaction with decreasing Tg. Proper selection of the host polymer in combination with in situ resistance monitoring therefore enable the optimal preparation of conductive nanocomposite films.

5. Measurement of thermal conductivity in proton irradiated silicon

SciTech Connect

Marat Khafizov; Clarissa Yablinsky; Todd Allen; David Hurley

2014-04-01

We investigate the influence of proton irradiation on thermal conductivity in single crystal silicon. We apply laser based modulated thermoreflectance technique to extract the change in conductivity of the thin layer damaged by proton irradiation. Unlike time domain thermoreflectance techniques that require application of a metal film, we perform our measurement on uncoated samples. This provides greater sensitivity to the change in conductivity of the thin damaged layer. Using sample temperature as a parameter provides a means to deduce the primary defect structures that limit thermal transport. We find that under high temperature irradiation the degradation of thermal conductivity is caused primarily by extended defects.

6. Thermal conductivity of halide solid solutions: measurement and prediction.

PubMed

Gheribi, Aïmen E; Poncsák, Sándor; St-Pierre, Rémi; Kiss, László I; Chartrand, Patrice

2014-09-14

The composition dependence of the lattice thermal conductivity in NaCl-KCl solid solutions has been measured as a function of composition and temperature. Samples with systematically varied compositions were prepared and the laser flash technique was used to determine the thermal diffusivity from 373 K to 823 K. A theoretical model, based on the Debye approximation of phonon density of state (which contains no adjustable parameters) was used to predict the thermal conductivity of both stoichiometric compounds and fully disordered solid solutions. The predictions obtained with the model agree very well with our measurement. A general method for predicting the thermal conductivity of different halide systems is discussed. PMID:25217938

7. Measurements of prompt radiation induced conductivity of Kapton.

SciTech Connect

Preston, Eric F.; Zarick, Thomas Andrew; Sheridan, Timothy J.; Hartman, E. Frederick; Stringer, Thomas Arthur

2010-10-01

We performed measurements of the prompt radiation induced conductivity in thin samples of Kapton (polyimide) at the Little Mountain Medusa LINAC facility in Ogden, UT. Three mil samples were irradiated with a 0.5 {mu}s pulse of 20 MeV electrons, yielding dose rates of 1E9 to 1E10 rad/s. We applied variable potentials up to 2 kV across the samples and measured the prompt conduction current. Analysis rendered prompt conductivity coefficients between 6E-17 and 2E-16 mhos/m per rad/s, depending on the dose rate and the pulse width.

8. Indirect measurement of thermal conductivity in silicon nanowires

SciTech Connect

Pennelli, Giovanni Nannini, Andrea; Macucci, Massimo

2014-02-28

We report indirect measurements of thermal conductivity in silicon nanostructures. We have exploited a measurement technique based on the Joule self-heating of silicon nanowires. A standard model for the electron mobility has been used to determine the temperature through the accurate measurement of the nanowire resistance. We have applied this technique to devices fabricated with a top-down process that yields nanowires together with large silicon areas used both as electrical and as thermal contacts. As there is crystalline continuity between the nanowires and the large contact areas, our thermal conductivity measurements are not affected by any temperature drop due to the contact thermal resistance. Our results confirm the observed reduction of thermal conductivity in nanostructures and are comparable with those previously reported in the literature, achieved with more complex measurement techniques.

9. Non-Contact Conductivity Measurement for Automated Sample Processing Systems

NASA Technical Reports Server (NTRS)

Beegle, Luther W.; Kirby, James P.

2012-01-01

A new method has been developed for monitoring and control of automated sample processing and preparation especially focusing on desalting of samples before analytical analysis (described in more detail in Automated Desalting Apparatus, (NPO-45428), NASA Tech Briefs, Vol. 34, No. 8 (August 2010), page 44). The use of non-contact conductivity probes, one at the inlet and one at the outlet of the solid phase sample preparation media, allows monitoring of the process, and acts as a trigger for the start of the next step in the sequence (see figure). At each step of the muti-step process, the system is flushed with low-conductivity water, which sets the system back to an overall low-conductivity state. This measurement then triggers the next stage of sample processing protocols, and greatly minimizes use of consumables. In the case of amino acid sample preparation for desalting, the conductivity measurement will define three key conditions for the sample preparation process. First, when the system is neutralized (low conductivity, by washing with excess de-ionized water); second, when the system is acidified, by washing with a strong acid (high conductivity); and third, when the system is at a basic condition of high pH (high conductivity). Taken together, this non-contact conductivity measurement for monitoring sample preparation will not only facilitate automation of the sample preparation and processing, but will also act as a way to optimize the operational time and use of consumables

10. Estimation of Ionospheric Conductivity Based on the Measurements by Superdarn

Lee, Eun-Ah; An, Byung-Ho; Yi, Yu

2002-06-01

The ionosphere plays an important role in the electrodynamics of space environment. In particular, the information on the ionospheric conductivity distribution is indispensable in understanding the electrodynamics of the magnetosphere and ionosphere coupling study. To meet such a requirement, several attempts have been made to estimate the conductivity distribution over the polar ionosphere. As one of such attempts we compare the ionospheric plasma convection patterns obtained from the Super Dual Auroral Radar Network (SuperDARN), from which the electric field distribution is estimated, and the simultaneously measured ground magnetic disturbance. Specifically, the electric field measured from the Goose Bay and Stokkseyri radars and magnetic disturbance data obtained from the west coast chain of Greenland are compared. In order to estimate ionospheric conductivity distribution with these information, the overhead infinite sheet current approximation is employed. As expected, the Hall conductance, height-integrated conductivity, shows a wide enhancement along the center of the auroral electrojet. However, Pedersen conductance shows negative values over a wide portion of the auroral oval region, a physically unacceptable situation. To alleviate this problem, the effect of the field-aligned current is taken into account. As a result, the region with negative Pedersen conductance disappears significantly, suggesting that the effect of the field-aligned current should be taken into account, when one wants to estimate ionospheric conductance based on ground magnetic disturbance and electric field measurements by radars.

11. In vivo electrical conductivity measurements during and after tumor electroporation: conductivity changes reflect the treatment outcome

Ivorra, Antoni; Al-Sakere, Bassim; Rubinsky, Boris; Mir, Lluis M.

2009-10-01

Electroporation is the phenomenon in which cell membrane permeability is increased by exposing the cell to short high-electric-field pulses. Reversible electroporation treatments are used in vivo for gene therapy and drug therapy while irreversible electroporation is used for tissue ablation. Tissue conductivity changes induced by electroporation could provide real-time feedback of the treatment outcome. Here we describe the results from a study in which fibrosarcomas (n = 39) inoculated in mice were treated according to different electroporation protocols, some of them known to cause irreversible damage. Conductivity was measured before, within the pulses, in between the pulses and for up to 30 min after treatment. Conductivity increased pulse after pulse. Depending on the applied electroporation protocol, the conductivity increase after treatment ranged from 10% to 180%. The most significant conclusion from this study is the fact that post-treatment conductivity seems to be correlated with treatment outcome in terms of reversibility.

12. A noncontact thermal microprobe for local thermal conductivity measurement.

PubMed

Zhang, Yanliang; Castillo, Eduardo E; Mehta, Rutvik J; Ramanath, Ganpati; Borca-Tasciuc, Theodorian

2011-02-01

We demonstrate a noncontact thermal microprobe technique for measuring the thermal conductivity κ with ∼3 μm lateral spatial resolution by exploiting quasiballistic air conduction across a 10-100 nm air gap between a joule-heated microprobe and the sample. The thermal conductivity is extracted from the measured effective thermal resistance of the microprobe and the tip-sample thermal contact conductance and radius in the quasiballistic regime determined by calibration on reference samples using a heat transfer model. Our κ values are within 5%-10% of that measured by standard steady-state methods and theoretical predictions for nanostructured bulk and thin film assemblies of pnictogen chalcogenides. Noncontact thermal microprobing demonstrated here mitigates the strong dependence of tip-sample heat transfer on sample surface chemistry and topography inherent in contact methods, and allows the thermal characterization of a wide range of nanomaterials. PMID:21361625

13. A noncontact thermal microprobe for local thermal conductivity measurement

Zhang, Yanliang; Castillo, Eduardo E.; Mehta, Rutvik J.; Ramanath, Ganpati; Borca-Tasciuc, Theodorian

2011-02-01

We demonstrate a noncontact thermal microprobe technique for measuring the thermal conductivity κ with ˜3 μm lateral spatial resolution by exploiting quasiballistic air conduction across a 10-100 nm air gap between a joule-heated microprobe and the sample. The thermal conductivity is extracted from the measured effective thermal resistance of the microprobe and the tip-sample thermal contact conductance and radius in the quasiballistic regime determined by calibration on reference samples using a heat transfer model. Our κ values are within 5%-10% of that measured by standard steady-state methods and theoretical predictions for nanostructured bulk and thin film assemblies of pnictogen chalcogenides. Noncontact thermal microprobing demonstrated here mitigates the strong dependence of tip-sample heat transfer on sample surface chemistry and topography inherent in contact methods, and allows the thermal characterization of a wide range of nanomaterials.

14. Measuring the conductivity dependence of the Casimir force

Xu, Jun; Schafer, Robert; Banishev, Alexandr; Mohideen, Umar

2015-03-01

The strength and distance dependence of the Casimir force can be controlled through the conductivity of the material bodies, with lower conductivity in general leading to lower Casimir forces. However low conductivity, large bandgap materials which are insulating, have drawbacks as any surface electrostatic charges cannot be easily compensated. This restricts experiments to metallic or highly doped semiconductor materials. We will report on measurements of the Casimir force gradient using the frequency shift technique. Improvements in the measurement technique will be discussed. Measurements of the Casimir force gradient using low and high conductivity silicon surfaces will be reported. The authors thank G.L. Klimchitskaya and V.M. Mostepanenko for help with the theory and the US National Science Foundation for funding the research.

15. Optical sensor for heat conduction measurement in biological tissue

Gutierrez-Arroyo, A.; Sanchez-Perez, C.; Aleman-Garcia, N.

2013-06-01

This paper presents the design of a heat flux sensor using an optical fiber system to measure heat conduction in biological tissues. This optoelectronic device is based on the photothermal beam deflection of a laser beam travelling in an acrylic slab this deflection is measured with a fiber optic angle sensor. We measure heat conduction in biological samples with high repeatability and sensitivity enough to detect differences in tissues from three chicken organs. This technique could provide important information of vital organ function as well as the detect modifications due to degenerative diseases or physical damage caused by medications or therapies.

16. pH measurement of low-conductivity waters

USGS Publications Warehouse

1987-01-01

pH is an important and commonly measured parameter of precipitation and other natural waters. The various sources of errors in pH measurement were analyzed and procedures for improving the accuracy and precision of pH measurements in natural waters with conductivities of < 100 uS/cm at 25 C are suggested. Detailed procedures are given for the preparation of dilute sulfuric acid standards to evaluate the performance of pH electrodes in low conductivity waters. A daily check of the pH of dilute sulfuric acid standards and deionized water saturated with a gas mixture of low carbon dioxide at partial pressure (air) prior to the measurement of the pH of low conductivity waters is suggested. (Author 's abstract)

17. Noninvasive measurement of conductivity anisotropy at larmor frequency using MRI.

PubMed

Lee, Joonsung; Song, Yizhuang; Choi, Narae; Cho, Sungmin; Seo, Jin Keun; Kim, Dong-Hyun

2013-01-01

Anisotropic electrical properties can be found in biological tissues such as muscles and nerves. Conductivity tensor is a simplified model to express the effective electrical anisotropic information and depends on the imaging resolution. The determination of the conductivity tensor should be based on Ohm's law. In other words, the measurement of partial information of current density and the electric fields should be made. Since the direct measurements of the electric field and the current density are difficult, we use MRI to measure their partial information such as B1 map; it measures circulating current density and circulating electric field. In this work, the ratio of the two circulating fields, termed circulating admittivity, is proposed as measures of the conductivity anisotropy at Larmor frequency. Given eigenvectors of the conductivity tensor, quantitative measurement of the eigenvalues can be achieved from circulating admittivity for special tissue models. Without eigenvectors, qualitative information of anisotropy still can be acquired from circulating admittivity. The limitation of the circulating admittivity is that at least two components of the magnetic fields should be measured to capture anisotropic information. PMID:23554838

18. Analytical estimation of skeleton thermal conductivity of a geopolymer foam from thermal conductivity measurements

Henon, J.; Alzina, A.; Absi, J.; Smith, D. S.; Rossignol, S.

2015-07-01

The geopolymers are alumino-silicate binders. The addition of a high pores volume fraction, gives them a thermal insulation character desired in the building industry. In this work, potassium geopolymer foams were prepared at room temperature (< 70 ∘C) by a process of in situ gas release. The porosity distribution shows a multiscale character. However, the thermal conductivity measurements gave values from 0.35 to 0.12 Wm-1.K-1 for a pore volume fraction values between 65 and 85%. In the aim to predict the thermal properties of these foams and focus on the relationship "thermal-conductivity/microstructure", knowledge of the thermal conductivity of their solid skeleton (λ s ) is paramount. However, there is rare work on the determination of this value depending on the initial composition. By the formulation used, the foaming agent contributes to the final network, and it is not possible to obtain a dense material designate to make a direct measurement of λ s . The objective of this work is to use inverse analytical methods to identify the value of λ s . Measurements of thermal conductivity by the fluxmetre technique were performed. The obtained value of the solid skeleton thermal conductivity by the inverse numerical technique is situated in a framework between 0.95 and 1.35 Wm-1.K-1 and is in agreement with one issue from the literature.

19. Thermal and Electrical Conductivity Measurements of CDA 510 Phosphor Bronze

NASA Technical Reports Server (NTRS)

Tuttle, James E.; Canavan, Edgar; DiPirro, Michael

2009-01-01

Many cryogenic systems use electrical cables containing phosphor bronze wire. While phosphor bronze's electrical and thermal conductivity values have been published, there is significant variation among different phosphor bronze formulations. The James Webb Space Telescope (JWST) will use several phosphor bronze wire harnesses containing a specific formulation (CDA 510, annealed temper). The heat conducted into the JWST instrument stage is dominated by these harnesses, and approximately half of the harness conductance is due to the phosphor bronze wires. Since the JWST radiators are expected to just keep the instruments at their operating temperature with limited cooling margin, it is important to know the thermal conductivity of the actual alloy being used. We describe an experiment which measured the electrical and thermal conductivity of this material between 4 and 295 Kelvin.

20. Method for Measuring Thermal Conductivity of Small Samples Having Very Low Thermal Conductivity

NASA Technical Reports Server (NTRS)

Miller, Robert A.; Kuczmarski, Maria a.

2009-01-01

This paper describes the development of a hot plate method capable of using air as a standard reference material for the steady-state measurement of the thermal conductivity of very small test samples having thermal conductivity on the order of air. As with other approaches, care is taken to ensure that the heat flow through the test sample is essentially one-dimensional. However, unlike other approaches, no attempt is made to use heated guards to block the flow of heat from the hot plate to the surroundings. It is argued that since large correction factors must be applied to account for guard imperfections when sample dimensions are small, it may be preferable to simply measure and correct for the heat that flows from the heater disc to directions other than into the sample. Experimental measurements taken in a prototype apparatus, combined with extensive computational modeling of the heat transfer in the apparatus, show that sufficiently accurate measurements can be obtained to allow determination of the thermal conductivity of low thermal conductivity materials. Suggestions are made for further improvements in the method based on results from regression analyses of the generated data.

1. In-Pile Thermal Conductivity Measurement Method for Nuclear Fuels

SciTech Connect

Joy L. Rempe; Brandon Fox; Heng Ban; Joshua E. Daw; Darrell L. Knudson; Keith G. Condie

2009-08-01

Thermophysical properties of advanced nuclear fuels and materials during irradiation must be known prior to their use in existing, advanced, or next generation reactors. Thermal conductivity is one of the most important properties for predicting fuel and material performance. A joint Utah State University (USU) / Idaho National Laboratory (INL) project, which is being conducted with assistance from the Institute for Energy Technology at the Norway Halden Reactor Project, is investigating in-pile fuel thermal conductivity measurement methods. This paper focuses on one of these methods – a multiple thermocouple method. This two-thermocouple method uses a surrogate fuel rod with Joule heating to simulate volumetric heat generation to gain insights about in-pile detection of thermal conductivity. Preliminary results indicated that this method can measure thermal conductivity over a specific temperature range. This paper reports the thermal conductivity values obtained by this technique and compares these values with thermal property data obtained from standard thermal property measurement techniques available at INL’s High Test Temperature Laboratory. Experimental results and material properties data are also compared to finite element analysis results.

2. In situ measurement of ceramic vacuum chamber conductive coating quality

SciTech Connect

Doose, C.; Harkay, K.; Kim, S.; Milton, S.

1997-08-01

A method for measuring the relative surface resistivity and quality of conductive coatings on ceramic vacuum chambers was developed. This method is unique in that it allows one to test the coating even after the ceramic chamber is installed in the accelerator and under vacuum; furthermore, the measurement provides a localized surface reading of the coating conductance. The method uses a magnetic probe is calibrated using the measured DC end-to-end resistance of the tube under test and by comparison to a high quality test surface. The measurement method has also been verified by comparison to high frequency impedance measurements. A detailed description, results, and sensitivity of the technique are given here.

3. Nerve conduction velocity measurements: improved accuracy using superimposed response waves.

PubMed

Halar, E M; Venkatesh, B

1976-10-01

A new procedure of serial motor nerve conduction velocity (NCV) measurements with the use of "superimposed response waves" technique (or double stimulus technique) was performed on 29 normal subjects. Six peripheral nerves were tested once a week for four to six weeks. A total of 760 NCV measurements were thus obtained to try to assess the magnitude of error in serial NCV testings. With the double stimulus technique employed, a significant reduction in variations of serial NCV measurements was found. The overall standard deviation of four to six consecutive NCV measurements in the 34 subjects was 1.3 meters per second with a coefficient of variation of 2.4%. These findings obtained with the double stimulus technique have proven to be approximately three times more accurate than results obtained by investigators who studied nerve conduction velocity measurement variation with single stimulus standard NCV testing techniques. PMID:184754

4. Measurement of thermal contact conductance of SPring-8 beamline components

Mochizuki, Tetsuro; Ohashi, Haruhiko; Sano, Mutsumi; Takahashi, Sunao; Goto, Shunji

2007-09-01

Direct cooling is adopted for most high heat load components in SPring-8 beamlines. On the other hand, contact cooling is employed for some components such as a graphite filter, aluminum filter, mirror, and cryogenic monochromator silicon crystal. For the thermal design of the contact cooling components, it is important to obtain reliable thermal contact conductance value. The conductance depends on many parameters such as the surface materials, surface roughness, flatness of the surface, interstitial materials, temperature of the contact surface, and contact pressure. An experimental setup is fablicated to measure the conductance at liquid nitrogen temperature and room temperature. The thermal contact conductance of a Si-Cu interface and that of a Si-In-Cu interface are measured at cryogenic temperature at contact pressures ranging from 0.1-1.1 MPa. The conductance of an Al-Cu interface and that of a graphite-Cu interface are measured using gold and silver foils as interstitial materials. The measurements are performed at room temperature and at pressures ranging from 0.5-4 MPa. The experimental setup and the results obtained are presented.

5. Measurements of prompt radiation induced conductivity in Teflon (PTFE).

SciTech Connect

Hartman, E. Frederick; Zarick, Thomas Andrew; Sheridan, Timothy J.; Preston, E.

2013-05-01

We performed measurements of the prompt radiation induced conductivity (RIC) in thin samples of Teflon (PTFE) at the Little Mountain Medusa LINAC facility in Ogden, UT. Three mil (76.2 microns) samples were irradiated with a 0.5 %CE%BCs pulse of 20 MeV electrons, yielding dose rates of 1E9 to 1E11 rad/s. We applied variable potentials up to 2 kV across the samples and measured the prompt conduction current. Details of the experimental apparatus and analysis are reported in this report on prompt RIC in Teflon.

6. VALIDATION OF A THERMAL CONDUCTIVITY MEASUREMENT SYSTEM FOR FUEL COMPACTS

SciTech Connect

Jeff Phillips; Colby Jensen; Changhu Xing; Heng Ban

2011-03-01

A high temperature guarded-comparative-longitudinal heat flow measurement system has been built to measure the thermal conductivity of a composite nuclear fuel compact. It is a steady-state measurement device designed to operate over a temperature range of 300 K to 1200 K. No existing apparatus is currently available for obtaining the thermal conductivity of the composite fuel in a non-destructive manner due to the compact’s unique geometry and composite nature. The current system design has been adapted from ASTM E 1225. As a way to simplify the design and operation of the system, it uses a unique radiative heat sink to conduct heat away from the sample column. A finite element analysis was performed on the measurement system to analyze the associated error for various operating conditions. Optimal operational conditions have been discovered through this analysis and results are presented. Several materials have been measured by the system and results are presented for stainless steel 304, inconel 625, and 99.95% pure iron covering a range of thermal conductivities of 10 W/m*K to 70 W/m*K. A comparison of the results has been made to data from existing literature.

7. Thermal Conductivity Measurements in Metals at High Pressures and Temperatures.

Konopkova, Z.; McWilliams, R. S.; Goncharov, A.

2014-12-01

The transport properties of iron and iron alloys at high pressures and temperatures are crucial parameters in planetary evolution models, yet are difficult to determine both theoretically and experimentally. Estimates of thermal conductivity in the Earth's core range from 30 to 150 W/mK, a substantial range leaving many open questions regarding the age of the inner core, the thermal structure of the outer core, and the conditions for a working geodynamo. Most experiments have measured electrical resistivity rather than directly measuring thermal conductivity, and have used models to extrapolate from low-temperature data to the high temperature conditions of the core. Here we present direct, in-situ high-pressure and high-temperature measurements of the thermal conductivity of metals in the diamond-anvil cell. Double-sided continuous laser heating is combined with one-side flash heating of a metallic foil, while the time-resolved temperature is measured from both sides with spectral radiometry in an optical streak camera. Emission and temperature perturbations measured on opposite sides of the foil were modeled using finite element calculations in order to extract thermal diffusivity and conductivity of foils. Results on platinum and iron at high pressures and temperatures will be presented.

8. Simultaneous specific heat and thermal conductivity measurement of individual nanostructures

Zheng, Jianlin; Wingert, Matthew C.; Moon, Jaeyun; Chen, Renkun

2016-08-01

Fundamental phonon transport properties in semiconductor nanostructures are important for their applications in energy conversion and storage, such as thermoelectrics and photovoltaics. Thermal conductivity measurements of semiconductor nanostructures have been extensively pursued and have enhanced our understanding of phonon transport physics. Specific heat of individual nanostructures, despite being an important thermophysical parameter that reflects the thermodynamics of solids, has remained difficult to characterize. Prior measurements were limited to ensembles of nanostructures in which coupling and sample inhomogeneity could play a role. Herein we report the first simultaneous specific heat and thermal conductivity measurements of individual rod-like nanostructures such as nanowires and nanofibers. This technique is demonstrated by measuring the specific heat and thermal conductivity of single ∼600–700 nm diameter Nylon-11 nanofibers (NFs). The results show that the thermal conductivity of the NF is increased by 50% over the bulk value, while the specific heat of the NFs exhibits bulk-like behavior. We find that the thermal diffusivity obtained from the measurement, which is related to the phonon mean free path (MFP), decreases with temperature, indicating that the intrinsic phonon Umklapp scattering plays a role in the NFs. This platform can also be applied to one- and two- dimensional semiconductor nanostructures to probe size effects on the phonon spectra and other transport physics.

9. Measurement of the anisotropic thermal conductivity of the porcine cornea.

PubMed

Barton, Michael D; Trembly, B Stuart

2013-10-01

Accurate thermal models for the cornea of the eye support the development of thermal techniques for reshaping the cornea and other scientific purposes. Heat transfer in the cornea must be quantified accurately so that a thermal treatment does not destroy the endothelial layer, which cannot regenerate, and yet is responsible for maintaining corneal transparency. We developed a custom apparatus to measure the thermal conductivity of ex vivo porcine corneas perpendicular to the surface and applied a commercial apparatus to measure thermal conductivity parallel to the surface. We found that corneal thermal conductivity is 14% anisotropic at the normal state of corneal hydration. Small numbers of ex vivo feline and human corneas had a thermal conductivity perpendicular to the surface that was indistinguishable from the porcine corneas. Aqueous humor from ex vivo porcine, feline, and human eyes had a thermal conductivity nearly equal to that of water. Including the anisotropy of corneal thermal conductivity will improve the predictive power of thermal models of the eye. PMID:23933570

10. Aqueous solubilities of phenol derivatives by conductivity measurements

SciTech Connect

Achard, C.; Jaoui, M.; Schwing, M.; Rogalski, M.

1996-05-01

The aqueous solubilities of five chlorophenols and three nitrophenols were measured by conductimetry at temperatures between 15 and 48C. The solubilities of 2-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, pentachlorophenol, 2-nitrophenol, 4-nitrophenol, and 2,4-dinitrophenol were studied. Automatic conductivity measurements allow the determination of the solute concentration and, hence, the determination of the solubility. Emulsion formation can also be followed. Results obtained are in good agreement with literature values.

11. Measurement of soil hydraulic conductivity in relation with vegetation

Chen, Xi; Cheng, Qinbo

2010-05-01

Hydraulic conductivity is a key parameter which influences hydrological processes of infiltration, surface and subsurface runoff. Vegetation alters surface characteristics (e.g., surface roughness, litter absorption) or subsurface characteristics (e.g. hydraulic conductivity). Field infiltration experiment of a single ring permeameter is widely used for measuring soil hydraulic conductivity. Measurement equipment is a simple single-ring falling head permeameter which consists of a hollow cylinder that is simply inserted into the top soil. An optimization method on the basis of objective of minimum error between the measured and simulated water depths in the single-ring is developed for determination of the soil hydraulic parameters. Using the single ring permeameter, we measured saturated hydraulic conductivities (Ks) of the red loam soil with and without vegetation covers on five hillslopes at Taoyuan Agro-Ecology Experimental Station, Hunan Province of China. For the measurement plots without vegetation roots, Ks value of the soil at 25cm depth is much smaller than that of surface soil (1.52×10-4 vs. 1.10×10-5 m/s). For the measurement plots with vegetation cover, plant roots significantly increase Ks of the lower layer soil but this increase is not significant for the shallow soil. Moreover, influences of vegetation root on Ks depend on vegetation species and ages. Ks value of the Camellia is about three times larger than that of seeding of Camphor (2.62×10-4 vs. 9.82×10-5 m/s). Ks value of the matured Camellia is 2.72×10-4 m/s while Ks value of the young Camellia is only 2.17×10-4 m/s. Key words: single ring permeameter; soil hydraulic conductivity; vegetation

12. Measurement of electrical conductivity for a biomass fire.

PubMed

Mphale, Kgakgamatso; Heron, Mal

2008-08-01

A controlled fire burner was constructed where various natural vegetation species could be used as fuel. The burner was equipped with thermocouples to measure fuel surface temperature and used as a cavity for microwaves with a laboratory quality 2-port vector network analyzer to determine electrical conductivity from S-parameters. Electrical conductivity for vegetation material flames is important for numerical prediction of flashover in high voltage power transmission faults research. Vegetation fires that burn under high voltage transmission lines reduce flashover voltage by increasing air electrical conductivity and temperature. Analyzer determined electrical conductivity ranged from 0.0058 - 0.0079 mho/m for a fire with a maximum temperature of 1240 K. PMID:19325812

13. Experiment of electrical conductivity at low temperature (preliminary measurement)

SciTech Connect

Zhao, Y.; Wang, H.

1998-07-01

A muon collider needs very large amount of RF power, how to reduce the RF power consumption is of major concern. Thus the application of liquid nitrogen cooling has been proposed. However, it is known that the electrical conductivity depends on many factors and the data from different sources vary in a wide range, especially the data of conductivity of beryllium has no demonstration in a real application. Therefore it is important to know the conductivity of materials, which are commercially available, and at a specified frequency. Here, the results of the preliminary measurement on the electrical conductivity of copper at liquid nitrogen temperature are summarized. Addressed also are the data fitting method and the linear expansion of copper.

14. Measurement of Electrical Conductivity for a Biomass Fire

PubMed Central

Mphale, Kgakgamatso; Heron, Mal

2008-01-01

A controlled fire burner was constructed where various natural vegetation species could be used as fuel. The burner was equipped with thermocouples to measure fuel surface temperature and used as a cavity for microwaves with a laboratory quality 2-port vector network analyzer to determine electrical conductivity from S-parameters. Electrical conductivity for vegetation material flames is important for numerical prediction of flashover in high voltage power transmission faults research. Vegetation fires that burn under high voltage transmission lines reduce flashover voltage by increasing air electrical conductivity and temperature. Analyzer determined electrical conductivity ranged from 0.0058 - 0.0079 mho/m for a fire with a maximum temperature of 1240 K. PMID:19325812

15. Measurements of prompt radiation induced conductivity of alumina and sapphire.

SciTech Connect

Hartman, E. Frederick; Zarick, Thomas Andrew; Sheridan, Timothy J.; Preston, Eric F.

2011-04-01

We performed measurements of the prompt radiation induced conductivity in thin samples of Alumina and Sapphire at the Little Mountain Medusa LINAC facility in Ogden, UT. Five mil thick samples were irradiated with pulses of 20 MeV electrons, yielding dose rates of 1E7 to 1E9 rad/s. We applied variable potentials up to 1 kV across the samples and measured the prompt conduction current. Analysis rendered prompt conductivity coefficients between 1E10 and 1E9 mho/m/(rad/s), depending on the dose rate and the pulse width for Alumina and 1E7 to 6E7 mho/m/(rad/s) for Sapphire.

16. Single-Crystal X-ray Structures of conductive π-Stacking Dimers of Tetrakis(alkylthio)benzene Radical Cations.

PubMed

Chen, Xiaoyu; Gao, Feng; Yang, Wuqin

2016-01-01

Salts containing radical cations of 1,2,4,5-tetrakis(isopropylthio)benzene (TPB) and 1,2,4,5-tetrakis(ethylthio) benzene (TEB) have been successfully synthesized with . These newly synthesized salts have been characterized by UV-Vis absorption, EPR spectroscopy, conductivity measurement, single crystal X-ray diffraction analysis as well as DFT calculation. This study raises the first crystal structure of conductive π-stacking radical cation with single phenyl ring and reveals their conductivity has relationship with the stack structure which affected by the substituent. PMID:27403720

17. Single-Crystal X-ray Structures of conductive π-Stacking Dimers of Tetrakis(alkylthio)benzene Radical Cations

PubMed Central

Chen, Xiaoyu; Gao, Feng; Yang, Wuqin

2016-01-01

Salts containing radical cations of 1,2,4,5-tetrakis(isopropylthio)benzene (TPB) and 1,2,4,5-tetrakis(ethylthio) benzene (TEB) have been successfully synthesized with . These newly synthesized salts have been characterized by UV-Vis absorption, EPR spectroscopy, conductivity measurement, single crystal X-ray diffraction analysis as well as DFT calculation. This study raises the first crystal structure of conductive π-stacking radical cation with single phenyl ring and reveals their conductivity has relationship with the stack structure which affected by the substituent. PMID:27403720

18. Single-Crystal X-ray Structures of conductive π-Stacking Dimers of Tetrakis(alkylthio)benzene Radical Cations

Chen, Xiaoyu; Gao, Feng; Yang, Wuqin

2016-07-01

Salts containing radical cations of 1,2,4,5-tetrakis(isopropylthio)benzene (TPB) and 1,2,4,5-tetrakis(ethylthio) benzene (TEB) have been successfully synthesized with . These newly synthesized salts have been characterized by UV-Vis absorption, EPR spectroscopy, conductivity measurement, single crystal X-ray diffraction analysis as well as DFT calculation. This study raises the first crystal structure of conductive π-stacking radical cation with single phenyl ring and reveals their conductivity has relationship with the stack structure which affected by the substituent.

19. Determining aerodynamic conductance of spar chambers from energy balance measurements

Technology Transfer Automated Retrieval System (TEKTRAN)

The aerodynamic conductance (gA) of SPAR chambers was determined from measurements of energy balance and canopy temperature over a peanut canopy. gA was calculated from the slope of sensible heat flux (H) versus canopy-to-air temperature difference. H and the canopy-to-air temperature were varied by...

20. Measuring Impulsivity in Adolescents with Serious Substance and Conduct Problems

ERIC Educational Resources Information Center

Thompson, Laetitia L.; Whitmore, Elizabeth A.; Raymond, Kristen M.; Crowley, Thomas J.

2006-01-01

Adolescents with substance use and conduct disorders have high rates of aggression and attention deficit hyperactivity disorder (ADHD), all of which have been characterized in part by impulsivity. Developing measures that capture impulsivity behaviorally and correlate with self-reported impulsivity has been difficult. One promising behavioral…

1. Apparatus measures thermal conductivity of honeycomb-core panels

NASA Technical Reports Server (NTRS)

1966-01-01

Overall thermal conductivity of honeycomb-core panels at elevated temperatures is measured by an apparatus with a heater assembly and a calibrated heat-rate transducer. The apparatus has space between the heater and transducer for insertion of a test panel and insulation.

2. Cosmic ray measurements around the knee

Chiavassa, Andrea

2016-07-01

Primary cosmic rays of energy greater than ˜ 1014 eV must be studied by indirect experiments measuring the particles generated in the EAS (Extensive Air Shower) development in atmosphere. These experiments are mainly limited by the systematic errors due to their energy calibration. I will discuss the main sources of these errors: the choice of the hadronic interaction model and of the mass of the primary particle (that cannot be measured on a event by event basis). I will then summarize some recent measurements of the all particle spectrum, and I will show that, keeping into account the differences due to the energy calibration, they all agree on the spectral shape. Then I will describe the measurements of the light and heavy primaries mass groups spectra, discussing the claimed features. Using a simple calculation of the elemental spectra (based on the hypothesis that the knee energies follow a Peter's cycle) I will try to discuss if all these results can be interpreted in a common picture.

3. Measuring the hydraulic conductivity of shallow submerged sediments.

PubMed

Kelly, Susan E; Murdoch, Lawrence C

2003-01-01

The hydraulic conductivity of submerged sediments influences the interaction between ground water and surface water, but few techniques for measuring K have been described with the conditions of the submerged setting in mind. Two simple, physical methods for measuring the hydraulic conductivity of submerged sediments have been developed, and one of them uses a well and piezometers similar to well tests performed in terrestrial aquifers. This test is based on a theoretical analysis that uses a constant-head boundary condition for the upper surface of the aquifer to represent the effects of the overlying water body. Existing analyses of tests used to measure the hydraulic conductivity of submerged sediments may contain errors from using the same upper boundary conditions applied to simulate terrestrial aquifers. Field implementation of the technique requires detecting minute drawdowns in the vicinity of the pumping well. Low-density oil was used in an inverted U-tube manometer to amplify the head differential so that it could be resolved in the field. Another technique was developed to measure the vertical hydraulic conductivity of sediments at the interface with overlying surface water. This technique uses the pan from a seepage meter with a piezometer fixed along its axis (a piezo-seep meter). Water is pumped from the pan and the head gradient is measured using the axial piezometer. Results from a sandy streambed indicate that both methods provide consistent and reasonable estimates of K. The pumping test allows skin effects to be considered, and the field data show that omitting the skin effect (e.g., by using a single well test) can produce results that underestimate the hydraulic conductivity of streambeds. PMID:12873006

4. Measuring Cosmological Parameters with Gamma Ray Bursts

Amati, Lorenzo; Della Valle, Massimo

2013-12-01

In a few dozen seconds, gamma ray bursts (GRBs) emit up to 1054 erg in terms of an equivalent isotropically radiated energy Eiso, so they can be observed up to z 10. Thus, these phenomena appear to be very promising tools to describe the expansion rate history of the universe. Here, we review the use of the Ep,i-Eiso correlation of GRBs to measure the cosmological density parameter ΩM. We show that the present data set of GRBs, coupled with the assumption that we live in a flat universe, can provide independent evidence, from other probes, that ΩM 0.3. We show that current (e.g. Swift, Fermi/GBM, Konus-WIND) and forthcoming gamma ray burst (GRB) experiments (e.g. CALET/GBM, SVOM, Lomonosov/UFFO, LOFT/WFM) will allow us to constrain ΩM with an accuracy comparable to that currently exhibited by Type Ia supernovae (SNe-Ia) and to study the properties of dark energy and their evolution with time.

5. Comparison of different methods for measuring thermal conductivities

SciTech Connect

Hartung, D.; Gather, F.; Klar, P. J.

2012-06-26

Two different methods for the measurement of the thermal conductivity have been applied to a glass (borosilicate) bulk sample. The first method was in the steady-state using an arrangement of gold wires on the sample to create a thermal gradient and to measure the temperatures locally. This allows one to calculate the in-plane thermal conductivity of the sample. The same wire arrangement was also used for a 3{omega}-measurement of the direction-independent bulk thermal conductivity. The 3{omega}-approach is based on periodical heating and a frequency dependent analysis of the temperature response. The results of both methods are in good agreement with each other for this isotropic material, if thermal and radiative losses are accounted for. Our results demonstrate that especially in the case of thin-film measurements, finite element analysis has to be applied to correct for heat losses due to geometry and radiation. In this fashion, the wire positions can be optimized in order to minimize measurement errors.

6. Thermal conductance measurement of windows: An innovative radiative method

SciTech Connect

Arpino, F.; Buonanno, G.; Giovinco, G.

2008-09-15

Heat transfer through window surfaces is one of the most important contributions to energy losses in buildings. Therefore, great efforts are made to design new window frames and glass assemblies with low thermal conductance. At the same time, it is also necessary to develop accurate measurement techniques in thermal characterisation of the above-mentioned building components. In this paper the authors show an innovative measurement method mainly based on radiative heat transfer (instead of the traditional convective one) which allows window thermal conductance measurements with corresponding uncertainty budget evaluation. The authors used the 3D finite volume software FLUENT {sup registered} to design the experimental apparatus. The numerical results have been employed for the system optimisation and metrological characterisation. (author)

7. Thermal Conductivity Measurement of Liquid-Quenched Higher Manganese Silicides

Nishino, Shunsuke; Miyata, Masanobu; Ohdaira, Keisuke; Koyano, Mikio; Takeuchi, Tsunehiro

2016-03-01

Higher manganese silicides (HMSs, MnSi γ , γ ˜ 1.75) show promise for use as low-cost and environmentally friendly thermoelectric materials. To reduce their thermal conductivity, we partially substituted the Mn site with heavy elements using liquid quenching. Fabricated samples possess a curly ribbon-shape with about a 10- μm thickness and 1-mm width, with high surface roughness. In this study, we determined the thermal conductivity of the curly-ribbon-shaped samples using two independent methods: the 3 ω method with two heat flow models, and the steady-state method using a physical property measurement system (PPMS; Quantum Design). We succeeded in estimating the thermal conductivity at the temperature range of 100-200 K using the PPMS. The estimated thermal conductivity of non-doped HMSs shows a constant value without temperature dependence of 2.2 ± 0.8 W K-1m-1 at 100-200 K. The difference of thermal conductivities of W-doped and non-doped HMSs was not recognized within the measurement error.

8. Device and method for measuring thermal conductivity of thin films

NASA Technical Reports Server (NTRS)

Amer, Tahani R. (Inventor); Subramanian, Chelakara (Inventor); Upchurch, Billy T. (Inventor); Alderfer, David W. (Inventor); Sealey, Bradley S. (Inventor); Burkett, Jr., Cecil G. (Inventor)

2001-01-01

A device and method are provided for measuring the thermal conductivity of rigid or flexible, homogeneous or heterogeneous, thin films between 50 .mu.m and 150 .mu.m thick with relative standard deviations of less than five percent. The specimen is sandwiched between like material, highly conductive upper and lower slabs. Each slab is instrumented with six thermocouples embedded within the slab and flush with their corresponding surfaces. A heat source heats the lower slab and a heat sink cools the upper slab. The heat sink also provides sufficient contact pressure onto the specimen. Testing is performed within a vacuum environment (bell-jar) between 10.sup.-3 to 10.sup.-6 Torr. An anti-radiant shield on the interior surface of the bell-jar is used to avoid radiation heat losses. Insulation is placed adjacent to the heat source and adjacent to the heat sink to prevent conduction losses. A temperature controlled water circulator circulates water from a constant temperature bath through the heat sink. Fourier's one-dimensional law of heat conduction is the governing equation. Data, including temperatures, are measured with a multi-channel data acquisition system. On-line computer processing is used for thermal conductivity calculations.

9. Error and uncertainty in Raman thermal conductivity measurements

SciTech Connect

Thomas Edwin Beechem; Yates, Luke; Graham, Samuel

2015-04-22

We investigated error and uncertainty in Raman thermal conductivity measurements via finite element based numerical simulation of two geometries often employed -- Joule-heating of a wire and laser-heating of a suspended wafer. Using this methodology, the accuracy and precision of the Raman-derived thermal conductivity are shown to depend on (1) assumptions within the analytical model used in the deduction of thermal conductivity, (2) uncertainty in the quantification of heat flux and temperature, and (3) the evolution of thermomechanical stress during testing. Apart from the influence of stress, errors of 5% coupled with uncertainties of ±15% are achievable for most materials under conditions typical of Raman thermometry experiments. Error can increase to >20%, however, for materials having highly temperature dependent thermal conductivities or, in some materials, when thermomechanical stress develops concurrent with the heating. A dimensionless parameter -- termed the Raman stress factor -- is derived to identify when stress effects will induce large levels of error. Together, the results compare the utility of Raman based conductivity measurements relative to more established techniques while at the same time identifying situations where its use is most efficacious.

10. Error and uncertainty in Raman thermal conductivity measurements

DOE PAGESBeta

Thomas Edwin Beechem; Yates, Luke; Graham, Samuel

2015-04-22

We investigated error and uncertainty in Raman thermal conductivity measurements via finite element based numerical simulation of two geometries often employed -- Joule-heating of a wire and laser-heating of a suspended wafer. Using this methodology, the accuracy and precision of the Raman-derived thermal conductivity are shown to depend on (1) assumptions within the analytical model used in the deduction of thermal conductivity, (2) uncertainty in the quantification of heat flux and temperature, and (3) the evolution of thermomechanical stress during testing. Apart from the influence of stress, errors of 5% coupled with uncertainties of ±15% are achievable for most materialsmore » under conditions typical of Raman thermometry experiments. Error can increase to >20%, however, for materials having highly temperature dependent thermal conductivities or, in some materials, when thermomechanical stress develops concurrent with the heating. A dimensionless parameter -- termed the Raman stress factor -- is derived to identify when stress effects will induce large levels of error. Together, the results compare the utility of Raman based conductivity measurements relative to more established techniques while at the same time identifying situations where its use is most efficacious.« less

11. X-ray ablation measurements and modeling for ICF applications

SciTech Connect

Anderson, A.T.

1996-09-01

X-ray ablation of material from the first wall and other components of an ICF (Inertial Confinement Fusion) chamber is a major threat to the laser final optics. Material condensing on these optics after a shot may cause damage with subsequent laser shots. To ensure the successful operation of the ICF facility, removal rates must be predicted accurately. The goal for this dissertation is to develop an experimentally validated x-ray response model, with particular application to the National Ignition Facility (NIF). Accurate knowledge of the x-ray and debris emissions from ICF targets is a critical first step in the process of predicting the performance of the target chamber system. A number of 1-D numerical simulations of NIF targets have been run to characterize target output in terms of energy, angular distribution, spectrum, and pulse shape. Scaling of output characteristics with variations of both target yield and hohlraum wall thickness are also described. Experiments have been conducted at the Nova laser on the effects of relevant x-ray fluences on various materials. The response was diagnosed using post-shot examinations of the surfaces with scanning electron microscope and atomic force microscope instruments. Judgments were made about the dominant removal mechanisms for each material. Measurements of removal depths were made to provide data for the modeling. The finite difference ablation code developed here (ABLATOR) combines the thermomechanical response of materials to x-rays with models of various removal mechanisms. The former aspect refers to energy deposition in such small characteristic depths ({approx} micron) that thermal conduction and hydrodynamic motion are significant effects on the nanosecond time scale. The material removal models use the resulting time histories of temperature and pressure-profiles, along with ancillary local conditions, to predict rates of surface vaporization and the onset of conditions that would lead to spallation.

12. Measurement of Fracture Geometry for Accurate Computation of Hydraulic Conductivity

Chae, B.; Ichikawa, Y.; Kim, Y.

2003-12-01

Fluid flow in rock mass is controlled by geometry of fractures which is mainly characterized by roughness, aperture and orientation. Fracture roughness and aperture was observed by a new confocal laser scanning microscope (CLSM; Olympus OLS1100). The wavelength of laser is 488nm, and the laser scanning is managed by a light polarization method using two galvano-meter scanner mirrors. The system improves resolution in the light axis (namely z) direction because of the confocal optics. The sampling is managed in a spacing 2.5 μ m along x and y directions. The highest measurement resolution of z direction is 0.05 μ m, which is the more accurate than other methods. For the roughness measurements, core specimens of coarse and fine grained granites were provided. Measurements were performed along three scan lines on each fracture surface. The measured data were represented as 2-D and 3-D digital images showing detailed features of roughness. Spectral analyses by the fast Fourier transform (FFT) were performed to characterize on the roughness data quantitatively and to identify influential frequency of roughness. The FFT results showed that components of low frequencies were dominant in the fracture roughness. This study also verifies that spectral analysis is a good approach to understand complicate characteristics of fracture roughness. For the aperture measurements, digital images of the aperture were acquired under applying five stages of uniaxial normal stresses. This method can characterize the response of aperture directly using the same specimen. Results of measurements show that reduction values of aperture are different at each part due to rough geometry of fracture walls. Laboratory permeability tests were also conducted to evaluate changes of hydraulic conductivities related to aperture variation due to different stress levels. The results showed non-uniform reduction of hydraulic conductivity under increase of the normal stress and different values of

13. Method of simultaneous measurement of radiative and lattice thermal conductivity.

NASA Technical Reports Server (NTRS)

Schatz, J. F.; Simmons, G.

1972-01-01

A new technique of high-temperature thermal-conductivity measurement is described. A CO2 gas laser is used to generate a low-frequency temperature wave at one face of a small disk-shaped sample, and an infrared detector views the opposite face to detect the phase of the emerging radiation. A mathematical expression is derived which enables phase data at several frequencies to be used for the simultaneous determination of thermal diffusivity and mean extinction coefficient. Lattice and radiative thermal conductivities are then calculated. Test results for sintered aluminum oxide at temperatures from 530 to 1924 K are within the range of error of previously existing data.

14. Assembly for electrical conductivity measurements in the piston cylinder device

DOEpatents

Watson, Heather Christine; Roberts, Jeffrey James

2012-06-05

An assembly apparatus for measurement of electrical conductivity or other properties of a sample in a piston cylinder device wherein pressure and heat are applied to the sample by the piston cylinder device. The assembly apparatus includes a body, a first electrode in the body, the first electrode operatively connected to the sample, a first electrical conductor connected to the first electrode, a washer constructed of a hard conducting material, the washer surrounding the first electrical conductor in the body, a second electrode in the body, the second electrode operatively connected to the sample, and a second electrical conductor connected to the second electrode.

15. Electrical conductivity measurements on silicate melts using the loop technique

NASA Technical Reports Server (NTRS)

Waff, H. S.

1976-01-01

A new method is described for measurement of the electrical conductivity of silicate melts under controlled oxygen partial pressure at temperatures to 1550 C. The melt samples are suspended as droplets on platinum-rhodium loops, minimizing iron loss from the melt due to alloying with platinum, and providing maximum surface exposure of the melt to the oxygen-buffering gas atmosphere. The latter provides extremely rapid equilibration of the melt with the imposed oxygen partial pressure. The loop technique involves a minimum of setup time and cost, provides reproducible results to within + or - 5% and is well suited to electrical conductivity studies on silicate melts containing redox cations.

16. System to Measure Thermal Conductivity and Seebeck Coefficient for Thermoelectrics

NASA Technical Reports Server (NTRS)

Kim, Hyun-Jung; Skuza, Jonathan R.; Park, Yeonjoon; King, Glen C.; Choi, Sang H.; Nagavalli, Anita

2012-01-01

The Seebeck coefficient, when combined with thermal and electrical conductivity, is an essential property measurement for evaluating the potential performance of novel thermoelectric materials. However, there is some question as to which measurement technique(s) provides the most accurate determination of the Seebeck coefficient at elevated temperatures. This has led to the implementation of nonstandardized practices that have further complicated the confirmation of reported high ZT materials. The major objective of the procedure described is for the simultaneous measurement of the Seebeck coefficient and thermal diffusivity within a given temperature range. These thermoelectric measurements must be precise, accurate, and reproducible to ensure meaningful interlaboratory comparison of data. The custom-built thermal characterization system described in this NASA-TM is specifically designed to measure the inplane thermal diffusivity, and the Seebeck coefficient for materials in the ranging from 73 K through 373 K.

17. Application of inverse heat conduction problem on temperature measurement

Zhang, X.; Zhou, G.; Dong, B.; Li, Q.; Liu, L. Q.

2013-09-01

For regenerative cooling devices, such as G-M refrigerator, pulse tube cooler or thermoacoustic cooler, the gas oscillating bring about temperature fluctuations inevitably, which is harmful in many applications requiring high stable temperatures. To find out the oscillating mechanism of the cooling temperature and improve the temperature stability of cooler, the inner temperature of the cold head has to be measured. However, it is difficult to measure the inner oscillating temperature of the cold head directly because the invasive temperature detectors may disturb the oscillating flow. Fortunately, the outer surface temperature of the cold head can be measured accurately by invasive temperature measurement techniques. In this paper, a mathematical model of inverse heat conduction problem is presented to identify the inner surface oscillating temperature of cold head according to the measured temperature of the outer surface in a GM cryocooler. Inverse heat conduction problem will be solved using control volume approach. Outer surface oscillating temperature could be used as input conditions of inverse problem and the inner surface oscillating temperature of cold head can be inversely obtained. A simple uncertainty analysis of the oscillating temperature measurement also will be provided.

18. Thermal conductivity measurements of particulate materials under Martian conditions

NASA Technical Reports Server (NTRS)

Presley, M. A.; Christensen, P. R.

1993-01-01

The mean particle diameter of surficial units on Mars has been approximated by applying thermal inertia determinations from the Mariner 9 Infrared Radiometer and the Viking Infrared Thermal Mapper data together with thermal conductivity measurement. Several studies have used this approximation to characterize surficial units and infer their nature and possible origin. Such interpretations are possible because previous measurements of the thermal conductivity of particulate materials have shown that particle size significantly affects thermal conductivity under martian atmospheric pressures. The transfer of thermal energy due to collisions of gas molecules is the predominant mechanism of thermal conductivity in porous systems for gas pressures above about 0.01 torr. At martian atmospheric pressures the mean free path of the gas molecules becomes greater than the effective distance over which conduction takes place between the particles. Gas particles are then more likely to collide with the solid particles than they are with each other. The average heat transfer distance between particles, which is related to particle size, shape and packing, thus determines how fast heat will flow through a particulate material.The derived one-to-one correspondence of thermal inertia to mean particle diameter implies a certain homogeneity in the materials analyzed. Yet the samples used were often characterized by fairly wide ranges of particle sizes with little information about the possible distribution of sizes within those ranges. Interpretation of thermal inertia data is further limited by the lack of data on other effects on the interparticle spacing relative to particle size, such as particle shape, bimodal or polymodal mixtures of grain sizes and formation of salt cements between grains. To address these limitations and to provide a more comprehensive set of thermal conductivities vs. particle size a linear heat source apparatus, similar to that of Cremers, was assembled to

19. X-ray absorption and reflection as probes of the GaN conduction bands: Theory and experiments

SciTech Connect

Lambrecht, W.R.L.; Rashkeev, S.N.; Segall, B.

1997-04-01

X-ray absorption measurements are a well-known probe of the unoccupied states in a material. The same information can be obtained by using glancing angle X-ray reflectivity. In spite of several existing band structure calculations of the group III nitrides and previous optical studies in UV range, a direct probe of their conduction band densities of states is of interest. The authors performed a joint experimental and theoretical investigation using both of these experimental techniques for wurtzite GaN.

20. Characterization of uranium bearing material using x-ray fluorescence and direct gamma-rays measurement techniques

Mujaini, M.; Chankow, N.; Yusoff, M. Z.; Hamid, N. A.

2016-01-01

Uranium ore can be easily detected due to various gamma-ray energies emitted from uranium daughters particularly from 238U daughters such as 214Bi, 214Pb and 226Ra. After uranium is extracted from uranium ore, only low energy gamma-rays emitted from 235U may be detected if the detector is placed in close contact to the specimen. In this research, identification and characterization of uranium bearing materials is experimentally investigated using direct measurement of gamma-rays from 235U in combination with the x-ray fluorescence (XRF) technique. Measurement of gamma-rays can be conducted by using high purity germanium (HPGe) detector or cadmium telluride (CdTe) detector while a 57Coradioisotope-excited XRF spectrometer using CdTe detector is used for elemental analysis. The proposed technique was tested with various uranium bearing specimens containing natural, depleted and enriched uranium in both metallic and powder forms.

1. Thermal Conductivity Based on Modified Laser Flash Measurement

NASA Technical Reports Server (NTRS)

Lin, Bochuan; Ban, Heng; Li, Chao; Scripa, Rosalia N.; Su, Ching-Hua; Lehoczky, Sandor L.

2005-01-01

The laser flash method is a standard method for thermal diffusivity measurement. It employs single-pulse heating of one side of a thin specimen and measures the temperature response of the other side. The thermal diffusivity of the specimen can be obtained based on a one-dimensional transient heat transfer analysis. This paper reports the development of a theory that includes a transparent reference layer with known thermal property attached to the back of sample. With the inclusion of heat conduction from the sample to the reference layer in the theoretical analysis, the thermal conductivity and thermal diffusivity of sample can be extracted from the temperature response data. Furthermore, a procedure is established to select two points from the data to calculate these properties. The uncertainty analysis indicates that this method can be used with acceptable levels of uncertainty.

2. Investigating the Defect Structures in Transparent Conducting Oxides Using X-ray and Neutron Scattering Techniques

SciTech Connect

González, Gabriela B.

2012-10-23

Transparent conducting oxide (TCO) materials are implemented into a wide variety of commercial devices because they possess a unique combination of high optical transparency and high electrical conductivity. Created during the processing of the TCOs, defects within the atomic-scale structure are responsible for their desirable optical and electrical properties. Therefore, studying the defect structure is essential to a better understanding of the behavior of transparent conductors. X-ray and neutron scattering techniques are powerful tools to investigate the atomic lattice structural defects in these materials. This review paper presents some of the current developments in the study of structural defects in n-type TCOs using x-ray diffraction (XRD), neutron diffraction, extended x-ray absorption fine structure (EXAFS), pair distribution functions (PDFs), and x-ray fluorescence (XRF).

3. Optoelectronic measurement of x-ray synchrotron pulses: A proof of concept demonstration

SciTech Connect

Durbin, Stephen M.; Caffee, Marc; Savikhin, Sergei; Mahmood, Aamer; Dufresne, Eric M.; Wen, Haidan; Li, Yuelin

2013-02-04

Optoelectronic detection using photoconductive coplanar stripline devices has been applied to measuring the time profile of x-ray synchrotron pulses, a proof of concept demonstration that may lead to improved time-resolved x-ray studies. Laser sampling of current vs time delay between 12 keV x-ray and 800 nm laser pulses reveal the {approx}50 ps x-ray pulse width convoluted with the {approx}200 ps lifetime of the conduction band carriers. For GaAs implanted with 8 MeV protons, a time profile closer to the x-ray pulse width is observed. The protons create defects over the entire depth sampled by the x-rays, trapping the x-ray excited conduction electrons and minimizing lifetime broadening of the electrical excitation.

4. Measurement of cosmic rays with LOFAR

Rossetto, L.; Buitink, S.; Corstanje, A.; Enriquez, J. E.; Falcke, H.; Hörandel, J. R.; Nelles, A.; Rachen, J. P.; Schellart, P.; Scholten, O.; ter Veen, S.; Thoudam, S.; Trinh, T. N. G.

2016-05-01

5. Heating rate controller for thermally stimulated conductivity and thermoluminescence measurements.

NASA Technical Reports Server (NTRS)

Manning, E. G.; Littlejohn, M. A.; Oakley, E. M.; Hutchby , J. A.

1972-01-01

A temperature controller is described which enables the temperature of a sample mounted on a cold finger to be varied linearly with time. Heating rates between 0.5 and 10 K/min can be achieved for temperatures between 90 and 300 K. Provision for terminating the sample heating at any temperature between these extremes is available. The temperature can be held at the terminating temperature or be reduced to the starting temperature in a matter of minutes. The controller has been used for thermally stimulated conductivity measurements and should be useful for thermoluminescence measurements as well.

6. The role of probe oxide in local surface conductivity measurements

SciTech Connect

Barnett, C. J.; Kryvchenkova, O.; Wilson, L. S. J.; Maffeis, T. G. G.; Cobley, R. J.; Kalna, K.

2015-05-07

Local probe methods can be used to measure nanoscale surface conductivity, but some techniques including nanoscale four point probe rely on at least two of the probes forming the same low resistivity non-rectifying contact to the sample. Here, the role of probe shank oxide has been examined by carrying out contact and non-contact I V measurements on GaAs when the probe oxide has been controllably reduced, both experimentally and in simulation. In contact, the barrier height is pinned but the barrier shape changes with probe shank oxide dimensions. In non-contact measurements, the oxide modifies the electrostatic interaction inducing a quantum dot that alters the tunneling behavior. For both, the contact resistance change is dependent on polarity, which violates the assumption required for four point probe to remove probe contact resistance from the measured conductivity. This has implications for all nanoscale surface probe measurements and macroscopic four point probe, both in air and vacuum, where the role of probe oxide contamination is not well understood.

7. Rise Time Measurement for Ultrafast X-Ray Pulses

DOEpatents

Celliers, Peter M.; Weber, Franz A.; Moon, Stephen J.

2005-04-05

A pump-probe scheme measures the rise time of ultrafast x-ray pulses. Conventional high speed x-ray diagnostics (x-ray streak cameras, PIN diodes, diamond PCD devices) do not provide sufficient time resolution to resolve rise times of x-ray pulses on the order of 50 fs or less as they are being produced by modern fast x-ray sources. Here, we are describing a pump-probe technique that can be employed to measure events where detector resolution is insufficient to resolve the event. The scheme utilizes a diamond plate as an x-ray transducer and a p-polarized probe beam.

8. Rise time measurement for ultrafast X-ray pulses

DOEpatents

Celliers, Peter M.; Weber, Franz A.; Moon, Stephen J.

2005-04-05

A pump-probe scheme measures the rise time of ultrafast x-ray pulses. Conventional high speed x-ray diagnostics (x-ray streak cameras, PIN diodes, diamond PCD devices) do not provide sufficient time resolution to resolve rise times of x-ray pulses on the order of 50 fs or less as they are being produced by modern fast x-ray sources. Here, we are describing a pump-probe technique that can be employed to measure events where detector resolution is insufficient to resolve the event. The scheme utilizes a diamond plate as an x-ray transducer and a p-polarized probe beam.

9. TRISO fuel compact thermal conductivity measurement instrument development

Jensen, Colby

Thermal conductivity is an important thermophysical property needed for effectively predicting fuel performance. As part of the Next Generation Nuclear Plant (NGNP) program, the thermal conductivity of tri-isotropic (TRISO) fuel needs to be measured over a temperature range characteristic of its usage. The composite nature of TRISO fuel requires that measurement be performed over the entire length of the compact in a non-destructive manner. No existing measurement system is capable of performing such a measurement. A measurement system has been designed based on the steady-state, guarded-comparative-longitudinal heat flow technique. The system as currently designed is capable of measuring cylindrical samples with diameters ˜12.3-mm (˜0.5″) with lengths ˜25-mm (˜1″). The system is currently operable in a temperature range of 400 K to 1100 K for materials with thermal conductivities on the order of 10 W/m/K to 70 W/m/K. The system has been designed, built, and tested. An uncertainty analysis for the determinate errors of the system has been performed finding a result of 5.5%. Finite element modeling of the system measurement method has also been accomplished demonstrating optimal design, operating conditions, and associated bias error. Measurements have been performed on three calibration/validation materials: SS304, 99.95% pure iron, and inconel 625. In addition, NGNP graphite with ZrO2 particles and NGNP AGR-2 graphite matrix only, both in compact form, have been measured. Results from the SS304 sample show agreement of better than 3% for a 300--600°C temperature range. For iron between 100--600°C, the difference with published values is <8% for all temperatures. The maximum difference from published data for inconel 625 is 5.8%, near 600°C. Both NGNP samples were measured from 100--800°C. All results are presented and discussed. Finally, a discussion of ongoing work is included as well as a brief discussion of implementation under other operating

10. Measurements Conducted on an Unknown Object Labeled Pu-239

SciTech Connect

Hoteling, Nathan

2013-11-18

Measurements were carried out on 12 November 2013 to determine whether Pu-239 was present on an object discovered in a plastic bag with label “Pu-­239 6 uCi.” Following initial survey measurements to verify that the object was not leaking or contaminated, spectra were collected with a High Purity Germanium (HPGe) detector with object positioned in two different configurations. Analysis of the spectra did not yield any direct evidence of Pu-­239. From the measured spectra, minimum detectable activity (MDA) was determined to be approximately 2 uCi for the gamma-­ray measurements. Although there was no direct evidence of Pu-239, a peak at 60 keV characteristic of Am-­241 decay was observed. Since it is very likely that Am-­241 would be present in aged plutonium samples, this was interpreted as indirect evidence for the presence of plutonium on the object. Analysis of this peak led to an estimated Pu-­239 activity of 0.02–0.04 uCi, or <1x10-6 grams.

11. Silicate bonding properties: Investigation through thermal conductivity measurements

Lorenzini, M.; Cesarini, E.; Cagnoli, G.; Campagna, E.; Haughian, K.; Hough, J.; Losurdo, G.; Martelli, F.; Martin, I.; Piergiovanni, F.; Reid, S.; Rowan, S.; van Veggel, A. A.; Vetrano, F.

2010-05-01

A direct approach to reduce the thermal noise contribution to the sensitivity limit of a GW interferometric detector is the cryogenic cooling of the mirrors and mirrors suspensions. Future generations of detectors are foreseen to implement this solution. Silicon has been proposed as a candidate material, thanks to its very low intrinsic loss angle at low temperatures and due to its very high thermal conductivity, allowing the heat deposited in the mirrors by high power lasers to be efficiently extracted. To accomplish such a scheme, both mirror masses and suspension elements must be made of silicon, then bonded together forming a quasi-monolithic stage. Elements can be assembled using hydroxide-catalysis silicate bonding, as for silica monolithic joints. The effect of Si to Si bonding on suspension thermal conductance has therefore to be experimentally studied. A measurement of the effect of silicate bonding on thermal conductance carried out on 1 inch thick silicon bonded samples, from room temperature down to 77 K, is reported. In the explored temperature range, the silicate bonding does not seem to affect in a relevant way the sample conductance.

12. Accelerated life ac conductivity measurements of CRT oxide cathodes

Hashim, A. A.; Barratt, D. S.; Hassan, A. K.; Nabok, A.

2006-07-01

The ac conductivity measurements have been carried out for the activated Ba/SrO cathode with additional 5% Ni powder for every 100 h acceleration life time at the temperature around 1125 K. The ac conductivity was studied as a function of temperature in the range 300-1200 K after conversion and activation of the cathode at 1200 K for 1 h in two cathodes face to face closed configuration. The experimental results prove that the hopping conductivity dominate in the temperature range 625-770 K through the traps of the WO 3 associate with activation energy Ea = 0.87 eV, whereas from 500-625 K it is most likely to be through the traps of the Al 2O 3 with activation energy of Ea = 1.05 eV. The hopping conductivity at the low temperature range 300-500 K is based on Ni powder link with some Ba contaminants in the oxide layer stricture which indicates very low activation energy Ea = 0.06 eV.

13. Analysis of measurements of the thermal conductivity of liquid urania

SciTech Connect

Fink, J.K.; Leibowitz, L.

1984-09-17

An analysis was performed of the three existing measurements of the thermal conductivity and thermal diffusivity of molten uranium dioxide. A transient heat transfer code (THTB) was used for this analysis. A much smaller range of values for thermal conductivity than originally reported was found: the original values ranged from 2.4 to 11 W . m/sup -1/ . K/sup -1/, with a mean of 7.3 W . m/sup -1/ . K/sup -1/, whereas the recalculated values ranged from 4.5 to 6.75 W . m/sup -1/ . K/sup -1/, with a mean of 5.6 W . m/sup -1/ . K/sup -1/.

14. Thermal conductivity measurements in a 2D Yukawa system

Nosenko, V.; Ivlev, A.; Zhdanov, S.; Morfill, G.; Goree, J.; Piel, A.

2007-03-01

Thermal conductivity was measured for a 2D Yukawa system. First, we formed a monolayer suspension of microspheres in a plasma, i.e., a dusty plasma, which is like a colloidal suspension, but with an extremely low volume fraction and a partially-ionized rarefied gas instead of solvent. In the absence of manipulation, the suspension forms a 2D triangular lattice. To melt this lattice and form a liquid, we used a laser-heating method. Two focused laser beams were moved rapidly around in the monolayer. The kinetic temperature of the particles increased with the laser power applied, and above a threshold a melting transition occurred. We used digital video microscopy for direct imaging and particle tracking. The spatial profiles of the particle kinetic temperature were calculated. Using the heat transport equation with an additional term to account for the energy dissipation due to the gas drag, we analyzed the temperature distribution to derive the thermal conductivity.

15. Thermal conductivity and emissivity measurements of uranium carbides

Corradetti, S.; Manzolaro, M.; Andrighetto, A.; Zanonato, P.; Tusseau-Nenez, S.

2015-10-01

Thermal conductivity and emissivity measurements on different types of uranium carbide are presented, in the context of the ActiLab Work Package in ENSAR, a project within the 7th Framework Program of the European Commission. Two specific techniques were used to carry out the measurements, both taking place in a laboratory dedicated to the research and development of materials for the SPES (Selective Production of Exotic Species) target. In the case of thermal conductivity, estimation of the dependence of this property on temperature was obtained using the inverse parameter estimation method, taking as a reference temperature and emissivity measurements. Emissivity at different temperatures was obtained for several types of uranium carbide using a dual frequency infrared pyrometer. Differences between the analyzed materials are discussed according to their compositional and microstructural properties. The obtainment of this type of information can help to carefully design materials to be capable of working under extreme conditions in next-generation ISOL (Isotope Separation On-Line) facilities for the generation of radioactive ion beams.

16. Bone mineral measurement using dual energy x ray densitometry

NASA Technical Reports Server (NTRS)

Smith, Steven W.

1989-01-01

Bone mineral measurements before and after space missions have shown that weightlessness greatly accelerates bone demineralization. Bone mineral losses as high as 1 to 3 percent per month were reported. Highly precise instrumentation is required to monitor this loss and thereby test the efficacy of treatment. During the last year, a significant improvement was made in Dual-Photon Absorptiometry by replacing the radioactive source with an x ray tube. Advantages of this system include: better precision, lower patient dose, better spacial resolution, and shorter scan times. The high precision and low radiation dose of this technique will allow detection of bone mineral changes of less than 1 percent with measurements conducted directly at the sites of interest. This will allow the required bone mineral studies to be completed in a shorter time with greater confidence.

17. The unsaturated hydraulic conductivity: measurement and non-equilibrium effects

Weller, U.; Vogel, H.

2010-12-01

The unsaturated hydraulic conductivity of porous media is a central item in hydraulic modeling. It is hard to measure and therefore in most applications it is represented by some kind of model based on indirect measurements. The validity is hardly ever checked. We have developed a fairly easy and automatic measurement procedure that allows to determine directly the hydraulic conductivity of a sample at different water potentials. The sample is placed on a plate where the potential can be controlled. It is then irrigated from the top with a constant, predefined flow rate. Tensiometers control the water potential within the sample, the topmost one is used to steer the potential at the lower boundary. It can be seen that the sample equilibrates fairly quick to a constant potential throughout the sample, and thus the conductivity of the material at the measured potential is equal to the applied flux while gravity is the only driving force. The change in water content is monitored by a balance. We have measured several materials, soils and sand substrates, with a protocol where we first lower the flux stepwise and then rise it again. The samples reach quick an equilibrium, as can be seen by the control tensiometer. Coming from the wet side, with a high flux, and lowering this flux, we observe a fast drop in potential, and in water content. But then the water potential rises again, while the water content remains constant or drops even slightly. When rising the flux again, we observe the opposite effect, but less pronounced: after the initial rise in water potential while the system adapts to the new flow rate, the potential lowers slightly. This behavior occurs over a certain range of water potential, it is not present in the very wet or very dry range. Also, the range in which it occurs and the magnitude of the effect depends on the studied material: pure sands express the pattern very clearly, it is much less obvious in loamy soils. Also, the relation between water

18. Experimental measurements of the thermal conductivity of ash deposits: Part 1. Measurement technique

SciTech Connect

A. L. Robinson; S. G. Buckley; N. Yang; L. L. Baxter

2000-04-01

This paper describes a technique developed to make in situ, time-resolved measurements of the effective thermal conductivity of ash deposits formed under conditions that closely replicate those found in the convective pass of a commercial boiler. Since ash deposit thermal conductivity is thought to be strongly dependent on deposit microstructure, the technique is designed to minimize the disturbance of the natural deposit microstructure. Traditional techniques for measuring deposit thermal conductivity generally do not preserve the sample microstructure. Experiments are described that demonstrate the technique, quantify experimental uncertainty, and determine the thermal conductivity of highly porous, unsintered deposits. The average measured conductivity of loose, unsintered deposits is 0.14 {+-} 0.03 W/(m K), approximately midway between rational theoretical limits for deposit thermal conductivity.

19. Apparent thermal conductivity measurements by an unguarded technique

Graves, R. S.; Yarbrough, D. W.; McElroy, D. L.

An unguarded longitudinal heat flow apparatus for measuring the apparent thermal conductivity (lambda/sub a) of insulations was tested. Heat flow is provided by a horizontal electrically heated Nichrome screen sandwiched between test samples that are bounded by temperature controlled copper plates and 9 cm of mineral fiber insulation. A determinate error analysis shows lambda/sub a/ measurement uncertainty to be less than + or - 1.7% for insulating materials as thin as 3 cm. Three-dimensional thermal modeling indicates negligible error in lambda/sub a/ due to edge loss for insulations up to 7.62 cm thick when the temperature difference across the sample is measured at the screen center. System repeatability and reproducibility were determined to be + or - 0.2%. Differences of lambda/sub a/ results from the screen tester and results from the National Bureau of Standards were 0.1% for a 10-kg/m(3) Calibration Transfer Standard and 0.9% for 127-kg/m(3) fibrous glass board (SRM 1450b). Measurements on fiberglass and rock wool batt insulations showed the dependence of lambda/sub a/ on density, temperature, temperature difference, plate emittance, and heat flow direction. Results obtained for lambda/sub a/ as a function of density at 240C differed by less than 2% from values obtained with a guarded hot plate. It is demonstrated that this simple technique has the accuracy and sensitivity needed for useful lambda/sub a/ measurements on thermal insulating materials.

20. Synthesis, conductivity, and X-ray photoelectron spectrum of Bi 2Sr 2CuO 7+X. A new ternary bismuth-oxide system exhibiting metallic conductivity

Porter, Leigh Christopher; Appelman, Evan; Beno, Mark A.; Cariss, Carolyn S.; Carlson, K. Douglas; Cohen, Harry; Geiser, Urs; Thorn, R. J.; Williams, Jack M.

1988-06-01

The preparation and some of the properties relating to the superconductive state of the newly discovered ternary bismuth oxide, Bi 2Sr 2Cu 2O 7+x, are described. Conductivity behavior ranging from semiconductive to metallic is observed when four-probe AC resistivity measurements are carried out on pressed pellet specimens that have been annealed under different conditions. From a determination of the total oxygen present by an iodometric titration, it was found that metallic conductivity was associated with a higher oxygen content. An X-ray photoelectron experiment was carried out in order to determine whether bismuth or copper was present as the mixed-valent species. The XPS spectrum of the Bi 4 f orbital electrons in the oxide was nearly identical to that observed in Bi 2O 3, with no evidence of any Bi 5+.

1. Synthesis conductivity, and x ray photoelectron spectrum of Bi2Sr2Cu(sub 7+x). A new ternary bismuth-oxide system exhibiting metallic conductivity

Porter, Leigh Christopher; Appleman, Evan; Beno, Mark A.; Cariss, Carolyn S.; Carlson, K. Douglas; Cohen, Harry; Geiser, Urs; Thorn, R. J.; Williams, John M.

The preparation and some of the properties relating to the superconductive state of the newly discovered ternary bismuth oxides, Bi2Sr2Cu2O(7+x), are described. Conductivity behavior ranging from semiconductive to metallic is observed when four-probe ac resistivity measurements are carried out on pressed pellet specimens that have been annealed under different conditions. From a determination of the total oxygen present by an iodometric titration, it was found that metallic conductivity was associated with a higher oxygen content. An x ray photoelectron experiment was carried out in order to determine whether bismuth or copper was present as the mixed valent species. The XPS spectrum of the Bi 4f orbital electrons in the oxides was nearly identical to that observed in Bi2O3, with no evidence of any Bi5(+).

2. Iron and cadmium capture gamma-ray photofission measurements

SciTech Connect

Williamson, T.G. . Dept. of Nuclear Engineering); Lamaze, G.P.; Gilliam, D.M.; Eisenhauer, C.M. )

1990-01-01

Photofission measurements have been made in {sup 238}U, {sup 232}Th, and {sup 237}Np in iron and cadmium capture gamma-ray spectra in cylindrical neutron-driven gamma-ray sources in the thermal column of the National Bureau of Standards (NBS) Reactor. The gamma-ray source strength was measured with neutron activation foils and by direct counting of activations produced in the metal cylinders. Photofission measurements were made with NBS miniature fission chambers. The integral photofission cross sections were compared with differential measurements by integrating the capture gamma-ray spectra with measured cross-section shapes. The integral cross sections measured in the capture gamma-ray fields are lower than the cross sections calculated from measured differential data.

3. Quantitative measurements of root water uptake and root hydraulic conductivities

Zarebanadkouki, Mohsen; Javaux, Mathieu; Meunier, Felicien; Couvreur, Valentin; Carminati, Andrea

2016-04-01

How is root water uptake distributed along the root system and what root properties control this distribution? Here we present a method to: 1) measure root water uptake and 2) inversely estimate the root hydraulic conductivities. The experimental method consists in using neutron radiography to trace deuterated water (D2O) in soil and roots. The method was applied to lupines grown aluminium containers filled with a sandy soil. When the lupines were 4 weeks old, D2O was locally injected in a selected soil regions and its transport was monitored in soil and roots using time-series neutron radiography. By image processing, we quantified the concentration of D2O in soil and roots. We simulated the transport of D2O into roots using a diffusion-convection numerical model. The diffusivity of the roots tissue was inversely estimated by simulating the transport of D2O into the roots during night. The convective fluxes (i.e. root water uptake) were inversely estimating by fitting the experiments during day, when plants were transpiring, and assuming that root diffusivity did not change. The results showed that root water uptake was not uniform along the roots. Water uptake was higher at the proximal parts of the lateral roots and it decreased by a factor of 10 towards the distal parts. We used the data of water fluxes to inversely estimate the profile of hydraulic conductivities along the roots of transpiring plants growing in soil. The water fluxes in the lupine roots were simulated using the Hydraulic Tree Model by Doussan et al. (1998). The fitting parameters to be adjusted were the radial and axial hydraulic conductivities of the roots. The results showed that by using the root architectural model of Doussan et al. (1998) and detailed information of water fluxes into different root segments we could estimate the profile of hydraulic conductivities along the roots. We also found that: 1) in a tap-rooted plant like lupine water is mostly taken up by lateral roots; (2) water

4. High-energy x-ray backlighter spectrum measurements using calibrated image plates

SciTech Connect

Maddox, B.R.; Park, H.S.; Remington, B.A.; Izumi, N.; Chen, S.; Chen, C.; Kimminau, G.; Ali, Z.; Haugh, M.J.; Ma, Q.

2012-10-10

The x-ray spectrum between 18 and 88 keV generated by a petawatt laser driven x-ray backlighter target was measured using a 12-channel differential filter pair spectrometer. The spectrometer consists of a series of filter pairs on a Ta mask coupled with an x-ray sensitive image plate. A calibration of Fuji{trademark} MS and SR image plates was conducted using a tungsten anode x-ray source and the resulting calibration applied to the design of the Ross pair spectrometer. Additionally, the fade rate and resolution of the image plate system were measured for quantitative radiographic applications. The conversion efficiency of laser energy into silver K{alpha} x rays from a petawatt laser target was measured using the differential filter pair spectrometer and compared to measurements using a single photon counting charge coupled device.

5. Fabrication, characterization and measurement of thermal conductivity of Fe 3O 4 nanofluids

2010-12-01

Magnetite Fe 3O 4 nanoparticles were synthesized by a co-precipitation method at different pH values. The products were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electronic microscopy. Their magnetic properties were evaluated on a vibrating sample magnetometer. The results show that the shape of the particles is cubic and they are superparamagnetic at room temperature. Magnetic nanofluids were prepared by dispersing the Fe 3O 4 nanoparticles in water as a base fluid in the presence of tetramethyl ammonium hydroxide as a dispersant. The thermal conductivity of the nanofluids was measured as a function of volume fraction and temperature. The results show that the thermal conductivity ratio of the nanofluids increases with increase in temperature and volume fraction. The highest enhancement of thermal conductivity was 11.5% in the nanofluid of 3 vol% of nanoparticles at 40 °C. The experimental results were also compared with the theoretical models.

6. Cosmic Rays: studies and measurements before 1912

De Angelis, Alessandro

2013-06-01

The discovery of cosmic rays, a milestone in science, was based on the work by scientists in Europe and the New World and took place during a period characterised by nationalism and lack of communication. Many scientists that took part in this research a century ago were intrigued by the penetrating radiation and tried to understand the origin of it. Several important contributions to the discovery of the origin of cosmic rays have been forgotten; historical, political and personal facts might have contributed to their substantial disappearance from the history of science.

7. Course Manual for X-Ray Measurements.

ERIC Educational Resources Information Center

This is the second of a series of three instructor manuals in x-ray science and engineering and is produced as part of a project of Oregon State University's Bureau of Radiological Health. This manual, and the two campanion manuals, have been tested in courses at Oregon State. These materials have been designed to serve as models for teaching and…

8. Electrical conductivity measurements of bacterial nanowires from Pseudomonas aeruginosa

Maruthupandy, Muthusamy; Anand, Muthusamy; Maduraiveeran, Govindhan; Sait Hameedha Beevi, Akbar; Jeeva Priya, Radhakrishnan

2015-12-01

The extracellular appendages of bacteria (flagella) that transfer electrons to electrodes are called bacterial nanowires. This study focuses on the isolation and separation of nanowires that are attached via Pseudomonas aeruginosa bacterial culture. The size and roughness of separated nanowires were measured using transmission electron microscopy (TEM) and atomic force microscopy (AFM), respectively. The obtained bacterial nanowires indicated a clear image of bacterial nanowires measuring 16 nm in diameter. The formation of bacterial nanowires was confirmed by microscopic studies (AFM and TEM) and the conductivity nature of bacterial nanowire was investigated by electrochemical techniques. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), which are nondestructive voltammetry techniques, suggest that bacterial nanowires could be the source of electrons—which may be used in various applications, for example, microbial fuel cells, biosensors, organic solar cells, and bioelectronic devices. Routine analysis of electron transfer between bacterial nanowires and the electrode was performed, providing insight into the extracellular electron transfer (EET) to the electrode. CV revealed the catalytic electron transferability of bacterial nanowires and electrodes and showed excellent redox activities. CV and EIS studies showed that bacterial nanowires can charge the surface by producing and storing sufficient electrons, behave as a capacitor, and have features consistent with EET. Finally, electrochemical studies confirmed the development of bacterial nanowires with EET. This study suggests that bacterial nanowires can be used to fabricate biomolecular sensors and nanoelectronic devices.

9. Scanning Ion Conductance Microscopy for living cell membrane potential measurement

Panday, Namuna

Recently, the existence of multiple micro-domains of extracellular potential around individual cells have been revealed by voltage reporter dye using fluorescence microscopy. One hypothesis is that these long lasting potential patterns play a vital role in regulating important cell activities such as embryonic patterning, regenerative repair and reduction of cancerous disorganization. We used multifunctional Scanning Ion Conductance Microscopy (SICM) to study these extracellular potential patterns of single cell with higher spatial resolution. To validate this novel technique, we compared the extracellular potential distribution on the fixed HeLa cell surface and Polydimethylsiloxane (PDMS) surface and found significant difference. We then measured the extracellular potential distributions of living melanocytes and melanoma cells and found both the mean magnitude and spatial variation of extracellular potential of the melanoma cells are bigger than those of melanocytes. As compared to the voltage reporter dye based fluorescence microscope method, SICM can achieve quantitative potential measurements of non-labeled living cell membranes with higher spatial resolution.

10. Geodesic constant method: A novel approach to analytical surface-ray tracing on convex conducting bodies

Jha, R. M.; Wiesbeck, W.

1995-04-01

A generalized approach to analytical surface-ray tracing in three dimensions, and a review of its application to convex conducting bodies, is presented, using the Eisenhart Coordinate System. The ray-parameters so obtained, for quadric cylinders (QUACYLs) and surfaces of revolution (QUASORs), are in a one-parameter form for UTD mutual-coupling applications. The ray analysis is also extended to the hybrid QUACYLs (e.g., aircraft wings) and hybrid QUASORs (e.g., satellite-launch vehicles), by introducing Hertz's principle of particle dynamics to EM theory. This mathematical formulation is applicable even to other important non-Eisenhart surfaces, such as the ogive. A summary of the mathematical formulations is included.

11. Inelastic cross sections from gamma-ray measurements

SciTech Connect

Nelson, Ronald Owen

2010-12-06

Measurements of gamma rays following neutron induced reactions have been studied with the Germanium Array for Neutron-induced Excitations (GEANIE) at the Los Alamos Neutron Science Center (LANSCE) for many years. Gamma-ray excitation functions and coincidence studies provide insight into nuclear reaction mechanisms as well as expanding our knowledge of energy levels and gamma-rays. Samples studied with Ge detectors at LANSCE range from Be to Pu. Fe, Cr and Ti have been considered for use as reference cross sections. An overview of the measurements and efforts to create a reliable neutron-induced gamma-ray reference cross section will be presented.

12. ICF burn-history measurments using 17-MeV fusion gamma rays

SciTech Connect

Lerche, R.A.; Cable, M.D.; Dendooven, P.G.

1995-04-12

Fusion reaction rate for inertial-confinement fusion (ICF) experiments at the Nova Laser Facility is measured with 30-ps resolution using a high-speed neutron detector. We are investigating a measurement technique based on the 16.7-MeV gamma rays that are released in deuterium-tritium fusion. Our concept is to convert gamma-ray energy into a fast burst of Cerenkov light that can be recorded with a high-speed optical detector. We have detected fusion gamma rays in preliminary experiments conducted at Nova where we used a tungsten/aerogel converter to generate Cerenkov light and an optical streak camera to record the signal.

13. Thermal contact conductance measurements on Doublet III armor tile graphite

SciTech Connect

Doll, D.W.; Reis, E.

1983-12-01

Several tests were performed on the Doublet III wall armor tiles to determine the cool-down rate and to evaluate improvements made by changing the conditions at the interface between the graphite tile and the stainless steel backing plate. Thermal diffusivity tests were performed in vacuum on both TiC coated and bare graphite tiles with and without 0.13 mm (.005'') thick silver foil at the interface. The results of the armor tile cool-down tests showed improvement when a 0.13 mm (0.005'') silver foil is used at the interface. At 2.1 x 10/sup 5/ Pa (30 psi) contact pressure, the e-folding cool-down times for a TiC coated tile, bare graphite and bare graphite with a 0.06 mm (0.0035'') silver shim were 10 min., 5.0 min., and 4.1 min., respectively. Tests using high contact pressures showed that the cool-down rates converged to approx. 4.0 min. At this limit, the conduction path along the backing plate to the two cooling tubes controls the heat flow, and no further improvement could be expected. Thermal diffusivity measurements confirmed the results of the cool-down test showing that by introducing a silver foil at the interface, the contact conductance between Poco AXF-5Q graphite and 316 stainless steel could be improved by a factor of three to eight. The tests showed an increasing improvement over a range of temperatures from 25/sup 0/C to 400/sup 0/C. The data provides a technical basis for further applications of graphite tiles to cooled backing plates.

14. Gamma-Ray Light Curves from Pulsar Magnetospheres with Finite Conductivity

NASA Technical Reports Server (NTRS)

Harding, A. K.; Kalapotharakos, C.; Kazanas, D.; Contopoulos, I.

2012-01-01

The Fermi Large Area Telescope has provided an unprecedented database for pulsar emission studies that includes gamma-ray light curves for over 100 pulsars. Modeling these light curves can reveal and constrain the geometry of the particle accelerator, as well as the pulsar magnetic field structure. We have constructed 3D magnetosphere models with finite conductivity, that bridge the extreme vacuum and force-free solutions used in previous light curves modeling. We are investigating the shapes of pulsar gamma-ray light curves using these dissipative solutions with two different approaches: (l) assuming geometric emission patterns of the slot gap and outer gap, and (2) using the parallel electric field provided by the resistive models to compute the trajectories and . emission of the radiating particles. The light curves using geometric emission patterns show a systematic increase in gamma-ray peak phase with increasing conductivity, introducing a new diagnostic of these solutions. The light curves using the model electric fields are very sensitive to the conductivity but do not resemble the observed Fermi light curves, suggesting that some screening of the parallel electric field, by pair cascades not included in the models, is necessary

15. X-ray measurements of water fog density. [PWR; BWR

SciTech Connect

Camp, A.L.

1982-11-01

Water-fog densities were measured in a laboratory experiment using x-ray diagnostics. Fog densities were measured, varying the flow rate, nozzle type, nozzle configuration, nozzle height above the x-ray beam, and water surface tension. Suspended water volume fractions between 0.0008 and 0.0074 percent were measured. The fog density increases approximately as the square root of the flow rate; the other parameters had little effect on the density.

16. Measurement of 238U muonic x-rays with a germanium detector setup

SciTech Connect

Esch, Ernst I; Jason, Andrew; Miyadera, Haruo; Hoteling, Nathan J; Heffner, Robert H; Adelmann, Andreas; Stocki, Trevor; Mitchell, Lee

2009-01-01

In the field of nuclear non-proliferation muon interactions with materials are of great interest. This paper describes an experiment conducted at the Paul Scherrer Institut (PSI) in Switzerland where a muon beam is stopped in a uranium target. The muons produce characteristic muonic x-rays. Muons will penetrate shielding easily and the produced characteristic x-rays can be used for positive isotope identification. Furthermore, the x-rays for uranium isotopes lie in the energy range of 6-7 MeV, which allows them to have an almost optimal mean free path in heavy shielding such as lead or steel. A measurement was conducted at PSI to prove the feasibility of detecting muonic x-rays from a large sample of depleted uranium (several kilograms) with a germanium detector. In this paper, the experimental setup and analysis of the measurement itself is presented.

17. Strain measurement of pure titanium covered with soft tissue using X-ray diffraction.

PubMed

2010-03-01

Measurement of the stress and strain applied to implants and bone tissue in the human body are important for fracture prediction and evaluations of implant adaptation. The strain of titanium (Ti) materials can be measuring by X-ray diffraction techniques. This study applied X-ray diffraction to the skin tissue-covered Ti. Characteristic X-rays of Mo Kalpha were used and the X-rays diffracted from the Ti were detected through the covering skin tissue. The X-ray absorption by skin tissue is large under the diffracted X-rays detected in low angles because the length of penetration depends on the angle of inclination, equal to the Bragg angle. The effects of skin tissue to detect the diffracted X-rays were investigated in the experiments. And the strain measurements were conducted under bending loads applied to the Ti specimen. The effect of skin tissue was absorption of X-rays as well as the X-rays scattered from the physiological saline contained in the tissue. The X-rays scattered by the physiological saline creates a specific background pattern near the peaks from the (002) and (011) lattice planes of Ti in the X-ray diffraction profile. Diffracted X-rays from the Ti were detected after being transmitted through 1 mm thick skin tissue by Mo Kalpha. Individual peaks such as (010), (002), (011), and (110) were clearly established by using a parallel beam arrangement. The strains of (110) lattice planes were measured with or without the tissue cover were very similar. The strain of the (110) lattice planes of Ti could be measured by Mo Kalpha when the Ti specimen was located under the skin tissue. PMID:20459192

18. Measuring high-energy {gamma} rays with Ge detectors

SciTech Connect

Lipoglavsek, M.; Likar, A.; Vencelj, M.; Vidmar, T.; Bark, R. A.; Gueorguieva, E.; Komati, F.; Lawrie, J. J.; Maliage, S. M.; Mullins, S. M.; Murray, S. H. T.; Ramashidzha, T. M.

2006-04-26

Gamma rays with energies up to 21 MeV were measured with Ge detectors. Such {gamma} rays were produced in the 208Pb(p,{gamma})209Bi reaction. The position of the 2g9/2 single proton orbit in 209Bi has been determined indicating the size of the Z=126 shell gap.

19. X-Ray Measurements Of Displacements In Hostile Environments

NASA Technical Reports Server (NTRS)

Fralick, Gustave C.; Canistraro, Howard A.; Jordan, Eric H.; Pease, Douglas M.

1995-01-01

Developmental method of noncontact extensometry of objects in hot or otherwise hostile environments based on focusing and scanning of x rays. Principal advantage: ability to make measurements through stratified and/or flowing gases, smoke, and flames, as well as through solid layers of x-ray-transparent materials.

20. QUALITY CONTROL FOR ENVIRONMENTAL MEASUREMENTS USING GAMMA-RAY SPECTROMETRY

EPA Science Inventory

This report describes the quality control procedures, calibration, collection, analysis, and interpretation of data in measuring the activity of gamma ray-emitting radionuclides in environmental samples. Included in the appendices are basic data for selected gamma ray-emitting ra...

1. Steady heat conduction-based thermal conductivity measurement of single walled carbon nanotubes thin film using a micropipette thermal sensor

Shrestha, R.; Lee, K. M.; Chang, W. S.; Kim, D. S.; Rhee, G. H.; Choi, T. Y.

2013-03-01

In this paper, we describe the thermal conductivity measurement of single-walled carbon nanotubes thin film using a laser point source-based steady state heat conduction method. A high precision micropipette thermal sensor fabricated with a sensing tip size varying from 2 μm to 5 μm and capable of measuring thermal fluctuation with resolution of ±0.01 K was used to measure the temperature gradient across the suspended carbon nanotubes (CNT) film with a thickness of 100 nm. We used a steady heat conduction model to correlate the temperature gradient to the thermal conductivity of the film. We measured the average thermal conductivity of CNT film as 74.3 ± 7.9 W m-1 K-1 at room temperature.

2. Steady heat conduction-based thermal conductivity measurement of single walled carbon nanotubes thin film using a micropipette thermal sensor.

PubMed

Shrestha, R; Lee, K M; Chang, W S; Kim, D S; Rhee, G H; Choi, T Y

2013-03-01

In this paper, we describe the thermal conductivity measurement of single-walled carbon nanotubes thin film using a laser point source-based steady state heat conduction method. A high precision micropipette thermal sensor fabricated with a sensing tip size varying from 2 μm to 5 μm and capable of measuring thermal fluctuation with resolution of ±0.01 K was used to measure the temperature gradient across the suspended carbon nanotubes (CNT) film with a thickness of 100 nm. We used a steady heat conduction model to correlate the temperature gradient to the thermal conductivity of the film. We measured the average thermal conductivity of CNT film as 74.3 ± 7.9 W m(-1) K(-1) at room temperature. PMID:23556837

3. Dynamics and X-ray emission of an X-pinch conducted on a small capacitive generator

Pavez, Cristian; Avaria, Gonzalo; Moreno, Jose; San Martin, Patricio; Soto, Leopoldo; Sepulveda, Adolfo; Pedreros, Jose

2014-10-01

The characterization of the dynamics and X-ray emission of a X-pinch configuration conducted in a compact capacitive generator are presented. The experimental measurements were carried out on a multi-purpose generator (1.2 micro F, 345 J, 47.5 nH, T/4 = 375 ns and Z = 0.2 Ohm in short circuit) which produces currents up to 122 kA with 500 ns quarter period, when wire load are used. Dark-field Schlieren and interferometry techniques were used to characterize the dynamics of the precursor plasma, plasma flares and plasma jet on the axes. The X-ray emission and the source size are evaluated with filtered PIN-diodes and aperture imaging technique respectively. In addition, X-ray plasma imaging and radiographic applications are presented. The experiments were conducted on W wires of different diameters. The experimental observations show a similar dynamic to those observed in experiments of higher current and shorter quarter period. Work supported by PIA CONICYT Grant ACT-1115, PAI CONICYT 791100020 and FONDECYT Iniciacion 11121587.

4. X-ray Pinhole Camera Measurements

SciTech Connect

Nelson, D. S.; Berninger, M. J.; Flores, P. A.; Good, D. E.; Henderson, D. J.; Hogge, K. W.; Huber, S. R.; Lutz, S. S.; Mitchell, S. E.; Howe, R. A.; Mitton, C. V.; Molina, I.; Bozman, D. R.; Cordova, S. R.; Mitchell, D. R.; Oliver, B. V.; Ormond, E. C.

2013-06-20

The rod pinch diode is made up of a cathode plate and a small diameter anode rod that extends through the cathode hole. The anode is charged positively. The rod tip is made of a high-z material which is chosen for its bremsstrahlung efficiency. When the diode is pulsed it produces an intense x-ray source used for pulsed radiography. The baseline or reference diode consists of a 0.75 mm diameter Tungsten (W) tapered anode rod which extends 10 mm through a 9 mm diameter 3 mm thick aluminum (Al) aperture. The majority of the current in the electron beam is created on the edges of the cathode aperture and when properly configured, the electrons will self insulate, travel down the extension of the rod, and pinch onto the tip of the rod. In this presentation, performance of hybrid diodes will be compared with the baseline diode.

5. SPHINX Measurements of Radiation Induced Conductivity of Foam

SciTech Connect

Ballard, W.P.; Beutler, D.E.; Burt, M.; Dudley, K.J.; Stringer, T.A.

1998-12-14

Experiments on the SPHINX accelerator studying radiation-induced conductivity (RIC) in foam indicate that a field-exclusion boundary layer model better describes foam than a Maxwell-Garnett model that treats the conducting gas bubbles in the foam as modifying the dielectric constant. In both cases, wall attachment effects could be important but were neglected.

6. Gamma-ray dosimetry measurements of the Little Boy replica

SciTech Connect

Plassmann, E.A.; Pederson, R.A.

1984-01-01

We present the current status of our gamma-ray dosimetry results for the Little Boy replica. Both Geiger-Mueller and thermoluminescent detectors were used in the measurements. Future work is needed to test assumptions made in data analysis.

7. Conductivity tensor of graphene through reflection of microwave measurements

Meera, V.; Setlur, Girish S.

2009-03-01

The optical response of free standing graphene, with or without a perpendicular magnetic field, doping or gap, is studied theoretically by solving Maxwell's equations. Formulae for the reflection coefficient and the reflected polarization are derived in terms of the polarization of the incident electromagnetic wave in the microwave region, its angle of incidence and the azimuthal angle on the graphene plane. These formulae involve the conductivity tensor of graphene. The behaviour of the reflection coefficient and the reflected polarization with the variation of these parameters may be used to infer the optical conductivity tensor and the anisotropy of the conductivity (by this we mean the presence of non-vanishing off-diagonal components of the conductivity tensor). The conductivity of graphene is important since it provides indirect evidence of the effective relativistic dispersion of the energy of the quasi-particles involved.

8. Measurement of γ rays from μ^- capture on ^14N

Stocki, T. J.; Gete, E.; Lange, J.; Measday, D. F.; Moftah, B. A.; Saliba, M. A.; Gorringe, T. P.

1997-10-01

A μ^- beam produced at TRIUMF was stopped in a liquid nitrogen target and the γ-rays produced by μ^- capture on ^14N were measured using two HPGe detectors in a back-to-back geometry. Each HPGe detector was surrounded by a NaI annulus to veto γ-rays Compton scattered from the Ge detector. Each HPGe also had a plastic scintillator in front of it, to eliminate the background from muon decay electrons. Using this technique the following ^14C muon capture γ-rays have been observed: 809, 6092, and 6727 keV. The 7010 keV line, which has been seen before,(M.Giffon et al., Phys. Rev. C \\underline24, 241 (1981). ) was also observed. Gamma rays from ^13C have been observed for the first time. The yields of these γ-rays have been measured.

9. Ground level measurements of air conductivities under Florida thunderstorms

NASA Technical Reports Server (NTRS)

Blakeslee, Richard J.; Krider, E. P.

1992-01-01

Values of the positive and negative polar conductivities under summer thunderstorms in Florida are highly variable and exhibit a significant electrode effect, but the total conductivity usually remains close to values found in fair weather, 0.4 to 1.8 x 10 exp -14 S/m. With these values a method proposed by Krider and Musser (1982) for estimating the total conductivity from changes in the slope of the electric field recovery following a lightning discharge will be extremely sensitive to small time variations in the local Maxwell current density and must be modified to include these effects.

10. In vivo measurements of electrical conductivity of porcine organs at low frequency: new method of measurement.

PubMed

Spottorno, J; Multigner, M; Rivero, G; Alvarez, L; de la Venta, J; Santos, M

2012-10-01

Calculations of the induced currents created in the human body by external electromagnetic fields would be more accurate provided that more realistic experimental values of the electrical properties of the body were available. The purpose of this work is to experimentally obtain values for the conductivity of living organs in conditions close to the real situation. Two-electrode in vivo measurements of the bioimpedance of some porcine organs have been performed. From these measurements and taking into account geometrical considerations, the electrical conductivity for the kidney, liver, heart, and spinal cord has been obtained and were found to be higher than the values reported in the literature. Furthermore, a new experimental procedure is proposed where the conductivity is determined from the values of the electrical potential and currents that are induced by an external electromagnetic field created by a coil placed close to the organ under study. PMID:22430866

11. Laboratory Measurements of the X-ray Line Emission from Neon-like Fe XVII

NASA Technical Reports Server (NTRS)

Brown, G. V.; Beiersdorfer, P.; Chen, H.; Scofield, J. H.; Boyce, K. R.; Kelley, R. L.; Kilbourne, C. A.; Porter, F. S.; Gu, M. F.; Kahn, S. M.

2006-01-01

We have conducted a systematic study of the dominant x-ray line emission from Fe XVII. These studies include relative line intensities in the optically thin limit, intensities in the presence of radiation from satellite lines from lower charge states of iron, and the absolute excitation cross sections of some of the strongest lines. These measurements were conducted at the Lawrence Livermore National Laboratory electron beam ion trap facility using crystal spectrometers and a NASA-Goddard Space Flight Center microcalorimeter array.

12. Innovative Gamma Ray Spectrometer Detection Systems for Conducting Scanning Surveys on Challenging Terrain - 13583

SciTech Connect

Palladino, Carl; Mason, Bryan; Engle, Matt; LeVangie, James; Dempsey, Gregg; Klemovich, Ron

2013-07-01

The Santa Susana Field Laboratory located near Simi Valley, California was investigated to determine the nature and extent of gamma radiation anomalies. The primary objective was to conduct gamma scanning surveys over 100 percent of the approximately 1,906,000 square meters (471 acre) project site with the most sensitive detection system possible. The site had challenging topography that was not conducive to traditional gamma scanning detection systems. Terrain slope varied from horizontal to 48 degrees and the ground surface ranged from flat, grassy meadows to steep, rocky hillsides. In addition, the site was home to many protected endangered plant and animal species, and archaeologically significant sites that required minimal to no disturbance of the ground surface. Therefore, four innovative and unique gamma ray spectrometer detection systems were designed and constructed to successfully conduct gamma scanning surveys of approximately 1,076,000 square meters (266 acres) of the site. (authors)

13. Direct measurement of ion mobility in a conducting polymer.

PubMed

Stavrinidou, Eleni; Leleux, Pierre; Rajaona, Harizo; Khodagholy, Dion; Rivnay, Jonathan; Lindau, Manfred; Sanaur, Sébastien; Malliaras, George G

2013-08-27

Using planar junctions between the conducting polymer PEDOT:PSS and various electrolytes, it is possible to inject common ions and directly observe their transit through the film. The 1D geometry of the experiment allows a straightforward estimate of the ion drift mobilities. PMID:23784809

14. EVALUATION OF HYDRAULIC CONDUCTIVITIES CALCULATED FROM MULTIPORT-PERMEAMETER MEASUREMENTS

EPA Science Inventory

A multiport permeameter was developed for use in estimating hydraulic conductivity over intact sections of aquifer core using the core liner as the permeameter body. Six cores obtained from one borehole through the upper 9 m of a stratified glacial-outwash aquifer were used to ev...

15. Measuring x-ray spectra of flash radiographic sources

SciTech Connect

Gehring, Amanda Elizabeth; Espy, Michelle A.; Haines, Todd Joseph; Mendez, Jacob; Moir, David C.; Sedillo, Robert; Shurter, Roger P.; Volegov, Petr Lvovich; Webb, Timothy J

2015-11-02

The x-ray spectra of flash radiographic sources is difficult to measure. The sources measured were Radiographic Integrated Test Stand-6 (370 rad at 1 m; 50 ns pulse) and Dual Axis Radiographic Hydrodynamic Test Facility (DARHT) (550 rad at 1 m; 50 ns pulse). Features of the Compton spectrometer are described, and spectra are shown. Additional slides present data on instrumental calibration.

16. Measurement and characterization of x-ray spot size

SciTech Connect

Mueller, K.H.

1989-01-01

In planning an x-ray imaging experiment one must have an accurate model of the imaging system to obtain optimum results. The blurring caused by the finite size of the x-ray source is often the least understood element in the system. We have developed experimental and analytical methods permitting accurate measurement and modeling of the x-ray source. The model offers a simple and accurate way to optimize the radiographic geometry for any given experimental requirement (i.e., resolution and dose at detector). Any text on radiography will mention the effects of the finite size of the x-ray source on image quality and how one can minimize this influence by the choice of a small radiographic magnification. The film blur (independent of the source blur) is often treated as a single number and combined with an effective blur dimension for the x-ray source to give a total blur on the film. In this paper, we will develop a treatment of x-ray sources based on the modulation transfer function (MTF). This approach allows us to infer the spatial distribution function of the electron beam that produces the bremsstrahlung x-rays and to predict the performance of an x-ray imaging system if we know the MTF of the detector. This treatment is much more accurate than a single number characterization. 4 refs., 7 figs.

17. Contactless measurement of alternating current conductance in quantum Hall structures

SciTech Connect

Drichko, I. L.; Diakonov, A. M.; Malysh, V. A.; Smirnov, I. Yu.; Ilyinskaya, N. D.; Usikova, A. A.; Galperin, Y. M.; Kummer, M.; Känel, H. von

2014-10-21

We report a procedure to determine the frequency-dependent conductance of quantum Hall structures in a broad frequency domain. The procedure is based on the combination of two known probeless methods—acoustic spectroscopy and microwave spectroscopy. By using the acoustic spectroscopy, we study the low-frequency attenuation and phase shift of a surface acoustic wave in a piezoelectric crystal in the vicinity of the electron (hole) layer. The electronic contribution is resolved using its dependence on a transverse magnetic field. At high frequencies, we study the attenuation of an electromagnetic wave in a coplanar waveguide. To quantitatively calibrate these data, we use the fact that in the quantum-Hall-effect regime the conductance at the maxima of its magnetic field dependence is determined by extended states. Therefore, it should be frequency independent in a broad frequency domain. The procedure is verified by studies of a well-characterized p-SiGe/Ge/SiGe heterostructure.

18. Astronaut Mike Fincke Conducts Fluid Merging Viscosity Measurement (FMVM) Experiment

NASA Technical Reports Server (NTRS)

2004-01-01

Astronaut Mike Fincke places droplets of honey onto the strings for the Fluid Merging Viscosity Measurement (FMVM) investigation onboard the International Space Station (ISS). The FMVM experiment measures the time it takes for two individual highly viscous fluid droplets to coalesce or merge into one droplet. Different fluids and droplet size combinations were tested in the series of experiments. By using the microgravity environment, researchers can measure the viscosity or 'thickness' of fluids without the influence of containers and gravity using this new technique. Understanding viscosity could help scientists understand industrially important materials such as paints, emulsions, polymer melts and even foams used to produce pharmaceutical, food, and cosmetic products.

19. Instrument for Measuring Thermal Conductivity of Materials at Low Temperatures

NASA Technical Reports Server (NTRS)

Fesmire, James; Sass, Jared; Johnson, Wesley

2010-01-01

With the advance of polymer and other non-metallic material sciences, whole new series of polymeric materials and composites are being created. These materials are being optimized for many different applications including cryogenic and low-temperature industrial processes. Engineers need these data to perform detailed system designs and enable new design possibilities for improved control, reliability, and efficiency in specific applications. One main area of interest is cryogenic structural elements and fluid handling components and other parts, films, and coatings for low-temperature application. An important thermal property of these new materials is the apparent thermal conductivity (k-value).

20. Research on temperature measurement by X-ray transmission intensity

Chen, Shuyue; Cheng, Rong

2013-02-01

The relationship between temperature and X-ray transmission intensity was researched and analyzed by inspecting material density change, which is caused by thermal expansion. A digital radiographic system was employed to obtain the images. On this basis, we deduced the temperature formula based on the average gray level of the captured images. The measured temperatures were obtained from the experiments and the errors were analyzed. We concluded that when X-rays pass through an object, the X-ray strength and the gray level of the image under high temperatures are greater than those under lower temperatures and the image gray level error has great impact on the accuracy of the measured temperature. The presented approach allowed the non-contact temperature measurement of material.

1. On Measuring Cosmic Ray Energy Spectra with the Rapidity Distributions

NASA Technical Reports Server (NTRS)

Bashindzhagyan, G.; Adams, J.; Chilingarian, A.; Drury, L.; Egorov, N.; Golubkov, S.; Korotkova, N.; Panasyuk, M.; Podorozhnyi, D.; Procqureur, J.

2000-01-01

An important goal of cosmic ray research is to measure the elemental energy spectra of galactic cosmic rays up to 10(exp 16) eV. This goal cannot be achieved with an ionization calorimeter because the required instrument is too massive for space flight. An alternate method will be presented. This method is based on measuring the primary particle energy by determining the angular distribution of secondaries produced in a target layer. The proposed technique can be used over a wide range of energies (10 (exp 11) -10 (exp 16) eV) and gives an energy resolution of 60% or better. Based on this technique, a conceptual design for a new instrument (KLEM) will be presented. Due to its light weight, this instrument can have a large aperture enabling the direct measurement of cosmic rays to 1016 eV.

2. Nanoscale Electromechanics To Measure Thermal Conductivity, Expansion, and Interfacial Losses.

PubMed

Mathew, John P; Patel, Raj; Borah, Abhinandan; Maliakkal, Carina B; Abhilash, T S; Deshmukh, Mandar M

2015-11-11

We study the effect of localized Joule heating on the mechanical properties of doubly clamped nanowires under tensile stress. Local heating results in systematic variation of the resonant frequency; these frequency changes result from thermal stresses that depend on temperature dependent thermal conductivity and expansion coefficient. The change in sign of the linear expansion coefficient of InAs is reflected in the resonant response of the system near a bath temperature of 20 K. Using finite element simulations to model the experimentally observed frequency shifts, we show that the thermal conductivity of a nanowire can be approximated in the 10-60 K temperature range by the empirical form κ = bT W/mK, where the value of b for a nanowire was found to be b = 0.035 W/mK(2), significantly lower than bulk values. Also, local heating allows us to independently vary the temperature of the nanowire relative to the clamping points pinned to the bath temperature. We suggest a loss mechanism (dissipation ~10(-4)-10(-5)) originating from the interfacial clamping losses between the metal and the semiconductor nanostructure. PMID:26479952

3. Thermal conductivity of silver loaded conductive epoxy from cryogenic to ambient temperature and its application for precision cryogenic noise measurements

Amils, Ricardo I.; Gallego, Juan Daniel; Sebastián, José Luis; Muñoz, Sagrario; Martín, Agustín; Leuther, Arnulf

2016-06-01

The pressure to increase the sensitivity of instrumentation has pushed the use of cryogenic Low Noise Amplifier (LNA) technology into a growing number of fields. These areas range from radio astronomy and deep space communications to fundamental physics. In this context manufacturing for cryogenic environments requires a proper thermal knowledge of the materials to be able to achieve adequate design behavior. In this work, we present experimental measurements of the thermal conductivity of a silver filled conductive epoxy (EPO-TEK H20E) which is widely used in cryogenic electronics applications. The characterization has been made using a sample preparation which mimics the practical use of this adhesive in the fabrication of cryogenic devices. We apply the data obtained to a detailed analysis of the effects of the conductive epoxy in a monolithic thermal noise source used for high accuracy cryogenic microwave noise measurements. In this application the epoxy plays a fundamental role since its limited thermal conductivity allows heating the chip with relatively low power. To our knowledge, the cryogenic thermal conductivity data of this epoxy has not been reported before in the literature in the 4-300 K temperature range. A second non-conductive epoxy (Gray Scotch-Weld 2216 B/A), also widely used in cryogenic applications, has been measured in order to validate the method by comparing with previous published data.

4. Portable x-ray fluorescence spectrometer for coating thickness measurement

SciTech Connect

Carapelle, Alain; Fleury-Frenette, Karl; Collette, Jean-Paul; Garnir, Henri-Pierre; Harlet, Philippe

2007-12-15

A handheld x-ray spectrometer has been realized and tested. The purpose of the device is to measure the thickness of coated samples in the range of 1-1500 nm in an industrial environment. Accuracy of {approx}3% has been achieved in this range with a measurement time of 1 min. Automated software has been implemented to allow utilization by a nonspecialist operator. An automated calibration procedure, based on measurements of reference samples, is used.

5. A New Measurement of the Cosmic X-ray Background

SciTech Connect

Moretti, A.

2009-05-11

I present a new analytical description of the cosmic X-ray background (CXRB) spectrum in the 1.5-200 keV energy band, obtained by combining the new measurement performed by the Swift X-ray telescope (XRT) with the recently published Swift burst alert telescope (BAT) measurement. A study of the cosmic variance in the XRT band (1.5-7 keV) is also presented. I find that the expected cosmic variance (expected from LogN-LogS) scales as {omega}{sup -0.3}(where {omega} is the surveyed area) in very good agreement with XRT data.

6. MEASUREMENT OF HYDRAULIC CONDUCTIVITY DISTRIBUTIONS: A MANUAL OF PRACTICE

EPA Science Inventory

The ability of hydrologists to perform field measurements of aquifer hydraulic properties must be enhanced in order to significantly improve the capacity to solve groundwater contamination problems at Superfund and other sites. The primary purpose of this manual is to provide ne...

7. MEASUREMENT OF HYDRAULIC CONDUCTIVITY DISTRIBUTIONS: A MANUAL OF PRACTICE

EPA Science Inventory

The ability of hydrologists to perform field measurements of aquifer hydraulic properties must be enhanced in order to significantly improve the capacity to solve groundwater contamination problems at Superfund and other sites. he primary purpose of this manual is to provide new ...

8. Conducting Art Therapy Research Using Quantitative EEG Measures

ERIC Educational Resources Information Center

Belkofer, Christopher M.; Konopka, Lukasz M.

2008-01-01

This study presents a modified, single subject design that measured the patterns of electrical activity of a participant's brain following an hour spent painting and drawing. Paired t tests were used to compare pre and post art-making electroencephalograph (EEG) data. The results indicated that neurobiological activity after drawing and painting…

9. Measuring Thermal Conductivity of a Small Insulation Sample

NASA Technical Reports Server (NTRS)

Miller, Robert A.; Kuczmarski, Maria A.

2009-01-01

A multiple-throat venturi system has been invented for measuring laminar flow of air or other gas at low speed (1 to 30 cm/s) in a duct while preserving the laminar nature of the flow and keeping the velocity profile across the duct as nearly flat as possible. While means for measuring flows at higher speeds are well established, heretofore, there have been no reliable means for making consistent, accurate measurements in this speed range. In the original application for which this system was invented, the duct leads into the test section of a low-speed wind tunnel wherein uniform, low-speed, laminar flow is required for scientific experiments. The system could also be used to monitor a slow flow of gas in an industrial process like chemical vapor deposition. In the original application, the multiple- throat venturi system is mounted at the inlet end of the duct having a rectangular cross section of 19 by 14 cm, just upstream of an assembly of inlet screens and flow straighteners that help to suppress undesired flow fluctuations (see Figure 1). The basic venturi measurement principle is well established: One measures the difference in pressure between (1) a point just outside the inlet, where the pressure is highest and the kinetic energy lowest; and (2) the narrowest part (the throat) of the venturi passage, where the kinetic energy is highest and the pressure is lowest. Then by use of Bernoulli s equation for the relationship between pressure and kinetic energy, the volumetric flow speed in the duct can be calculated from the pressure difference and the inlet and throat widths. The design of this system represents a compromise among length, pressure recovery, uniformity of flow, and complexity of assembly. Traditionally, venturis are used to measure faster flows in narrower cross sections, with longer upstream and downstream passages to maintain accuracy. The dimensions of the passages of the present venturi system are sized to provide a readily measurable

10. Simultaneous measurement of peritoneal glucose and free water osmotic conductances.

PubMed

La Milia, V; Limardo, M; Virga, G; Crepaldi, M; Locatelli, F

2007-09-01

Ultrafiltration (UF) failure is one of the most important causes of long-term peritoneal dialysis (PD) failure in patients. Osmotic forces acting across small and ultra-small pores generate a UF with solutes through the small pore and free water transport (FWT) through the ultra-small pore. The ability of glucose to exert an osmotic pressure sufficient to cause UF is the so-called 'osmotic conductance to glucose' (OCG) of the peritoneal membrane. Our study proposes a simple method to determine both the OCG and FWT. In 50 patients on PD, a Double Mini-Peritoneal Equilibration Test (Double Mini-PET), consisting of two Mini-PET, was performed consecutively. A solution of 1.36% glucose was used for the first test, whereas a solution of 3.86% glucose was used for the second test. The sodium removal values and the differences in UF between the two tests were used to calculate FWT and the OCG. Patients with UF failure showed significant reductions not only in the OCG and the FWT but also of UF of small pores. The Double Mini-PET is simple, fast, and could become useful to evaluate patients on PD in everyday clinical practice. PMID:17609692

11. Cosmic rays muon flux measurements at Belgrade shallow underground laboratory

SciTech Connect

Veselinović, N. Dragić, A. Maletić, D. Joković, D. Savić, M. Banjanac, R. Udovičić, V. Aničin, I.

2015-02-24

The Belgrade underground laboratory is a shallow underground one, at 25 meters of water equivalent. It is dedicated to low-background spectroscopy and cosmic rays measurement. Its uniqueness is that it is composed of two parts, one above ground, the other bellow with identical sets of detectors and analyzing electronics thus creating opportunity to monitor simultaneously muon flux and ambient radiation. We investigate the possibility of utilizing measurements at the shallow depth for the study of muons, processes to which these muons are sensitive and processes induced by cosmic rays muons. For this purpose a series of simulations of muon generation and propagation is done, based on the CORSIKA air shower simulation package and GEANT4. Results show good agreement with other laboratories and cosmic rays stations.

12. Trek and ECCO: Abundance measurements of ultraheavy galactic cosmic rays

Westphal, Andrew J.

2000-06-01

Using the Trek detector, we have measured the abundances of the heaviest elements (with Z>70) in the galactic cosmic rays with sufficient charge resolution to resolve the even-Z elements. We find that the abundance of Pb compared to Pt is ~3 times lower than the value expected from the most widely-held class of models of the origin of galactic cosmic ray nuclei, that is, origination in a partially ionized medium with solar-like composition. The low abundance of Pb is, however, consistent with the interstellar gas and dust model of Meyer, Drury and Ellison, and with a source enriched in r-process material, proposed by Binns et al. A high-resolution, high-statistics measurement of the abundances of the individual actinides would distinguish between these models. This is the goal of ECCO, the Extremely Heavy Cosmic-ray Composition Observer, which we plan to deploy on the International Space Station. .

13. GAMMA-RAY LIGHT CURVES FROM PULSAR MAGNETOSPHERES WITH FINITE CONDUCTIVITY

SciTech Connect

Kalapotharakos, Constantinos; Harding, Alice K.; Kazanas, Demosthenes

2012-07-20

We investigate the shapes of {gamma}-ray pulsar light curves using three-dimensional pulsar magnetosphere models of finite conductivity. These models, covering the entire spectrum of solutions between vacuum and force-free magnetospheres, for the first time afford mapping the GeV emission of more realistic, dissipative pulsar magnetospheres. To this end we generate model light curves following two different approaches: (1) We employ the emission patterns of the slot and outer gap models in the field geometries of magnetospheres with different conductivity {sigma}. (2) We define realistic trajectories of radiating particles in magnetospheres of different {sigma} and compute their Lorentz factor under the influence of magnetospheric electric fields and curvature radiation-reaction; with these at hand we then calculate the emitted radiation intensity. The light curves resulting from these prescriptions are quite sensitive to the value of {sigma}, especially in the second approach. While still not self-consistent, these results are a step forward in understanding the physics of pulsar {gamma}-radiation.

14. Systematic Effects on Duration Measurements of Gamma-Ray Bursts

NASA Technical Reports Server (NTRS)

Koshut, Thomas M.; Paciesas, William S.; Kouveliotou, Chryssa; vanParadijs, Jan; Pendleton, Geoffrey N.; Fishman, Gerald J.; Meegan, Charles A.

1996-01-01

The parameters T(sub 90) and T(sub 50) have recently been introduced as a measurement of the duration of gamma-ray bursts. We present here a description of the method of measuring T(sub 90) and T(sub 50) and its application to gamma-ray bursts observed with the Burst and Transient Source Experiment (BATSE) onboard the Compton Gamma-Ray Observatory (CGRO). We use simulated as well as observed time profiles to address some of the possible systematic effects affecting individual T(sub 90) (T(sub 50)) measurements. We show that these systematic effects do not mimic those effects that would result from time dilation if the burst sources are at distances of several Gpc. We discuss the impact of these systematic effects on the T(sub 90) (T(sub 50)) distributions for the gamma-ray bursts observed with BATSE. We distinguish between various types of T(sub 90) (T(sub 50)) distributions, and discuss the ways in which distributions observed with different experiments can vary, even though the measurements for commonly observed bursts may be the same. We then discuss the distributions observed with BATSE and compare them to those observed with other experiments.

15. Incorporating Vertical Ray-Path Measurements in Crosshole Radar Tomography

Day-Lewis, F. D.; Boyden, C. L.; Lane, J. W., Jr.

2015-12-01

Image resolution for crosshole radar tomography depends on survey geometry, measurement errors, regularization, prior information, and the physics underlying measurements. In acquisition of crosshole radar surveys, in-well measurements along vertical ray paths are rarely considered. Radar logging, in which the transmitting and receiving antennas are moved in tandem within a single borehole, can be used to generate pseudo logs of slowness and attenuation. Given that crosshole radar tomographic resolution tends to be best towards the center of the interwell region and poorer at boreholes, in-well travel-time and amplitude data represent valuable additional sources of information to improve radar tomographic imaging. Here, we assess the information content of data collected along in-well vertical ray paths. We quantify information content using metrics based on the model resolution matrix and correlation loss. Substantial improvements in crosshole inversion results are possible with consideration of in-well radar measurement data.

16. Gamma Ray Mirrors for Direct Measurement of Spent Nuclear Fuel

SciTech Connect

Pivovaroff, Dr. Michael J.; Ziock, Klaus-Peter; Harrison, Mark J; Soufli, Regina

2014-01-01

Direct measurement of the amount of Pu and U in spent nuclear fuel represents a challenge for the safeguards community. Ideally, the characteristic gamma-ray emission lines from different isotopes provide an observable suitable for this task. However, these lines are generally lost in the fierce flux of radiation emitted by the fuel. The rates are so high that detector dead times limit measurements to only very small solid angles of the fuel. Only through the use of carefully designed view ports and long dwell times are such measurements possible. Recent advances in multilayer grazing-incidence gamma-ray optics provide one possible means of overcoming this difficulty. With a proper optical and coating design, such optics can serve as a notch filter, passing only narrow regions of the overall spectrum to a fully shielded detector that does not view the spent fuel directly. We report on the design of a mirror system and a number of experimental measurements.

17. Studying Stratospheric Temperature Variation with Cosmic Ray Measurements

Zhang, Xiaohang; He, Xiaochun

2015-04-01

The long term stratospheric cooling in recent decades is believed to be equally important as surface warming as evidence of influences of human activities on the climate system. Un- fortunatly, there are some discrepancies among different measurements of stratospheric tem- peratures, which could be partially caused by the limitations of the measurement techniques. It has been known for decades that cosmic ray muon flux is sensitive to stratospheric temperature change. Dorman proposed that this effect could be used to probe the tempera- ture variations in the stratophere. In this talk, a method for reconstructing stratospheric temperature will be discussed. We verify this method by comparing the stratospheric tem- perature measured by radiosonde with the ones derived from cosmic ray measurement at multiple locations around the globe.

18. Student Measurements of Cosmic Rays on an International Scale

Peterson, Robert S.

2006-12-01

As part of the QuarkNet Collaboration, teachers and students capture cosmic ray data using scintillator hardware the students construct. These data support student inquiry into cosmic ray flux, provide coincidence timing of cosmic ray showers, measure muon lifetime, and analyze their cosmic ray detector performance. Students share these data with others by using a browser friendly “e-Lab” portal. After three years, the QuarkNet “e-Lab” portal contains over 7000 days of cosmic ray data from 70 high schools. The nature of web based tools and data retrieval allow anyone with an Internet connection to engage freely the available resources investigating cosmic rays. The Internet now allows international students to participate in the Collaboration. With the coming of the LHC in CERN and plans underway for siting the ILC, particle physics includes more international institutions. QuarkNet supports this international effort by sharing resources with teachers and students abroad. This talk examines the new inclusion of distant students who contribute their data from around the globe with time synchronous coverage. Simultaneous data strengthens the questions students can examine. Examples of global research questions will be covered, and examples given of student research. Additional international members may join; account procedures will be described.

19. X-ray diffraction measurement of residual stresses in thick, multi-pass steel weldments

SciTech Connect

Ruud, C.O.; Di Mascio, P.S.; Pangborn, R.N.; Snoha, D.J.

1985-05-01

A unique X-ray diffraction instrument for residual stress measurement has been developed that provides for speed, ease of measurement, accuracy, and economy of surface stress measurement. Application of this instrument with a material removal technique, e.g., electropolishing, has facilitated detailed, high resolution studies of three-dimensional stress fields. This paper describes the instrumentation and techniques applied to conduct the residual stress measurement and presents maps of the residual stress data obtained for the surfaces of a heavy 21/4 Cr 1 Mo steel plate weldment.

20. Thermoluminescent dosimeters for low dose X-ray measurements.

PubMed

Fernández, S Del Sol; García-Salcedo, R; Sánchez-Guzmán, D; Ramírez-Rodríguez, G; Gaona, E; de León-Alfaro, M A; Rivera-Montalvo, T

2016-01-01

The response of TLD-100, CaSO4:Dy and LiF:Mg,Cu,P for a range of X-ray low dose was measured. For calibration, the TLDs were arranged at the center of the X-ray field. The dose output of the X-ray machine was determined using an ACCU-Gold. All dosimeters were exposed at the available air kerma values of 14.69 mGy within a field 10×10 cm(2) at 80 cm of SSD. Results of LiF:Mg,Cu,P X-ray irradiated showed 4.8 times higher sensitivity than TLD-100. Meanwhile, TL response of CaSO4:Dy exposed at the same dose was 5.6 time higher than TLD-100. Experimental results show for low dose X-ray measurements a better linearity for LiF:Mg,Cu,P compared with that of TLD-100. CaSO4:Dy showed a linearity from 0.1 to 60 mGy. PMID:26609683

1. Radiation measurements around X-ray cabinet systems.

PubMed

Suric Mihic, M; Vucic, Z; Prlic, I; Lulic, I; Mestrovic, T

2012-07-01

Security personnel who operate X-ray units for the control of hand luggage and personal items at airports are generally not under dosimetric surveillance. A significant increase in the number of inspected items per passenger, due to rigorous air traffic security measures, raises a question of extended exposure of these workers to scattered X-ray radiation. A new approach to investigating directions of breaches of scattered X-ray radiation in the area near to an X-ray cabinet system, which is based on using active electronic dosemeters is presented. Influence of the increase in the number of inspected items in time on the dose rate is described. Time-dependent dose rates have showed a very good correlation with passengers undergoing security control prior to boarding an airplane. Measurements confirmed that an increase in the dose rate, coinciding with rush hours, was caused by scattered radiation passing through incompletely closed lead curtains. It is found that the doses at the entrance to the inspection tunnel are 50% higher than those at the exit, which is a consequence of inherent operational characteristics of X-ray cabinet systems. PMID:22302108

2. In-flight measurements of Terrestrial Gamma-Rays

van Deursen, Alexander; Kochkin, Pavlo; de Boer, Alte; Bardet, Michiel; Boissin, Jean-Francois

2014-05-01

Thunderstorms emit bursts of energetic radiation. Moreover, lightning stepped leader produces X-ray pulses. The phenomena, their interrelation and impact on Earth's atmosphere and near space are not fully understood yet. In-flight Lightning Strike Damage Assessment System ILDAS is developed in a EU FP6 project ( http://ildas.nlr.nl/ ) to provide information on threat that lightning poses to aircraft. It consists of 2 E-field sensors, and a varying number of H-field sensors. It has recently been modified to include two LaBr3 scintillation detectors. The scintillation detectors are sensitive to x- and gamma-rays above 30 keV. The entire system is installed on A-350 aircraft and digitizes data with 100 MSamples/sec rate when triggered by lightning. A continuously monitoring channel counts the number of occurrences that the X-ray signal exceeds a set of trigger levels. In the beginning of 2014 the aircraft flies through thunderstorm cells collecting the data from the sensors. The X-rays generated by the lightning flash are measured in synchronization with the lightning current information during a period of 1 second around the strike. The continuous channel stores x-ray information with less time and amplitude resolution during the whole flight. That would allow x-rays from TGFs and continuous gamma-ray glow of thundercloud outside that 1 s time window. We will give an overview of the ILDAS system and show that the X-ray detection works as intended. The availability of the lightning associated data depends on the flight schedule. If available, these data will be discussed at the conference.

3. Results from the LADCP measurements conducted in the Eurasian Arctic

Goszczko, Ilona; Pnyushkov, Andrey; Polyakov, Igor; Rember, Robert; Thurnherr, Andreas M.

2015-04-01

Preliminary results from 114 dual headed LADCP (Lowered Acoustic Doppler Current Profiler) measurements performed during the NABOS (Nansen and Amundsen Basin Observational System) 2013 cruise in the Eurasian Basin of the Arctic Ocean are discussed. Calculated horizontal magnetic field strength for that specific study area and cruise time span equals to 1500-4200 nT which is a critically low value. This affected the heading usability of instruments' compasses, thereby making the obtained ocean currents velocities and directions difficult to assess. Additional data post-processing performed with the LDEO Software (Version IX_9) and dedicated Matlab routines have so far allowed to obtain reasonable velocity profiles only in several cases (with additional information from the SeaBird 911plus CTD, GPS and bottom tracking). Thus, doubts concerning the feasibility of compasses, confirmed by difficulties encountered previously in similar polar locations, rise the necessity of providing an additional heading source which should be mounted together with the Teledyne RDI instruments to gain an unquestionable velocity field.

4. CT scanner x-ray spectrum estimation from transmission measurements

PubMed Central

Duan, Xinhui; Wang, Jia; Yu, Lifeng; Leng, Shuai; McCollough, Cynthia H.

2011-01-01

Purpose: In diagnostic CT imaging, multiple important applications depend on the knowledge of the x-ray spectrum, including Monte Carlo dose calculations and dual-energy material decomposition analysis. Due to the high photon flux involved, it is difficult to directly measure spectra from the x-ray tube of a CT scanner. One potential method for indirect measurement involves estimating the spectrum from transmission measurements. The expectation maximization (EM) method is an accurate and robust method to solve this problem. In this article, this method was evaluated in a commercial CT scanner. Methods: Two step-wedges (polycarbonate and aluminum) were used to produce different attenuation levels. Transmission measurements were performed on the scanner and the measured data from the scanner were exported to an external computer to calculate the spectra. The EM method was applied to solve the equations that represent the attenuation processes of polychromatic x-ray photons. Estimated spectra were compared to the spectra simulated using a software provided by the manufacturer of the scanner. To test the accuracy of the spectra, a verification experiment was performed using a phantom containing different depths of water. The measured transmission data were compared to the transmission values calculated using the estimated spectra. Results: Spectra of 80, 100, 120, and 140 kVp from a dual-source CT scanner were estimated. The estimated and simulated spectra were well matched. The differences of mean energies were less than 1 keV. In the verification experiment, the measured and calculated transmission values were in excellent agreement. Conclusions: Spectrum estimation using transmission data and the EM method is a quantitatively accurate and robust technique to estimate the spectrum of a CT system. This method could benefit studies relying on accurate knowledge of the x-ray spectra from CT scanner. PMID:21452736

5. Measurements of the hard-x-ray reflectivity of iridium

SciTech Connect

Romaine, S.; Bruni, R.; Gorenstein, P.; Zhong, Z

2007-01-10

In connection with the design of a hard-x-ray telescope for the Constellation X-Ray Observatory we measured the reflectivity of an iridium-coated zerodur substrate as a function of angle at 55, 60, 70, and 80 keV at the National Synchrotron Light Source of Brookhaven National Laboratory. The optical constants were derived from the reflectivity data. The real component of the index of refraction is in excellent agreement with theoretical values at all four energies. However, the imaginary component, which is related to the mass attenuation coefficient, is 50% to 70% larger at 55, 60, and 70 keV than theoretical values.

6. Measurement of the energy of horizontal cosmic ray muons

Gettert, Michael

1993-03-01

An experiment in which the energy of cosmic ray muons is determined by measuring the electron positron pairs that they radiate off when passing through matter is described. The detector is a stack of lead converters interspersed with ionization chambers for particle detection. The chambers use as active medium the liquid tetra methyl silane (TMS). The radiated quanta initiate electromagnetic cascades in the lead and are recognized due to the characteristic shower development. The energy spectrum of horizontal muons is presented and from this the primary cosmic ray spectrum is deduced.

7. A COMPARISON OF GADRAS SIMULATED AND MEASURED GAMMA RAY SPECTRA

SciTech Connect

Jeffcoat, R.; Salaymeh, S.

2010-06-28

Gamma-ray radiation detection systems are continuously being developed and improved for detecting the presence of radioactive material and for identifying isotopes present. Gamma-ray spectra, from many different isotopes and in different types and thicknesses of attenuation material and matrixes, are needed to evaluate the performance of these devices. Recently, a test and evaluation exercise was performed by the Savannah River National Laboratory that required a large number of gamma-ray spectra. Simulated spectra were used for a major portion of the testing in order to provide a pool of data large enough for the results to be statistically significant. The test data set was comprised of two types of data, measured and simulated. The measured data were acquired with a hand-held Radioisotope Identification Device (RIID) and simulated spectra were created using Gamma Detector Response and Analysis Software (GADRAS, Mitchell and Mattingly, Sandia National Laboratory). GADRAS uses a one-dimensional discrete ordinate calculation to simulate gamma-ray spectra. The measured and simulated spectra have been analyzed and compared. This paper will discuss the results of the comparison and offer explanations for spectral differences.

8. Miniature pulsed magnet system for synchrotron x-ray measurements

SciTech Connect

Linden, Peter J. E. M. van der; Mathon, Olivier; Strohm, Cornelius; Sikora, Marcin

2008-07-15

We have developed a versatile experimental apparatus for synchrotron x-ray measurements in pulsed high magnetic fields. The apparatus consists of a double cryostat incorporating a liquid nitrogen bath to cool the miniature pulsed coil and an independent helium flow cryostat allowing sample temperatures from 4 up to 250 K. The high duty cycle miniature pulsed coils can generate up to 38 T. During experiments at 30 T a repetition rate of 6 pulses/min was routinely reached. Using a 4 kJ power supply, the pulse duration was between 500 {mu}s and 1 ms. The setup was used for nuclear forward scattering measurements on {sup 57}Fe up to 25 T on the ESRF beamline ID18. In another experiment, x-ray magnetic circular dichroism was measured up to 30 T on the ESRF energy dispersive beamline ID24.

9. Measuring x-ray spectra of flash radiographic sources

Gehring, Amanda E.; Espy, Michelle A.; Haines, Todd J.; Mendez, Jacob; Moir, David C.; Sedillo, Robert; Shurter, Roger P.; Volegov, Petr; Webb, Timothy J.

2015-08-01

A Compton spectrometer has been re-commissioned for measurements of flash radiographic sources. The determination of the energy spectrum of these sources is difficult due to the high count rates and short nature of the pulses (~50 ns). The spectrometer is a 300 kg neodymium-iron magnet which measures spectra in the <1 MeV to 20 MeV energy range. Incoming x-rays are collimated into a narrow beam incident on a converter foil. The ejected Compton electrons are collimated so that the forward-directed electrons enter the magnetic field region of the spectrometer. The position of the electrons at the magnet's focal plane is a function of their momentum, allowing the x-ray spectrum to be reconstructed. Recent measurements of flash sources are presented.

10. Atmospheric measurements at Mars via gamma ray spectroscopy

NASA Technical Reports Server (NTRS)

Metzger, Albert E.; Haines, Eldon L.

1990-01-01

This paper describes three methods for measuring the Martian atmosphere using gamma ray spectroscopy. One method determines atmospheric thickness based on the energy-dependent differential attenuation of gamma-ray line pairs from a common element. Another makes a direct determination based on measurements of the line flux generated in the atmosphere, requires knowledge of the concentration of the component being used. The third, which makes use of a single line emitted from the surface where its flux can be established. The effects of stratigraphy on the differential attenuation method are studied, and calculations are reported which show that the measurement of atmospheric argon will be a sensitive indicator of the atmospheric fractionation accompanying CO2 precipitation in south polar regions.

11. Precision measurement of cosmic-Ray antiproton spectrum

PubMed

Orito; Maeno; Matsunaga; Abe; Anraku; Asaoka; Fujikawa; Imori; Ishino; Makida; Matsui; Matsumoto; Mitchell; Mitsui; Moiseev; Motoki; Nishimura; Nozaki; Ormes; Saeki; Sanuki; Sasaki; Seo; Shikaze; Sonoda; Streitmatter

2000-02-01

The energy spectrum of cosmic-ray antiprotons ( &pmacr;'s) has been measured in the range 0.18-3.56 GeV, based on 458 &pmacr;'s collected by BESS in a recent solar-minimum period. We have detected for the first time a characteristic peak at 2 GeV of &pmacr;'s originating from cosmic-ray interactions with the interstellar gas. The peak spectrum is reproduced by theoretical calculations, implying that the propagation models are basically correct and that different cosmic-ray species undergo a universal propagation. Future BESS data with still higher statistics will allow us to study the solar modulation and the propagation in detail and to search for primary &pmacr; components. PMID:11017448

12. X-ray Spectral Measurements of a Dense Plasma Focus

Whitlock, Robert R.; Dozier, Charles M.; Newman, Daniel A.; Petr, Rodney A.; Freshman, Jay; Hoey, David W.; Heaton, John

2002-10-01

Absolute intensities of spectra in a dense-plasma-focus (DPF) source have been recorded and analyzed. This DPF source has been identified as one of the more promising sources for X-ray lithography. The source, developed by Science Research Laboratory, Inc., is currently undergoing testing and further development at BAE Systems, Inc. The DPF operates at 60 Hz and produces an average output pulse of ~5 J of X rays into 4π steradians in a continuous operation mode. In all runs, there was an initial number of pulses, typically between 30 to 40, during which the X-ray output increased and the DPF appeared to be undergoing a conditioning process, and after which a "steady-state" mode was achieved where the average X-ray power was relatively constant. Each spectral run was exposed to ~600 J of output, as measured by the PIN. The X-ray spectral region between 0.8 and 3 keV was recorded on Kodak DEF film in a potassium acid phthalate (KAP) convex curved-crystal spectrograph. The source emits neon line radiation from Ne IX and Ne X ionization stages in the 900 to 1300 eV region, suitable for lithographic exposures of photoresist. Two helium-like neon lines contribute more than 50% of the total energy. From continuum shape, plasma temperatures were found to be approximately 170-200 eV. The absolute, integrated spectral outputs were verified to within 30% by comparison with measurements by a PIN detector and a radiachromic X-ray dosimeter.

13. Venus Measurements by the MESSENGER Gamma-Ray and X-Ray Spectrometers

Rhodes, E. A.; Starr, R. D.; Goldsten, J. O.; Schlemm, C. E.; Boynton, W. V.

2007-12-01

The Gamma-Ray Spectrometer (GRS), which is a part of the Gamma-Ray and Neutron Spectrometer Instrument, and the X-Ray Spectrometer (XRS) on the MESSENGER spacecraft made calibration measurements during the Venus flyby on June 5, 2007. The purpose of these instruments is to determine elemental abundances on the surface of Mercury. The GRS measures gamma-rays emitted from element interactions with cosmic rays impinging on the surface, while the XRS measures X-ray emissions induced on the surface by the incident solar flux. The GRS sensor is a high-resolution high-purity Ge detector cooled by a Stirling cryocooler, surrounded by a borated-plastic anticoincidence shield. The GRS is sensitive to gamma-rays up to ~10 MeV and can identify most major elements, sampling down to depths of about ten centimeters. Only the shield was powered on for this flyby in order to conserve cooler lifetime. Gamma-rays were observed coming from Venus as well as from the spacecraft. Although the Venus gamma-rays originate from its thick atmosphere rather than its surface, the GRS data from this encounter will provide useful calibration data from a source of known composition. In particular, the data will be useful for determining GRS sensitivity and pointing options for the Mercury flybys, the first of which will be in January 2008. The X-ray spectrum of a planetary surface is dominated by a combination of the fluorescence and scattered solar X-rays. The most prominent fluorescent lines are the Kα lines from the major elements Mg, Al, Si, S, Ca, Ti, and Fe (1-10 keV). The sampling depth is less than 100 u m. The XRS is similar in design to experiments flown on Apollo 15 and 16 and the NEAR-Shoemaker mission. Three large-area gas-proportional counters view the planet, and a small Si-PIN detector mounted on the spacecraft sunshade monitors the Sun. The energy resolution of the gas proportional counters (~850 eV at 5.9 keV) is sufficient to resolve the X-ray lines above 2 keV, but Al and Mg

14. FLUXEN portable equipment for direct X-ray spectra measurements

Aiello, S.; Bottigli, U.; Fauci, F.; Golosio, B.; Lo Presti, D.; Masala, G. L.; Oliva, P.; Raso, G.; Stumbo, S.; Tangaro, S.

2004-02-01

The proper use of imaging equipment in radiological units is based on an appropriate knowledge of the physical characteristics of the X-ray beam used. The FLUXEN PROJECT is working on a portable apparatus which, together with dedicated software, is able to perform an exact spectral reconstruction of the radiation produced in diagnostic X-ray tubes. The apparatus characterizes the energy spectrum of radiological tubes and also provides a measurement of the emitted flux. The acquisition system is based on a commercial CZT detector (3×3×2 mm 3), produced by AMPTEK, cooled by a Peltier cell, with a high efficiency in the diagnostic X-ray energy range and modified in the shaping electronics so as to obtain a faster response. The acquiring section lies on a NuDAQ I/O card with a sampling frequency of up to 20 MHz. The signal produced by the X-ray tube is wholly acquired and an off-line analysis is made so as to make possible an accurate recognition of pile-up events and a reconstruction of the emitted spectra. The reconstructed spectra of a General Electric Senographe DMR mammographic X-ray tube are shown.

15. X-ray power and yield measurements at the refurbished Z machine

SciTech Connect

Jones, M. C. Ampleford, D. J.; Cuneo, M. E.; Hohlfelder, R.; Jennings, C. A.; Johnson, D. W.; Jones, B.; Lopez, M. R.; MacArthur, J.; Mills, J. A.; Preston, T.; Rochau, G. A.; Savage, M.; Spencer, D.; Sinars, D. B.; Porter, J. L.

2014-08-15

Advancements have been made in the diagnostic techniques to measure accurately the total radiated x-ray yield and power from z-pinch implosion experiments at the Z machine with high accuracy. The Z machine is capable of outputting 2 MJ and 330 TW of x-ray yield and power, and accurately measuring these quantities is imperative. We will describe work over the past several years which include the development of new diagnostics, improvements to existing diagnostics, and implementation of automated data analysis routines. A set of experiments on the Z machine were conducted in which the load and machine configuration were held constant. During this shot series, it was observed that the total z-pinch x-ray emission power determined from the two common techniques for inferring the x-ray power, a Kimfol filtered x-ray diode diagnostic and the total power and energy diagnostic, gave 449 TW and 323 TW, respectively. Our analysis shows the latter to be the more accurate interpretation. More broadly, the comparison demonstrates the necessity to consider spectral response and field of view when inferring x-ray powers from z-pinch sources.

16. Neutron and Gamma Ray Scattering Measurements for Subsurface Geochemistry

Ellis, Darwin V.

1990-10-01

Developed for the oil industry, well logging instrumentation based on electrical, acoustic, and nuclear measurements has been providing information about the localization and evaluation of hydrocarbon-bearing strata for petroleum geologists and engineers since 1927. This method of exploring properties of the earth's crust without taking physical samples is attracting a growing audience of geologists and geophysicists because of recent developments that permit nondestructive measurements of subsurface geochemistry. A combination of nuclear measurement techniques, which use gamma ray and neutron sources, can provide detailed information on rock composition of interest to both industry and academia.

17. Spatially localized measurement of thermal conductivity using a hybrid photothermal technique

SciTech Connect

David H Hurley; Marat Khafizov; Zilong Hua; Rory Kennedy; Heng Ban

2012-05-01

A photothermal technique capable of measuring thermal conductivity with micrometer lateral resolution is presented. This technique involves measuring separately the thermal diffusivity, D, and thermal effusivity, e, to extract the thermal conductivity, k=(e2/D)1/2. To generalize this approach, sensitivity analysis was conducted for materials having a range of thermal conductivities. Experimental validation was sought using two substrate materials, SiO2 and CaF2, both coated with thin titanium films. The measured conductivities compare favorably with literature values.

18. A large detector for cosmic ray abundance and energy measurements

Alsop, C.

A large aperture, balloon borne cosmic ray detector was designed to measure the energy spectra of individual cosmic ray species with Z greater than 8 in the energy range 0.3GeV/N to 400GeV/N. The energy dependence of the abundance spectrum extending up to such high energies will provide valuable data for determining the nature of the origin and propagation of cosmic rays in the Galaxy. The properties of cosmic ray nuclei and the interpretation of the energy dependence of the abundance spectrum are discussed. The design and response of the BUGS IV cosmic ray detector are described. The measurement techniques used are gas scintillation, gas proportional scintillation and Cerenkov radiation from both gases and solids. The light collection properties of the detector and several experimental investigations of the light collection efficiency of the drift chamber region are described. The expected signals from the gas scintillation and gas Cerenkov emissions are predicted and the choice of a suitable scintillating gas mixture for minimizing the uncertainty in the charge and energy measurements is considered. The theoretical aspects of electron drift and diffusion in gases and several experimental investigations on the electron drift in the BUGS IV drift chamber are given. Also some preliminary results from a uniform field drift chamber are included which demonstrate the sensitivity of the electron drift velocity in inert gas mixtures to water vapor contamination. The expected overall performance of BUGS IV and the results of an experimental simulation of the parachute landing of the detector are given.

19. Gamma-ray backscatter for body composition measurement.

PubMed

Morgan, H M; Shakeshaft, J T; Lillicrap, S C

1998-01-01

The purpose of this study was to examine the potential of using backscatter information to assess regional body composition at selected sites. Two measurement techniques are examined: the measurement of the ratio of coherent to Compton scatter, and the measurement of the Compton scatter profile. Two possible applications are considered: the measurement of trabecular bone mineral density, and the measurement of the average fat/muscle ratio in a tissue volume. The results presented indicate that the analysis of coherent and Compton backscattered gamma-ray spectra from an 241Am source has the potential for measuring both trabecular bone mineral density and average fat/muscle ratio in a tissue volume, with a low absorbed dose to the subject. PMID:9569541

20. Gamma Ray Burst 150518a measured at different wavelengths

Apala, Ellizabeth Ann; Soderberg, Alicia Margarita; West, Michael

2016-01-01

Gamma Ray Burst (GRB's), extremely energetic flashes of Gamma Rays, are caused by either deaths of massive unstable stars or colliding binary neutron stars. A unique burst, GRB 150518a, had two recorded bursts fifteen minutes apart which is very rare and is considered to be ultra-long, lasting around thirty minutes total and is associated with a Supernova explosion. GBR 150518a is also extremely close compared to the average burst being measured to have a redshift of .2, this is important to note because GRB's measuring less than a redshift of .3 only are seen every ten years. Gamma rays are emitted by supernovae, neutron stars, black holes, and quasars and by studying GRB's it allows us to see more deeply into how these objects function. The first few days of GRB 150518as' detected afterglow was plotted in different wavelengths, including optical, x-ray, radio, and infrared, in flux verses time. Data is continuously being added as time goes on. This research is funded by the NSF, grant number 1358990.

1. Measuring X-ray Spectra of Flash Radiographic Sources

Gehring, Amanda; Espy, Michelle; Haines, Todd; Mendez, Jacob; Moir, David; Sedillo, Robert; Volegov, Petr; Webb, Tim

2015-10-01

A Compton spectrometer has been re-commissioned for measurements of flash radiographic sources. The determination of the energy spectrum provides information about the x-ray production mechanisms of these sources (ie. reaction history of plasmas, electron-target interactions) and benefits the analysis of images obtained at radiographic facilities. However, the measurements of the spectra are difficult due to the high count rates and short nature of the pulses (~ 50 ns). The spectrometer is a 300 kg neodymium-iron magnet which measures spectra in the <1 MeV to 20 MeV energy range. Incoming x-rays are collimated into a narrow beam incident on a converter foil. The ejected Compton electrons are collimated so that the forward-directed electrons enter the magnetic field region of the spectrometer. The position of the electrons at the focal plane of the magnet is a function of their momentum, allowing the x-ray spectrum to be reconstructed. Recent measurements of both flash and continuous radiographic sources will be presented.

2. Strain measurements in aluminum interconnects by x-ray microdiffraction

Hwang, Keith J.

2000-10-01

Reliability of metal interconnects in integrated circuits is a major concern to the microelectronics industry. Understanding the impact of stress and strain in metal lines is crucial for improving their reliability. Because of thermal expansion mismatches between the interconnect, substrate, and passivation material, high tensile stresses are developed during processing. In addition, stress gradients develop due to electromigration because of the high current densities passing through the lines. X-ray diffraction is an ideal technique for directly measuring these stresses. However, most of the earlier measurements were performed using millimeter size x-ray beams, allowing only macroscopic determinations of stress. Spatially resolved measurements of stresses in interconnects were not possible. A synchrotron-based white beam x-ray microdiffraction technique was developed and applied for localized strain mapping on polycrystalline thin film interconnects. The system was shown to achieve micron-scale spatial resolution and strain sensitivities on the order of 2 x 10-4. Two methods for performing in-situ calibration of the detector angles utilizing the (001) silicon substrate were presented: the energy method and the interplanar angle method. Various (hkl) reflections were measured from the (001) silicon substrate and the displacement of the x-ray beam was determined. Although discrepancies arose between these methods, both proved satisfactory to correct the Al (hkl) d-spacing measurements. Thermal and electromigration-induced hydrostatic stress distributions in a 2.6 mum wide passivated A1 line were investigated. The Al line exhibited thermal stress behavior consistent with confinement by the silicon/silicon dioxide interface. The electromigration-induced stress evolution indicated the presence of bamboo grains acting as blocking boundaries.

3. Dynamic force microscopy and x-ray photoemission spectroscopy studies of conducting polymer thin film on nanoscale structured Al surface

Kato, Hitoshi; Takemura, Susumu; Ishii, Atsuro; Takarai, Yoshiyuki; Watanabe, Yohei; Sugiyama, Takeharu; Hiramatsu, Tomoyasu; Nanba, Noriyuki; Nishikawa, Osamu; Taniguchi, Masahiro

2007-09-01

A nanoscale linked-crater structure was fabricated on an Al surface by chemical and electrochemical combination processes. The surface of an Al plate was treated with Semi Clean and was successively processed in anodization in H IISO 4. Dynamic force microscopy image (DFM) showed that a linked-crater structure was formed on the Al surface. At the next stage, the authors conducted the thin film growth of conducting polymer polythiophene on the Al surface by an electrochemical method. The electrochemical polymerization on the Al surface was performed in acetonitrile containing thiophene monomer and (Et) 4NBF 4 as a supporting electrolyte. After being electrochemically processed, the contour image of each crater was still recognized implying that the polymer nanofilm was grown on the nanoscale structured Al surface. The cross section analysis demonstrated that the nanofilm was grown along the linked-crater structure because the contour of each crater became thick. X-ray photoemission spectroscopy measurement also supported the polymer nanofilm growth because C 1s and S 2p lines were detected. Furthermore, copper phthalocyanine (CuPc) molecules are injected into the polymer nanofilm grown on the nanoscale structured Al surface by diffusing method in order to functionalize the nanoscale hybrid material.

4. Measuring TeV Cosmic-Ray Electrons with CREST

Schubnell, M.; Bower, C.; Coutu, S.; DuVernois, M.; McKee, S.; Muller, D.; Musser, J.; Nutter, S.; Swordy, S.; Tarle, G.; Tomasch, A.; Yagi, A.

2004-08-01

There is strong indirect evidence for the supernova shock acceleration of galactic cosmic-ray electrons through observations of non-thermal X-rays and TeV gamma rays from supernova remnants (SNRs). Current and past electron detectors, typically flown by high altitude balloons, have been limited in their ability to study high energy electrons in the local cosmic-ray flux by their short exposure times and small apertures. To date, no measurements have been made at energies greater than 2 TeV. Yet the detection of high-energy electrons would be extremely significant, yielding information about the spatial distribution of nearby cosmic ray sources. High-energy electrons lose energy rapidly during propagation in the Galaxy through synchrotron and inverse Compton processes and thus TeV electrons reaching the solar system have to originate at distances < 1 kpc, leaving few known supernova remnants from which these particles could originate. The spectral shape of high-energy electrons should, therefore, be strongly affected by the number of nearby sources, and their distance distribution. Conversely, if no such features in the high-energy electron spectrum are observed it will call into question our understanding of cosmic ray sources and propagation. The balloon-borne Cosmic Ray Electron Synchrotron Telescope (CREST) will detect high-energy electrons by measuring the X-ray synchrotron photons generated by these electrons in the Earth's magnetic field. This technique results in a substantial increase in the acceptance and sensitivity of the apparatus compared to the traditional direct detection of electrons. The instrument will consist of a 2m x 2m array of BGO crystals. Simulation studies indicate that with an ultra-long duration (100 day) flight, as many as 250 such electrons will be detected with energies greater than 2 TeV, with an expected background of only 1 event. A prototype instrument is currently being developed and will be flown in 2005 on a conventional

5. Recent cosmic-ray antiproton measurements and astrophysical implications

NASA Technical Reports Server (NTRS)

Buffington, A.; Schindler, S. M.

1981-01-01

Cosmic-ray antiprotons have been detected by a new balloon-borne experiment which covers the energy range between 130 and 320 MeV. Fourteen detected events yield a measured flux of 1.7 plus or minus 0.5 x 10 to the -4th antiprotons/sq m sr s MeV. The corresponding antiproton/proton ratio is 2.2 plus or minus 0.6 x 10 to the -4th, only slightly smaller than the ratio observed by other experiments at higher energies. The measured flux is significantly larger than predicted, and some cosmic-ray models which could explain this result are discussed.

6. Measurement of Solid Rocket Propellant Burning Rate Using X-ray Imaging

Denny, Matthew D.

The burning rate of solid propellants can be difficult to measure for unusual burning surface geometries, but X-ray imaging can be used to measure burning rate. The objectives of this work were to measure the baseline burning rate of an electrically-controlled solid propellant (ESP) formulation with real-time X-ray radiography and to determine the uncertainty of the measurements. Two edge detection algorithms were written to track the burning surface in X-ray videos. The edge detection algorithms were informed by intensity profiles of simulated 2-D X-ray images. With a 95% confidence level, the burning rates measured by the Projected-Slope Intersection algorithm in the two combustion experiments conducted were 0.0839 in/s +/-2.86% at an average pressure of 407 psi +/-3.6% and 0.0882 in/s +/-3.04% at 410 psi +/-3.9%. The uncertainty percentages were based on the statistics of a Monte Carlo analysis on burning rate.

7. Measurement and simulation of cosmic rays effects on neutron multiplicity counting

Weinmann-Smith, R.; Swinhoe, M. T.; Hendricks, J.

2016-04-01

Neutron coincidence and multiplicity counting is a standard technique used to measure uranium and plutonium masses in unknown samples for nuclear safeguards purposes, but background sources of radiation can obscure the results. In particular, high energy cosmic rays can produce large coincidence count contributions. Since some of the events occur in the sample itself, it is impossible to measure the background separately. This effect greatly increases the limit of detection of some low level neutron coincidence counting applications. The cosmic ray capability of MCNP6 was used to calculate the expected coincidence rates from cosmic rays for different sample configurations and experimental measurements were conducted for comparison. Uranium enriched to 66%, lead bricks, and an empty detector were measured in the mini Epithermal Neutron Multiplicity Counter, and MCNP6 simulations were made of the same measurements. The results show that the capability is adequate for predicting the expected background rates. Additional verification of MCNP6 was given by comparison of particle production rates to other publications, increasing confidence in MCNP6's use as a tool to lower the limit of detection. MCNP6 was then used to find particle and source information that would be difficult to detect experimentally. The coincidence count contribution was broken down by particle type for singles, doubles, and triples rates. The coincidence count contribution was broken down by source, from(a , n) , spontaneous fission, and cosmic rays, for each multiplicity.

8. Specific features of the luminescence and conductivity of zinc selenide on exposure to X-ray and optical excitation

SciTech Connect

Degoda, V. Ya. Sofienko, A. O.

2010-05-15

The set of experimental data on the X-ray-excited luminescence and X-ray induced conductivity of ZnSe are compared to the data on the photoluminescence and photoconductivity. It is experimentally established that the current-voltage characteristics and the kinetics of phosphorescence and current relaxation depend on the type of excitation. It is found that the external electric field influences the intensity and shape of bands in the luminescence spectra. It is shown that the character of excitation defines the kinetics of recombination, charge carrier trapping, and conductivity in wide-gap semiconductors.

9. Earth formation density measurement from natural gamma ray spectral logs

SciTech Connect

Smith Jr., H. D.

1985-07-02

Naturally occurring gamma radiations from earth formations in the vicinity of a well borehole are detected and spectrally separated into six energy regions or bands. Borehole compensation techniques are applied to the gamma ray spectra and the attenuation coefficient /eta/ is determined as a result thereof. The attenuation coefficient is used along with predetermined borehole, casing and cement parameters to derive a measure of the density of the earth formations.

10. Conductance method for the measurement of cross-sectional areas of the aorta.

PubMed

Kornet, L; Jansen, J R; Gussenhoven, E J; Hardeman, M R; Hoeks, A P; Versprille, A

1999-01-01

A modified conductance method to determine the cross-sectional areas (CSAs) of arteries in piglets was evaluated in vivo. The method utilized a conductance catheter having four electrodes. Between the outer electrodes an alternating current was applied and between the inner electrodes the induced voltage difference was measured and converted into a conductance. CSA was determined from measured conductance minus parallel conductance, which is the conductance of the tissues surrounding the vessel times the length between the measuring electrodes of the conductance catheter divided by the conductivity of blood. The parallel conductance was determined by injecting hypertonic saline to change blood conductivity. The conductivity of blood was calculated from temperature and hematocrit and corrected for maximal deformation and changes in orientation of the erythrocytes under shear stress conditions. The equations to calculate the conductivity of blood were obtained from in vitro experiments. In vivo average aortic CSAs. determined with the conductance method CSA(G) in five piglets, were compared to those determined with the intravascular ultrasound method CSA(IVUS). The regression equation between both values was CSA(G)=-0.09+1.00 x CSA(IVUS), r=0.97, n=53. The mean difference between the values was -0.29%+/-5.57% (2 standard deviations). We conclude that the modified conductance method is a reliable technique to estimate the average cross-sectional areas of the aorta in piglets. PMID:10199690

11. Efficiency of energy and protein deposition in swine measured by dual energy X-ray absorptiometry (DXA)

Technology Transfer Automated Retrieval System (TEKTRAN)

A series of studies were conducted using dual energy X-ray absorptiometry (DXA) to measure energy and protein deposition in pigs. In an initial validation study DXA was compared directly with slaughter analysis as a method for measuring body composition and energy deposition in pigs. Mean values fo...

12. X-ray measurement of magnetoelastic strain in epitaxial Er

Durfee, C. S.; Conover, M. J.; Flynn, C. P.

1997-03-01

Magnetic transitions are frequently accompanied by magnetoelastic distortions of the crystal lattice. In the case of epitaxially-grown thin magnetic films, however, distortions of the unit cell are potentially restricted by the clamping of the film to the substrate. In thicker epitaxial films (≈ 0.5 μ m), we expect that a film will not be rigidly clamped but will allow dislocations to absorb the lattice mismatch with the substrate. A thick epitaxial magnetic film in this limit offers a system to study dislocation formation and motion in the presence of a tunable field-induced mismatch between film and substrate. For this study, we have prepared strain-free Er films on sapphire by well-known MBE techniques, and have investigated magnetoelastic distortions using x-ray diffraction. X-ray measurements were performed using specially-constructed 40 kOe magnet dewar with x-ray windows. In-plane and perpendicular lattice parameters were measured at several applied magnetic fields, which allow the degree of clamping in the constrained direction to be directly measured. These strains will be discussed in the context of dislocation motion to accommodate lattice mismatch.

13. EGAF: Measurement and Analysis of Gamma-ray Cross Sections

Firestone, R. B.; Abusaleem, K.; Basunia, M. S.; Bečvář, F.; Belgya, T.; Bernstein, L. A.; Choi, H. D.; Escher, J. E.; Genreith, C.; Hurst, A. M.; Krtička, M.; Renne, P. R.; Révay, Zs.; Rogers, A. M.; Rossbach, M.; Siem, S.; Sleaford, B.; Summers, N. C.; Szentmiklosi, L.; van Bibber, K.; Wiedeking, M.

2014-05-01

The Evaluated Gamma-ray Activation File (EGAF) is the result of a 2000-2007 IAEA Coordinated Research Project to develop a database of thermal, prompt γ-ray cross sections, σγ, for all elemental and selected radioactive targets. No previous database of this kind had existed. EGAF was originally based on measurements using guided neutron beams from the Budapest Reactor on all elemental targets from Z=1-82, 90 and 92, except for He and Pm. The EGAF σγ data were published in the Database of Prompt Gamma Rays from Slow Neutron Capture for Elemental Analysis [1]. An international collaboration has formed to continue the EGAF measurements with isotopically enriched targets, derive total radiative thermal neutron cross sections, σ0, extend the σγ data from thermal to 20 MeV neutrons, compile a completed activation data file, improve sections of the Reference Input Parameter Library (RIPL) with more complete and up to date level and γ-ray data, evaluate statistical γ-ray data from reaction studies, and determine recommended neutron separations energies, Sn, for atomic mass evaluations. A new guided neutron beam facility has become available at the Garching (Munich) FRM II Reactor, and high energy neutron experimental facilities are being developed by a Berkeley area collaboration where 5-33 MeV neutron beams are available at the LBNL 88” cyclotron, 2.5 and 14 MeV beams at the University of California, Berkeley neutron generator laboratory, and high flux, 10 nṡcmṡ-2 s-1, neutron pulses available from the LLNL National Ignition Facility (NIF).

14. Analysis of variance on thickness and electrical conductivity measurements of carbon nanotube thin films

Li, Min-Yang; Yang, Mingchia; Vargas, Emily; Neff, Kyle; Vanli, Arda; Liang, Richard

2016-09-01

One of the major challenges towards controlling the transfer of electrical and mechanical properties of nanotubes into nanocomposites is the lack of adequate measurement systems to quantify the variations in bulk properties while the nanotubes were used as the reinforcement material. In this study, we conducted one-way analysis of variance (ANOVA) on thickness and conductivity measurements. By analyzing the data collected from both experienced and inexperienced operators, we found some operation details users might overlook that resulted in variations, since conductivity measurements of CNT thin films are very sensitive to thickness measurements. In addition, we demonstrated how issues in measurements damaged samples and limited the number of replications resulting in large variations in the electrical conductivity measurement results. Based on this study, we proposed a faster, more reliable approach to measure the thickness of CNT thin films that operators can follow to make these measurement processes less dependent on operator skills.

15. Measurement of the kaonic hydrogen x-ray spectrum.

PubMed

Beer, G; Bragadireanu, A M; Cargnelli, M; Curceanu-Petrascu, C; Egger, J-P; Fuhrmann, H; Guaraldo, C; Iliescu, M; Ishiwatari, T; Itahashi, K; Iwasaki, M; Kienle, P; Koike, T; Lauss, B; Lucherini, V; Ludhova, L; Marton, J; Mulhauser, F; Ponta, T; Schaller, L A; Seki, R; Sirghi, D L; Sirghi, F; Zmeskal, J

2005-06-01

The DEAR (DAPhiNE exotic atom research) experiment measured the energy of x rays emitted in the transitions to the ground state of kaonic hydrogen. The measured values for the shift epsilon and the width Gamma of the 1s state due to the K(-)p strong interaction are epsilon(1s)=-193 +/- 37 (stat) +/- 6 (syst) eV and Gamma(1s)=249 +/- 111 (stat) +/- 30 (syst) eV, the most precise values yet obtained. The pattern of the kaonic hydrogen K-series lines, K(alpha), K(beta), and K(gamma), was disentangled for the first time. PMID:16090312

16. Measurement of the Kaonic Hydrogen X-Ray Spectrum

Beer, G.; Bragadireanu, A. M.; Cargnelli, M.; Curceanu-Petrascu, C.; Egger, J.-P.; Fuhrmann, H.; Guaraldo, C.; Iliescu, M.; Ishiwatari, T.; Itahashi, K.; Iwasaki, M.; Kienle, P.; Koike, T.; Lauss, B.; Lucherini, V.; Ludhova, L.; Marton, J.; Mulhauser, F.; Ponta, T.; Schaller, L. A.; Seki, R.; Sirghi, D. L.; Sirghi, F.; Zmeskal, J.

2005-06-01

The DEAR (DAΦNE exotic atom research) experiment measured the energy of x rays emitted in the transitions to the ground state of kaonic hydrogen. The measured values for the shift ɛ and the width Γ of the 1s state due to the K-p strong interaction are ɛ1s=-193±37 (stat) ±6 (syst) eV and Γ1s=249±111 (stat) ±30 (syst) eV, the most precise values yet obtained. The pattern of the kaonic hydrogen K-series lines, Kα, Kβ, and Kγ, was disentangled for the first time.

17. Use of tandem circulation wells to measure hydraulic conductivity without groundwater extraction.

PubMed

Goltz, Mark N; Huang, Junqi; Close, Murray E; Flintoft, Mark J; Pang, Liping

2008-09-10

Conventional methods to measure the hydraulic conductivity of an aquifer on a relatively large scale (10-100 m) require extraction of significant quantities of groundwater. This can be expensive, and otherwise problematic, when investigating a contaminated aquifer. In this study, innovative approaches that make use of tandem circulation wells to measure hydraulic conductivity are proposed. These approaches measure conductivity on a relatively large scale, but do not require extraction of groundwater. Two basic approaches for using circulation wells to measure hydraulic conductivity are presented; one approach is based upon the dipole-flow test method, while the other approach relies on a tracer test to measure the flow of water between two recirculating wells. The approaches are tested in a relatively homogeneous and isotropic artificial aquifer, where the conductivities measured by both approaches are compared to each other and to the previously measured hydraulic conductivity of the aquifer. It was shown that both approaches have the potential to accurately measure horizontal and vertical hydraulic conductivity for a relatively large subsurface volume without the need to pump groundwater to the surface. Future work is recommended to evaluate the ability of these tandem circulation wells to accurately measure hydraulic conductivity when anisotropy and heterogeneity are greater than in the artificial aquifer used for these studies. PMID:18674844

18. Temperature and emission measure from GOES soft X-ray measurements

Garcia, Howard A.

1994-10-01

This paper provides a detailed description of the procedure used for computing color temperature and emission measure from Geostationary Operational Environmental Satellite (GOES) X-ray data, including a table of constants for Synchronous Meteorological Satellite (SMS) and GOES X-ray sensors that are necessary for reducing the archived data from these satellites. Temperature and theoretical current tables were constructed, for individual GOES sensors, from laboratory calibrations of instrument responses and from synthetic solar X-ray spectra generated by two models of solar thermal X-ray emission: Raymond-Smith and Mewe-Alkemade. Example tables are shown and others are available on request. Errors that may be incurred from the use of GOES X-ray data in the computation of flare temperatures and emission measures may be classified under four major groups: instrument induced errors, including errors of calibration and random measurements errors; environmentally induced errors, due primarily to the ambient energetic electron background; solar influences, including the consequences of the isothermal assumption and the single-source assumption; and uncertainties in the modelled solar synthetic spectrum. These error sources are discussed separately, and a rough estimation of the collective error is made where this is quantitatively feasible. Finally, temperatures and emission measures are computed from GOES data and are compared with those derived from Solar Maximum Mission (SMM) and Hinotori soft X-ray spectrometer data and from broadband photometric data from the PROGNOZ satellite.

19. Measurements of Si hybrid CMOS x-ray detector characteristics

Bongiorno, Stephen D.; Falcone, Abraham D.; Burrows, David N.; Cook, Robert

2010-07-01

20. Simultaneous measurement of electrical conductance and thermopower of single benzenedithiol molecular junctions

Kaneko, Satoshi; Nakamura, Yuuga; Matsushita, Ryuuji; Marqués-González, Santiago; Kiguchi, Manabu

2015-06-01

We have developed a system for the simultaneous measurement of electrical conductance and thermopower of the single benzenedithiol (BDT) molecular junction, which was characterized by inelastic electron tunneling spectroscopy, at low temperature. The simultaneous measurements revealed a negative correlation between the electrical conductance and the thermopower. Strong metal-molecule coupling at the single BDT molecular junction leads to high conductance and low thermopower because of the broadening of the conduction orbital, which explains the negative correlation. The observed fluctuation in conductance and thermopower reflects the change in the metal-molecule contact configuration and molecular orientation.

1. Gamma-ray scattering for fat fraction measurement.

PubMed

Shakeshaft, J; Morgan, H M; Lillicrap, S C

1997-07-01

The work reported examines the potential of using gamma-ray photon backscatter information to measure in vivo the percentage of fat in specific tissue volumes. 241Am gamma rays are used as the source and the backscatter detected with a hyperpure germanium detector, with ethanol (approximately 80% fat, 20% muscle) and water (muscle) being used as tissue substitutes. Two measurement techniques are examined; the measurement of the ratio of coherent scatter to Compton scatter and the measurement of the Compton scatter profile. Both are shown to be sensitive to the composition difference between ethanol and water. For the coherent-Compton scatter ratio, the measured difference between water and ethanol is 1.85:1, close to the value calculated (about 2:1). A similar difference in the coherent-Compton ratios between muscle and fat is calculated (2.2:1). The FWHM of the Compton profile has also been shown to vary with tissue composition with a difference of 0.10 keV (5%) between the ethanol and water profile widths. PMID:9253048

2. Gamma-ray scattering for fat fraction measurement

Shakeshaft, J.; Morgan, H. M.; Lillicrap, S. C.

1997-07-01

The work reported examines the potential of using gamma-ray photon backscatter information to measure in vivo the percentage of fat in specific tissue volumes. gamma rays are used as the source and the backscatter detected with a hyperpure germanium detector, with ethanol (approximately 80% fat, 20% muscle) and water (muscle) being used as tissue substitutes. Two measurement techniques are examined; the measurement of the ratio of coherent scatter to Compton scatter and the measurement of the Compton scatter profile. Both are shown to be sensitive to the composition difference between ethanol and water. For the coherent - Compton scatter ratio, the measured difference between water and ethanol is 1.85:1, close to the value calculated (about 2:1). A similar difference in the coherent - Compton ratios between muscle and fat is calculated (2.2:1). The FWHM of the Compton profile has also been shown to vary with tissue composition with a difference of 0.10 keV (5%) between the ethanol and water profile widths.

3. Lorentz force sigmometry: a novel technique for measuring the electrical conductivity of solid and liquid metals

Alkhalil, Shatha; Kolesnikov, Yurii; Thess, André

2015-11-01

In this paper, a novel method to measure the electrical conductivity of solid and molten metals is described. We term the method ‘Lorentz force sigmometry’, where the term ‘sigmometry’ refers to the letter sigma σ, often used to denote the electrical conductivity. The Lorentz force sigmometry method is based on the phenomenon of eddy currents generation in a moving conductor exposed to a magnetic field. Based on Ampere’s law, the eddy currents in turn generate a secondary magnetic field; as a result, the Lorentz force acts to brake the conductor. Owing to Newton’s third law, a measurable force, which is equal to the Lorentz force and is directly proportional to the electrical conductivity of the conductive fluid or solid, acts on the magnet. We present the results of the measurements performed on solids along with the initial measurements on fluids with a eutectic alloy composition of Ga67In20.5Sn12.5; detailed measurements on molten metals are still in progress and will be published in the future. We conducted a series of experiments and measured the properties of known electrical conductive metals, including aluminum and copper, to compute the calibration factor of the device, and then used the same calibration factor to estimate the unknown electrical conductivity of a brass bar. The predicted electrical conductivity of the brass bar was compared with the conductivity measured with a commercial device called ‘SigmaTest’ the observed error was less than 0.5%.

4. FPGA-Based X-Ray Detection and Measurement for an X-Ray Polarimeter

NASA Technical Reports Server (NTRS)

Gregory, Kyle; Hill, Joanne; Black, Kevin; Baumgartner, Wayne

2013-01-01

This technology enables detection and measurement of x-rays in an x-ray polarimeter using a field-programmable gate array (FPGA). The technology was developed for the Gravitational and Extreme Magnetism Small Explorer (GEMS) mission. It performs precision energy and timing measurements, as well as rejection of non-x-ray events. It enables the GEMS polarimeter to detect precisely when an event has taken place so that additional measurements can be made. The technology also enables this function to be performed in an FPGA using limited resources so that mass and power can be minimized while reliability for a space application is maximized and precise real-time operation is achieved. This design requires a low-noise, charge-sensitive preamplifier; a highspeed analog to digital converter (ADC); and an x-ray detector with a cathode terminal. It functions by computing a sum of differences for time-samples whose difference exceeds a programmable threshold. A state machine advances through states as a programmable number of consecutive samples exceeds or fails to exceed this threshold. The pulse height is recorded as the accumulated sum. The track length is also measured based on the time from the start to the end of accumulation. For track lengths longer than a certain length, the algorithm estimates the barycenter of charge deposit by comparing the accumulator value at the midpoint to the final accumulator value. The design also employs a number of techniques for rejecting background events. This innovation enables the function to be performed in space where it can operate autonomously with a rapid response time. This implementation combines advantages of computing system-based approaches with those of pure analog approaches. The result is an implementation that is highly reliable, performs in real-time, rejects background events, and consumes minimal power.

5. Measurement of soil moisture with cosmic-ray neutrons in deciduous forests

Heidbüchel, Ingo; Blume, Theresa; Güntner, Andreas

2014-05-01

In deciduous forests the calibration of cosmic-ray soil moisture sensors is difficult since the amount of water stored inside and on vegetation (leaves, branches, stems) varies seasonally. A one-time calibration conducted during summer can therefore introduce errors to the method that are especially pronounced in the winter season. We performed calibration in a deciduous forest at the TERENO observatory in north-eastern Germany at different times throughout the year to capture the changing influence of water in the vegetation on the calibration results. Additionally, we calibrated the cosmic-ray neutron sensor with soil samples from different soil depths (0-10 cm, 0-20 cm, 0-30 cm). We compared the resulting soil moisture time series with time series of FDR-based soil moisture point measurements at different depths. This allows us to estimate the error introduced by the influence of organic layers at the soil surface (litter, decomposed organic material) which can vary temporally. The same sensor setup was also used to look at time-lags between the cosmic-ray soil moisture signal and measurements of precipitation, intercepted water and soil moisture point measurements at different depths. Recorded time lags between point measurements and cosmic-ray soil moisture results can potentially help in tracking precipitation on its way through the canopy, the organic layer and into the soils.

6. Diffuse Galactic Continuum Gamma Rays. A Model Compatible with EGRET Data and Cosmic-ray Measurements

NASA Technical Reports Server (NTRS)

Strong, Andrew W.; Moskalenko, Igor V.; Reimer, Olaf

2004-01-01

We present a study of the compatibility of some current models of the diffuse Galactic continuum gamma-rays with EGRET data. A set of regions sampling the whole sky is chosen to provide a comprehensive range of tests. The range of EGRET data used is extended to 100 GeV. The models are computed with our GALPROP cosmic-ray propagation and gamma-ray production code. We confirm that the "conventional model" based on the locally observed electron and nucleon spectra is inadequate, for all sky regions. A conventional model plus hard sources in the inner Galaxy is also inadequate, since this cannot explain the GeV excess away from the Galactic plane. Models with a hard electron injection spectrum are inconsistent with the local spectrum even considering the expected fluctuations; they are also inconsistent with the EGRET data above 10 GeV. We present a new model which fits the spectrum in all sky regions adequately. Secondary antiproton data were used to fix the Galactic average proton spectrum, while the electron spectrum is adjusted using the spectrum of diffuse emission it- self. The derived electron and proton spectra are compatible with those measured locally considering fluctuations due to energy losses, propagation, or possibly de- tails of Galactic structure. This model requires a much less dramatic variation in the electron spectrum than models with a hard electron injection spectrum, and moreover it fits the y-ray spectrum better and to the highest EGRET energies. It gives a good representation of the latitude distribution of the y-ray emission from the plane to the poles, and of the longitude distribution. We show that secondary positrons and electrons make an essential contribution to Galactic diffuse y-ray emission.

7. Recent results from cosmic-ray measurements with LOFAR

Schellart, P.; Buitink, S.; Corstanje, A.; Enriquez, J. E.; Falcke, H.; Frieswijk, W.; Hörandel, J. R.; Krause, M.; Nelles, A.; Scholten, O.; ter Veen, S.; Thoudam, S.; van den Akker, M.

2014-04-01

LOFAR, the Low Frequency Array, is currently the world's largest distributed radio telescope observing at frequencies below 240 MHz. LOFAR is measuring cosmic-ray induced air-showers since June 2011 and has collected several hundreds of events with hundreds of antennas per individual event. We present measurements of the radio signal strength as well as high-precision measurements of wavefront curvature and polarization. These will enable us to disentangle the different emission mechanisms at play, such as geomagnetic radiation, charge excess, and Askaryan or Cherenkov effects, leading to a full understanding of the air-shower radio emission. Furthermore we give a first example on how the full complexity of the signal enables radio measurements to be used to study primary particle composition.

8. Guide to plutonium isotopic measurements using gamma-ray spectrometry

SciTech Connect

Lemming, J.F.; Rakel, D.A.

1982-08-26

Purpose of this guide is to assist those responsible for plutonium isotopic measurements in the application of gamma-ray spectrometry. Objectives are to promote an understanding of the measurement process, including its limitations and applicability, by reviewing the general features of a plutonium spectrum and identifying the quantities which must be extracted from the data; to introduce state-of-the-art analysis techniques by reviewing four isotopic analysis packages and identifying their differences; to establish the basis for measurement control and assurance by discussing means of authenticating the performance of a measurement system; and to prepare for some specific problems encountered in plutonium isotopic analyses by providing solutions from the practical experiences of several laboratories. 29 references, 12 figures, 17 tables.

9. Apparatus and method for detecting and/or measuring flaws in conductive material

DOEpatents

Hockey, Ronald L.; Riechers, Douglas M.

2000-01-01

The present invention uses a magnet and sensor coil unilaterial and in relative motion to a conductive material, to measure perturbation or variation in the magnetic field in the presence of a flaw. A liftoff compensator measures a distance between the conductive material and the magnet.

10. X-ray power and yield measurements at the refurbished Z machine

SciTech Connect

Jones, M. C.; Ampleford, D. J.; Cuneo, M. E.; Hohlfelder, R.; Jennings, C. A.; Johnson, D. W.; Jones, B.; Lopez, M. R.; MacArthur, J.; Mills, J. A.; Preston, T.; Rochau, G. A.; Savage, M.; Spencer, D.; Sinars, D. B.; Porter, J. L.

2014-08-04

Advancements have been made in the diagnostic techniques to measure accurately the total radiated x-ray yield and power from z-pinch loads at the Z Machine with high accuracy. The Z-accelerator is capable of outputting 2MJ and 330 TW of x-ray yield and power, and accurately measuring these quantities is imperative. We will describe work over the past several years which include the development of new diagnostics, improvements to existing diagnostics, and implementation of automated data analysis routines. A set of experiments were conducted on the Z machine where the load and machine configuration were held constant. During this shot series, it was observed that total z-pinch x-ray emission power determined from the two common techniques for inferring the x-ray power, Kimfol filtered x-ray diode diagnostic and the Total Power and Energy diagnostic gave 450 TW and 327 TW respectively. Our analysis shows the latter to be the more accurate interpretation. More broadly, the comparison demonstrates the necessity to consider spectral response and field of view when inferring xray powers from z-pinch sources.

11. X-ray power and yield measurements at the refurbished Z machine

DOE PAGESBeta

Jones, M. C.; Ampleford, D. J.; Cuneo, M. E.; Hohlfelder, R.; Jennings, C. A.; Johnson, D. W.; Jones, B.; Lopez, M. R.; MacArthur, J.; Mills, J. A.; et al

2014-08-04

Advancements have been made in the diagnostic techniques to measure accurately the total radiated x-ray yield and power from z-pinch loads at the Z Machine with high accuracy. The Z-accelerator is capable of outputting 2MJ and 330 TW of x-ray yield and power, and accurately measuring these quantities is imperative. We will describe work over the past several years which include the development of new diagnostics, improvements to existing diagnostics, and implementation of automated data analysis routines. A set of experiments were conducted on the Z machine where the load and machine configuration were held constant. During this shot series,more » it was observed that total z-pinch x-ray emission power determined from the two common techniques for inferring the x-ray power, Kimfol filtered x-ray diode diagnostic and the Total Power and Energy diagnostic gave 450 TW and 327 TW respectively. Our analysis shows the latter to be the more accurate interpretation. More broadly, the comparison demonstrates the necessity to consider spectral response and field of view when inferring xray powers from z-pinch sources.« less

12. A new measurement of kaonic hydrogen X-rays

Siddharta Collaboration; Bazzi, M.; Beer, G.; Bombelli, L.; Bragadireanu, A. M.; Cargnelli, M.; Corradi, G.; Curceanu (Petrascu), C.; D'Uffizi, A.; Fiorini, C.; Frizzi, T.; Ghio, F.; Girolami, B.; Guaraldo, C.; Hayano, R. S.; Iliescu, M.; Ishiwatari, T.; Iwasaki, M.; Kienle, P.; Levi Sandri, P.; Longoni, A.; Lucherini, V.; Marton, J.; Okada, S.; Pietreanu, D.; Ponta, T.; Rizzo, A.; Romero Vidal, A.; Scordo, A.; Shi, H.; Sirghi, D. L.; Sirghi, F.; Tatsuno, H.; Tudorache, A.; Tudorache, V.; Vazquez Doce, O.; Widmann, E.; Zmeskal, J.

2011-10-01

The K¯N system at threshold is a sensitive testing ground for low energy QCD, especially for the explicit chiral symmetry breaking. Therefore, we have measured the K-series X-rays of kaonic hydrogen atoms at the DAΦNE electron-positron collider of Laboratori Nazionali di Frascati, and have determined the most precise values of the strong-interaction energy-level shift and width of the 1s atomic state. As X-ray detectors, we used large-area silicon drift detectors having excellent energy and timing resolution, which were developed especially for the SIDDHARTA experiment. The shift and width were determined to be ɛ1s=-283±36(stat)±6(syst) eV and Γ1s=541±89(stat)±22(syst) eV, respectively. The new values will provide vital constraints on the theoretical description of the low-energy K¯N interaction.

13. Measurements of ultraheavy cosmic rays with HEAO-3

NASA Technical Reports Server (NTRS)

Binns, W. R.; Israel, M. H.; Klarmann, J.; Garrard, T. L.; Stone, E. C.; Waddington, C. J.

1987-01-01

The HEAO-3 Heavy Nuclei Experiment has measured abundances of elements from Ar-18 to U-92 in the cosmic rays. The results on the ultraheavy elements, those with atomic numbers greater than 30, indicate that the source of the cosmic rays contain a mixture of r-process and s-process material similar to that found in the solar system. This result is at variance with previous indications that the sources are greatly enhanced with freshly synthesized r-process material. Apparent discrepancies between the results and the accepted solar-system abundance have led to a reexamination of data on photospheric abundances of Ge and Pb, resulting in suggested reductions in their values.

14. Measuring and interpreting X-ray fluorescence from planetary surfaces.

PubMed

Owens, Alan; Beckhoff, Burkhard; Fraser, George; Kolbe, Michael; Krumrey, Michael; Mantero, Alfonso; Mantler, Michael; Peacock, Anthony; Pia, Maria-Grazia; Pullan, Derek; Schneider, Uwe G; Ulm, Gerhard

2008-11-15

As part of a comprehensive study of X-ray emission from planetary surfaces and in particular the planet Mercury, we have measured fluorescent radiation from a number of planetary analog rock samples using monochromatized synchrotron radiation provided by the BESSY II electron storage ring. The experiments were carried out using a purpose built X-ray fluorescence (XRF) spectrometer chamber developed by the Physikalisch-Technische Bundesanstalt, Germany's national metrology institute. The XRF instrumentation is absolutely calibrated and allows for reference-free quantitation of rock sample composition, taking into account secondary photon- and electron-induced enhancement effects. The fluorescence data, in turn, have been used to validate a planetary fluorescence simulation tool based on the GEANT4 transport code. This simulation can be used as a mission analysis tool to predict the time-dependent orbital XRF spectral distributions from planetary surfaces throughout the mapping phase. PMID:18855420

15. Isotopic stack - measurement of heavy cosmic ray isotopes

NASA Technical Reports Server (NTRS)

Beaujean, R.

1981-01-01

Heavy cosmic ray nuclei with nuclear charge, Z, equal to or greater than 3 are to be measured using an isotopic stack consisting of passive visual track detectors which remain sensitive throughout the entire mission. The scientific data are stored in latent tracks which are produced by heavy ions and which can be revealed in the investigator's laboratory after recovery. During the mission, only housekeeping data have to be collected. The exposure onboard Spacelab 1 allows the study of the chemical composition and energy spectrum of articles which have energies in the range 20 to 100 million electron volts per atomic mass unit, as well as the isotopic composition of heavy galactic cosmic rays with energies in the range 100 to 1000 million electron volts per atomic mass unit.

16. Gamma-ray measurements of a 6-kilogram neptunium sphere

SciTech Connect

Moss, C. E.; Frankle, C. M.

2002-01-01

In order to better determine the properties of {sup 237}Np for criticality safety and nuclear nonproliferation, especially its critical mass, 6070-gram solid sphere was cast on 15 May 2001 in a hot cell. The casting sprue was cut off on a lathe and the casting ground to a final diameter of 8.29 cm. The sphere was enclosed in a spherical tungsten shell 0.523-cm thick to reduce the gamma-ray dose. The neptunium and the tungsten were doubly encapsulated in welded, spherical nickel shells, each 0.381-cm thick. The sprue material was analyzed by mass spectrometry. Here we report the results of the first gamma-ray measurements of this unique item.

17. Hydrodynamic Measurements of Bremsstrahlung Converter with X-ray Backlighting

Goldin, Fletcher; Caporaso, George; Chambers, Frank; Falabella, Steve; Guethlein, Gary; Ho, Darwin; McCarrick, James; Richardson, Roger; Sampayan, Steve; Trimble, Dave; Weir, John

2002-11-01

Performance of bremsstrahlung converters is under study using the 6 MeV, 2 kA, 50 ns electron beam produced by LLNL's Experimental Test Accelerator II. Critical for use in multi-pulse machines (e.g., DARHT-2) is the rate of target material expansion after e-beam heating (from the earlier pulses). Target designs are currently being developed using hydrodynamic calculations, but to verify our models, we directly measure density vs. time. A secondary X-ray source, with a pulse width (25 ns) short compared to target expansion timescale (1-10 ms) probes the target, and the fraction of X-rays transmitted implies an integrated material density at that time. Marching through various relative delay times in a sequence of shots then maps the rate of density decrease. Experimental technique will be discussed, and results will be compared to numerical simulation. Work performed for USDOE by UC/LLNL under contract W-7405-ENG-48.

18. CALET: a calorimeter for cosmic-ray measurements in space

Mori, Nicola

2013-06-01

The CALorimetric Electron Telescope (CALET) instrument is scheduled for a launch in 2014 and attached to the Exposed Facility of the Japanese Experimental Module (JEM-EF) on the International Space Station. Its main objective is to perform precise measurements of the electron+positron spectrum in cosmic rays at energies up to some TeV, searching for signals from dark matter and/or contributions from nearby astrophysical sources like pulsars. Other scientific goals include the investigation of heavy ions spectra up to Fe, elemental abundance of trans-iron nuclei and a measurement of the diffuse γ ray emission with high energy resolution. The instrument is now under construction, and consists of a charge detection device (CHD) composed of two layers of plastic scintillators, a finely-segmented sampling calorimeter (IMC) and a deep, homogeneous calorimeter (TASC) made of PbWO scintillating bars. The good containment of electromagnetic showers (total depth ˜3X0(IMC)+27X0(TASC)=30X0) together with the homogeneity of TASC give an energy resolution for electrons and γ rays about 2%. CHD can discriminate the charge of primary particles with a resolution between 15% and 30% up to Fe. The finely-segmented IMC, made by tungsten layers and 1mm-wide scintillating fibers, can provide detailed information about the start and early development of particle showers. Lateral and longitudinal shower-development information from TASC, together with informations from IMC, can be used to achieve an electron/proton rejection power about 105. High-statistics for collected data will be achieved by means of the planned 5-years exposure time together with a geometrical factor of 0.12 m sr. Furthermore, a Gamma-Ray Burst monitor will complement the main detector. In this paper the status of the mission, the design and expected performance of the instrument will be detailed.

19. System for absolute measurement of electrolytic conductivity in aqueous solutions based on van der Pauw's theory

Zhang, Bing; Lin, Zhen; Zhang, Xiao; Yu, Xiang; Wei, Jiali; Wang, Xiaoping

2014-05-01

Based on an innovative application of van der Pauw's theory, a system was developed for the absolute measurement of electrolytic conductivity in aqueous solutions. An electrolytic conductivity meter was designed that uses a four-electrode system with an axial-radial two-dimensional adjustment structure coupled to an ac voltage excitation source and signal collecting circuit. The measurement accuracy, resolution and repeatability of the measurement system were examined through a series of experiments. Moreover, the measurement system and a high-precision electrolytic conductivity meter were compared using some actual water samples.

20. Performance characteristics of high-conductivity channel electron multipliers. [as UV and x ray detector

NASA Technical Reports Server (NTRS)

Timothy, J. G.; Bybee, R. L.

1978-01-01

The paper describes a new type of continuous channel multiplier (CEM) fabricated from a low-resistance glass to produce a high-conductivity channel section and thereby obtain a high count-rate capability. The flat-cone cathode configuration of the CEM is specifically designed for the detection of astigmatic exit images from grazing-incidence spectrometers at the optimum angle of illumination for high detection efficiencies at XUV wavelengths. Typical operating voltages are in the range of 2500-2900 V with stable counting plateau slopes in the range 3-6% per 100-V increment. The modal gain at 2800 V was typically in the range (50-80) million. The modal gain falls off at count rates in excess of about 20,000 per sec. The detection efficiency remains essentially constant to count rates in excess of 2 million per sec. Higher detection efficiencies (better than 20%) are obtained by coating the CEM with MgF2. In life tests of coated CEMs, no measurable change in detection efficiency was measured to a total accumulated signal of 2 times 10 to the 11th power counts.

1. Measurement of the thermal properties of electrically conducting fluids using coated transient hot wires

SciTech Connect

Perkins, R.A.

1994-12-31

Measurements of fluid thermal properties using the transient hot-wire technique are described. When bare hot wires are used in electrically conducting fluids there are additional measurement uncertainties due to the formation of electric double layers on the surfaces of the wires and the cell wall. If the electrical conductivity of the fluid is large enough there is also significant power generation in the fluid. These measurement uncertainties can be eliminated by electrically insulating the hot wires with a thin film. The use of tantalum hot wires with an anodized layer of tantalum pentoxide is demonstrated with measurements on nonpolar argon and polar 1,1,1,2 tetrafluoroethane (R134a). Although coated tantalum hot wires have been used previously in a transient mode to measure the thermal conductivity of liquids, this work is the first demonstration of the use of coated wires to measure thermal conductivity in the liquid, vapor, and supercritical gas phases.

2. Measurement of the thermal properties of electrically conducting fluids using coated transient hot wires

SciTech Connect

Perkins, R.A.

1994-09-01

Measurements of fluid thermal properties using the transient hot-wire technique are described. When bare hot wires are used in electrically conducting fluids there are additional measurement uncertainties due to the formation of electric double layers on the surfaces of the wires and the cell wall. If the electrical conductivity of the fluid is large enough there is also significant power generation in the fluid. These measurement uncertainties can be eliminated by electrically insulating the hot wires with a thin film. The use of tantalum hot wires with an anodized layer of tantalum pentoxide is demonstrated with measurements on nonpolar argon and polar 1,1,1,2 tetrafluorethane (R134a). Although coated tantalum hot wires have been used previously in a transient mode to measure the thermal conductivity of liquids, this work is the first demonstration of the use of coated wires to measure thermal conductivity in the liquid, vapor, and supercritical gas phases.

3. Development of an in situ thermal conductivity measurement system for exploration of the shallow subsurface

Chirila, Marian Andrei; Christoph, Benjamin; Vienken, Thomas; Dietrich, Peter; Bumberger, Jan

2016-06-01

In this study, we attempted to develop an in situ thermal conductivity measurement system that can be used for subsurface thermal exploration. A new thermal probe was developed for mapping both the spatial and temporal variability of thermal conductivity, via direct push methods in the unconsolidated shallow subsurface. A robust, hollow cylindrical probe was constructed and its performance was tested by carrying out thermal conductivity measurements on materials with known properties. The thermal conductivity of the investigated materials can be worked out by measuring the active power consumption (in alternating current system) and temperature of the probe over fixed time intervals. A calibration method was used to eliminate any undesired thermal effects regarding the size of the probe, based on mobile thermal analyzer thermal conductivity values. Using the hollow cylindrical probe, the thermal conductivity results obtained had an error of less than 2.5% for solid samples (such as Teflon, Agar Jelly and Nylatron).

4. Microbial growth and biofilm formation in geologic media is detected with complex conductivity measurements

Davis, Caroline A.; Atekwana, Estella; Atekwana, Eliot; Slater, Lee D.; Rossbach, Silvia; Mormile, Melanie R.

2006-09-01

Complex conductivity measurements (0.1-1000 Hz) were obtained from biostimulated sand-packed columns to investigate the effect of microbial growth and biofilm formation on the electrical properties of porous media. Microbial growth was verified by direct microbial counts, pH measurements, and environmental scanning electron microscope imaging. Peaks in imaginary (interfacial) conductivity in the biostimulated columns were coincident with peaks in the microbial cell concentrations extracted from sands. However, the real conductivity component showed no discernible relationship to microbial cell concentration. We suggest that the observed dynamic changes in the imaginary conductivity (σ″) arise from the growth and attachment of microbial cells and biofilms to sand surfaces. We conclude that complex conductivity techniques, specifically imaginary conductivity measurements are a proxy indicator for microbial growth and biofilm formation in porous media. Our results have implications for microbial enhanced oil recovery, CO2 sequestration, bioremediation, and astrobiology studies.

5. Sodium Concentration Measurement during Hemodialysis through Ion-Exchange Resin and Conductivity Measure Approach: In Vitro Experiments

PubMed Central

Tura, Andrea; Sbrignadello, Stefano; Mambelli, Emanuele; Ravazzani, Paolo; Santoro, Antonio; Pacini, Giovanni

2013-01-01

Sodium measurement during hemodialysis treatment is important to preserve the patient from clinical events related to hypo- or hyper-natremia Usually, sodium measurement is performed through laboratory equipment which is typically expensive, and requires manual intervention. We propose a new method, based on conductivity measurement after treatment of dialysate solution through ion-exchange resin. To test this method, we performed in vitro experiments. We prepared 40 ml sodium chloride (NaCl) samples at 280, 140, 70, 35, 17.5, 8.75, 4.375 mEq/l, and some “mixed samples”, i.e., with added potassium chloride (KCl) at different concentrations (4.375-17.5 mEq/l), to simulate the confounding factors in a conductivity-based sodium measurement. We measured the conductivity of all samples. Afterwards, each sample was treated for 1 min with 1 g of Dowex G-26 resin, and conductivity was measured again. On average, the difference in the conductivity between mixed samples and corresponding pure NaCl samples (at the same NaCl concentration) was 20.9%. After treatment with the exchange resin, it was 14.7%, i.e., 42% lower. Similar experiments were performed with calcium chloride and magnesium chloride as confounding factors, with similar results. We also performed some experiments on actual dialysate solution during hemodialysis sessions in 15 patients, and found that the correlation between conductivity measures and sodium concentration improved after resin treatment (R=0.839 before treatment, R=0.924 after treatment, P<0.0001). We conclude that ion-exchange resin treatment coupled with conductivity measures may improve the measurement of sodium compared to conductivity measures alone, and may become a possible simple approach for continuous and automatic sodium measurement during hemodialysis. PMID:23844253

6. Conductivity Measurements of Pyrrole Molecules Incorporated into Chemically Adsorbed Monolayer by Conducting Probe Technique in Atomic Force Microscope

Yamamoto, Shin‑ichi; Ogawa, Kazufumi

2006-03-01

A monomolecular layer containing pyrrolyl groups at the surface was prepared between two parallel Pt electrodes on a glass substrate by a chemical adsorption technique using N-[11-(trichlorosilyl)undecyl] pyrrole (PNN). Then, the pyrrolyl was polymerized with pure water by applying a DC voltage of 10 V between the two Pt electrodes. It was confirmed using an optical microscope that many electric paths were formed between the two Pt electrodes by a decoration technique using electrochemical polymerization in an aqueous medium containing pyrrole after the polymerization. Next, a conductive probe of an atomic force microscope (AFM) was used to examine an electrical polymerized path through the surface of the polypyrrolyl group in a chemically adsorbed monomolecular layer. The resistance of one electric path in the monomolecular layer was measured using an AFM with an attached Au-covered tip at room temperature. With a measurement volume of about 0.2 nm (the thickness of the electric path in the monomolecular layer) × 200 μm (the average width of the electric path) × 100 μm (the distance between the Pt electrode and the Au-covered AFM tip), the resistance at room temperature of one electric path was 4 k Ω under ambient conditions. From the results in the atmosphere, the conductivity of a super long conjugated polypyrrolyl group without any dopant in a lateral direction was ohmically estimated to be at least 6.0 × 105 S/m.

7. Predicted CALET Measurements of Ultra-Heavy Cosmic Ray Abundances

Rauch, Brian

2013-04-01

The CALorimetric Electron Telescope (CALET), comprised of main calorimeter telescope (CAL) and Gamma-ray Burst Monitor (CGBM), is under construction for launch to the ISS in 2014. CAL consists of a Charge Detector (CHD) with two segmented planes of 1 cm thick plastic scintillator, an Imaging Calorimeter (IMC) with a total of 3 radiation lengths (X0) of tungsten plates read out with 8 planes of interleaved scintillating fibers, and a Total Absorption Calorimeter (TASC) with 27 X0 of lead tungstate (PWO) logs. The primary objectives of CAL are to measure electron energy spectra from 1GeV to 20 TeV, to detect gamma-rays above 10 GeV, and to measure the energy spectra of nuclei from protons through iron up to 1,000 TeV. In this paper we discuss the predicted abundance measurements CAL can make of rare ultra-heavy (UH) nuclei (30 <=Z <=40). In addition to the nuclei that pass within the full CAL geometry, UH nuclei can be resolved using the CHD and top IMC layers without requiring particle energy determination in the TASC in the portion of the ISS 51.6^o inclination orbit where the geomagnetic rigidity cutoffs are above minimum ionization in the scintillator. In 5-years CAL would collect 4-5 times the UH statistics of TIGER.

8. Thermal contact conductance of spotwelded titanium joints - Measurements and a generalized analytical model

Flynn, Edward M.; Choi, Paul S.

1990-06-01

Measurements and an analytical investigation of the thermal contact conductance of spotwelded joints are presented. Pairs of .081-cm thick sheets of Ti-6Al-4V alloy were resistance welded to form test coupons representing skins and stiffeners. The spotweld number density was varied. Measurements of contact conductance of these coupons were made at temperatures from 120 to 232 C. In addition, a thermal model of the spotweld interface was constructed which yielded good predictions of spotweld conduction, gaseous conduction, and gap radiation.

9. Kaonic hydrogen X-ray measurement in SIDDHARTA

Bazzi, M.; Beer, G.; Bombelli, L.; Bragadireanu, A. M.; Cargnelli, M.; Corradi, G.; Curceanu (Petrascu), C.; D'Uffizi, A.; Fiorini, C.; Frizzi, T.; Ghio, F.; Guaraldo, C.; Hayano, R. S.; Iliescu, M.; Ishiwatari, T.; Iwasaki, M.; Kienle, P.; Levi Sandri, P.; Longoni, A.; Lucherini, V.; Marton, J.; Okada, S.; Pietreanu, D.; Ponta, T.; Rizzo, A.; Romero Vidal, A.; Scordo, A.; Shi, H.; Sirghi, D. L.; Sirghi, F.; Tatsuno, H.; Tudorache, A.; Tudorache, V.; Vazquez Doce, O.; Widmann, E.; Zmeskal, J.; Siddharta Collaboration

2012-05-01

Kaonic hydrogen atoms provide a unique laboratory to probe the kaon-nucleon strong interaction at the energy threshold, allowing an investigation of the interplay between spontaneous and explicit chiral symmetry breaking in low-energy QCD. The SIDDHARTA Collaboration has measured the K-series X rays of kaonic hydrogen atoms at the DAΦNE electron-positron collider of Laboratori Nazionali di Frascati, and has determined the most precise values of the strong-interaction induced shift and width of the 1s atomic energy level. This result provides vital constraints on the theoretical description of the low-energy K¯N interaction.

10. Muon multiplicities measured using an underground cosmic-ray array

Kuusiniemi, P.; Enqvist, T.; Bezrukov, L.; Fynbo, H.; Inzhechik, L.; Joutsenvaara, J.; Loo, K.; Lubsandorzhiev, B.; Petkov, V.; Slupecki, M.; Trzaska, W. H.; Virkajärvi, A.

2016-05-01

EMMA (Experiment with Multi-Muon Array) is an underground detector array designed for cosmic-ray composition studies around the knee energy (or ~ 1 — 10 PeV). It operates at the shallow depth in the Pyhasalmi mine, Finland. The array consists of eleven independent detector stations ~ 15 m2 each. Currently seven stations are connected to the DAQ and the rest will be connected within the next few months. EMMA will determine the multiplicity, the lateral density distribution and the arrival direction of high-energy muons event by event. The preliminary estimates concerning its performance together with an example of measured muon multiplicities are presented.

11. Local structure analysis of magnetic transparent conducting films by x-ray spectroscopy

Nakamura, Toshihiro

2016-02-01

We prepared Mn-doped indium-tin oxide (ITO) films on glass substrates by radio-frequency magnetron sputtering and investigated local structures surrounding Mn ions in the films by x-ray absorption spectroscopy. The Fourier transform of the extended x-ray absorption fine structure (EXAFS) spectrum indicated that the Mn ions preferably substitute the In ions at the b sites of the In2O3 lattice. According to the threshold energy obtained from the inflection point of the edge in the x-ray absorption near edge structure (XANES) spectrum, the valence of the Mn ions was evaluated to range from  +2 to  +3. These x-ray absorption spectroscopic data are useful for revealing the origin of the magnetism of the Mn-doped ITO films.

12. Perspectives of the GAMMA-400 space observatory for high-energy gamma rays and cosmic rays measurements

Topchiev, N. P.; Galper, A. M.; Bonvicini, V.; Adriani, O.; Aptekar, R. L.; Arkhangelskaja, I. V.; Arkhangelskiy, A. I.; Bakaldin, A. V.; Bergstrom, L.; Berti, E.; Bigongiari, G.; Bobkov, S. G.; Boezio, M.; Bogomolov, E. A.; Bonechi, S.; Bongi, M.; Bottai, S.; Castellini, G.; Cattaneo, P. W.; Cumani, P.; Dalkarov, O. D.; Dedenko, G. L.; De Donato, C.; Dogiel, V. A.; Finetti, N.; Gorbunov, M. S.; Gusakov, Yu V.; Hnatyk, B. I.; Kadilin, V. V.; Kaplin, V. A.; Kaplun, A. A.; Kheymits, M. D.; Korepanov, V. E.; Larsson, J.; Leonov, A. A.; Loginov, V. A.; Longo, F.; Maestro, P.; Marrocchesi, P. S.; Men'shenin, A. L.; Mikhailov, V. V.; Mocchiutti, E.; Moiseev, A. A.; Mori, N.; Moskalenko, I. V.; Naumov, P. Yu; Papini, P.; Pearce, M.; Picozza, P.; Rappoldi, A.; Ricciarini, S.; Runtso, M. F.; Ryde, F.; Serdin, O. V.; Sparvoli, R.; Spillantini, P.; Stozhkov, Yu I.; Suchkov, S. I.; Taraskin, A. A.; Tavani, M.; Tiberio, A.; Tyurin, E. M.; Ulanov, M. V.; Vacchi, A.; Vannuccini, E.; Vasilyev, G. I.; Yurkin, Yu T.; Zampa, N.; Zirakashvili, V. N.; Zverev, V. G.

2016-02-01

The GAMMA-400 gamma-ray telescope is intended to measure the fluxes of gamma-rays and cosmic-ray electrons and positrons in the energy range from 100 MeV to several TeV. Such measurements concern the following scientific tasks: investigation of point sources of gamma-rays, studies of the energy spectra of Galactic and extragalactic diffuse emission, studies of gamma-ray bursts and gamma-ray emission from the Sun, as well as high precision measurements of spectra of high-energy electrons and positrons. Also the GAMMA- 400 instrument provides the possibility for protons and nuclei measurements up to knee. But the main goal for the GAMMA-400 mission is to perform a sensitive search for signatures of dark matter particles in high-energy gamma-ray emission. To fulfill these measurements the GAMMA-400 gamma-ray telescope possesses unique physical characteristics in comparison with previous and present experiments. The major advantage of the GAMMA-400 instrument is excellent angular and energy resolution for gamma-rays above 10 GeV. The GAMMA-400 experiment will be installed onboard of the Navigator space platform, manufactured by the NPO Lavochkin Association. The expected orbit will be a highly elliptical orbit (with apogee 300.000 km and perigee 500 km) with 7 days orbital period. An important profit of such an orbit is the fact that the full sky coverage will always be available for gamma ray astronomy.

13. Thermal conductivity measurements of glass beads and regolith simulant under vacuum conditions

Sakatani, N.; Ogawa, K.; Iijima, Y.; Tsuda, S.; Honda, R.; Tanaka, S.

2013-09-01

Past studies of in-situ and laboratory measurements of lunar regolith thermal conductivity imply that the conductivity would vary with depth due to change of density and self-weighted stress. In this study, we experimentally investigated the effect of the compressional stress on the thermal conductivity of the glass beads and regolith simulant using a new stress controlling system under vacuum conditions. We experimentally confirmed that the thermal conductivity increases with the compressional stress, which indicates that the regolith layer on the airless terrestrial bodies has various thermal conductivities according to the depth and their gravity.

14. Length Dependent Thermal Conductivity Measurements Yield Phonon Mean Free Path Spectra in Nanostructures

PubMed Central

Zhang, Hang; Hua, Chengyun; Ding, Ding; Minnich, Austin J.

2015-01-01

Thermal conductivity measurements over variable lengths on nanostructures such as nanowires provide important information about the mean free paths (MFPs) of the phonons responsible for heat conduction. However, nearly all of these measurements have been interpreted using an average MFP even though phonons in many crystals possess a broad MFP spectrum. Here, we present a reconstruction method to obtain MFP spectra of nanostructures from variable-length thermal conductivity measurements. Using this method, we investigate recently reported length-dependent thermal conductivity measurements on SiGe alloy nanowires and suspended graphene ribbons. We find that the recent measurements on graphene imply that 70% of the heat in graphene is carried by phonons with MFPs longer than 1 micron. PMID:25764977

15. Length dependent thermal conductivity measurements yield phonon mean free path spectra in nanostructures.

PubMed

Zhang, Hang; Hua, Chengyun; Ding, Ding; Minnich, Austin J

2015-01-01

Thermal conductivity measurements over variable lengths on nanostructures such as nanowires provide important information about the mean free paths (MFPs) of the phonons responsible for heat conduction. However, nearly all of these measurements have been interpreted using an average MFP even though phonons in many crystals possess a broad MFP spectrum. Here, we present a reconstruction method to obtain MFP spectra of nanostructures from variable-length thermal conductivity measurements. Using this method, we investigate recently reported length-dependent thermal conductivity measurements on SiGe alloy nanowires and suspended graphene ribbons. We find that the recent measurements on graphene imply that 70% of the heat in graphene is carried by phonons with MFPs longer than 1 micron. PMID:25764977

16. Thermal conductivity measurements of particulate materials: 5. Effect of bulk density and particle shape

Presley, Marsha A.; Christensen, Philip R.

2010-07-01

Thermal conductivities were measured with a line-heat source for three particulate materials with different particle shapes under low pressures of a carbon dioxide atmosphere and various bulk densities. Less than 2 μm kaolinite exhibited a general decrease in thermal conductivity with increasing bulk density. For the range of atmospheric pressures appropriate for Mars, a reduction in porosity of 24% decreased the thermal conductivity by 24%. Kaolinite manifests considerable anisotropy with respect to thermal conductivity. As the particles align the bulk thermal conductivity measured increasingly reflects the thermal conductivity of the short axis. When kyanite is crushed, it forms blady particles that will also tend to align with increasing bulk density. Without any intrinsic anisotropy, however, kyanite particles, like other particulates exhibit an increase in thermal conductivity with increasing bulk density. Under Martian atmospheric pressures, a reduction in porosity of 30% produces a 30% increase in thermal conductivity. Diatomaceous earth maintains a very low bulk density due to the highly irregular shape of the individual particles. A decrease in porosity of 17% produces an increase in thermal conductivity of 27%. The trends in thermal conductivity with bulk density, whether increasing or decreasing, are often not smooth. Whether oscillations in the trends presented in this paper and elsewhere have any physical significance or whether they are merely artifacts of the precision error is unclear. Clarification of this question may not be possible without higher-precision measurements from future laboratories and further development of theoretical modeling.

17. Detecting Microbial Growth and Metabolism in Geologic Media with Complex Conductivity Measurements

Davis, C. A.; Atekwana, E. A.; Slater, L. D.; Bottrell, P. M.; Chasten, L. E.; Heidenreich, J. D.

2006-05-01

Complex conductivity measurements between 0.1-1000 Hz were obtained from biostimulated sand-packed (coarse and mixed fine and medium grain) columns to investigate microbial growth, biofilm formation, and microbial metabolism on the electrical properties of porous media. Microbial growth and metabolism was verified by direct microbial counts, pH changes, and environmental scanning electron microscope imaging. Peaks in imaginary (interfacial) conductivity in the coarse grain columns occurred concurrently with peaks in the microbial cell concentrations. The magnitude of the imaginary conductivity response in the mixed fine and medium grain columns, however, was low compared to the coarse grain sand columns, consistent with lower microbial cell concentrations. It is possible that the pore size in the mixed fine and medium grain sand restricted bacteria cell division, inhibiting microbial growth, and thus the smaller magnitude imaginary conductivity response. The biostimulated columns for both grain sizes displayed similar trends and showed an increase in the real (electrolytic) conductivity and decrease in pH over time. Dynamic changes in the imaginary conductivity arises from the growth and attachment of microbial cells and biofilms to surfaces, whereas, changes in the real conductivity arises from the release of byproducts (ionic species) of microbial metabolism. We conclude that complex conductivity techniques are feasible sensors for detecting microbial growth (imaginary conductivity measurements) and metabolism (real conductivity measurements) with implications for bioremediation and astrobiology studies.

18. On the Statistical Analysis of X-ray Polarization Measurements

NASA Technical Reports Server (NTRS)

Strohmayer, T. E.; Kallman, T. R.

2013-01-01

In many polarimetry applications, including observations in the X-ray band, the measurement of a polarization signal can be reduced to the detection and quantification of a deviation from uniformity of a distribution of measured angles of the form alpha plus beta cosine (exp 2)(phi - phi(sub 0) (0 (is) less than phi is less than pi). We explore the statistics of such polarization measurements using both Monte Carlo simulations as well as analytic calculations based on the appropriate probability distributions. We derive relations for the number of counts required to reach a given detection level (parameterized by beta the "number of sigma's" of the measurement) appropriate for measuring the modulation amplitude alpha by itself (single interesting parameter case) or jointly with the position angle phi (two interesting parameters case). We show that for the former case when the intrinsic amplitude is equal to the well known minimum detectable polarization (MDP) it is, on average, detected at the 3sigma level. For the latter case, when one requires a joint measurement at the same confidence level, then more counts are needed, by a factor of approximately equal to 2.2, than that required to achieve the MDP level. We find that the position angle uncertainty at 1sigma confidence is well described by the relation sigma(sub pi) equals 28.5(degrees) divided by beta.

19. Models for gamma-ray holdup measurements at duct contact

SciTech Connect

Sheppard, G.A.; Russo, P.A.; Wenz, T.R.; Miller, M.C.; Piquette, E.C. ); Haas, F.X.; Glick, J.B.; Garrett, A.G. )

1991-01-01

The use of gamma-ray measurements to nondestructively assay special nuclear material holdup in DOE processing facilities has increased recently. A measurement approach that is relatively insensitive to deposit geometry involves withdrawing the detector from the holdup-bearing equipment far enough to validate an assumed point-, line-, or area-source deposit geometry. Because of facility constraints, these generalized geometry procedures are not always followed, and some ducts are measured at contact. Quantitative interpretation of contact measurements requires knowledge of the width of the deposit transverse to the duct axis. Rocky Flats personnel have introduced a method to obtain data from which this width can be deduced. It involves taking measurements in pairs, with the detector viewing the holdup deposit at contact from above and below the duct. The interpretation of the top and bottom measurements to give the deposit width at each location requires a model for the detector's response to radial source position and a model for the deposit geometry. We have derived a relationship between the top-to-bottom count rate ratio and the deposit width that approximates the detector response and models the deposit geometry as a uniform strip. The model was validated in controlled experiments that used thin foils of high-enriched uranium metal to simulate duct deposits. 4 refs., 5 figs., 1 tab.

20. Measurement of soil saturated hydraulic conductivity: The method of constant pressure tubes

Technology Transfer Automated Retrieval System (TEKTRAN)

Field method to measure the saturated soil hydraulic conductivity is presented that does not require expensive equipment and preserves natural water flow pathways that may be bloked during soil core sampling for laboratory measurements. Vegetation must be removed from the plot prior the measurement...

1. On the van der Pauw's method applied to the measurement of low thermal conductivity materials

Morales, C.; Flores, E.; Bodega, J.; Leardini, F.; Ferrer, I. J.; Ares, J. R.; Sánchez, C.

2016-08-01

The electrical van der Pauw's method has recently been extended to measure the thermal conductivity of different elements and compounds. This technique provides an easy way to determine the sample in-plane thermal conductivity by avoiding the influence of the thermal contact resistances. However, the reported calculated error values appear to be underestimated when dealing with the materials with low thermal conductivity (<5 W/Km) at room temperature. The causes of this underestimation are investigated in this communication and it has been found that they are due to the drastic influence of conduction heat losses through the thermo-resistance wires as well as the resulting modification of the sample temperature map. Both phenomena lead to experimental values of the sample thermal conductivity, which are systematically higher than the tabulated ones. The magnitude of this systematic error is ˜100% dealing with the samples of macroscopic dimensions, and low thermal conductivity indicated that the obtained accurate measurements can be quite challenging.

2. Characterization Of Multilayer X-Ray Analyzers: Models And Measurements

Henke, B. L.; Uejio, J. Y.; Yamada, H. T.; Tackaberry, R. E.

1986-08-01

A procedure is described for a detailed characterization of multilayer analyzers that can be effectively applied to their design, optimization, and application for absolute x-ray spectrometry in the 100 to 10,000 eV photon energy region. An accurate analytical model has been developed that is based upon a simple modification of the dynamical Darwin-Prins theory to extend its application to finite multilayer systems and to the low energy x-ray region. Its equivalence to the optical E&M solution of the Fresnel equations at each interface is demonstrated by detailed comparisons for the reflectivity of a multilayer throughout the angular range of incidence of 0° to 90°. A special spectrograph and an experimental method are described for the measurement of the absolute reflectivity characteristics of the multilayer. The experimental measurements at three photon energies in the 100 to 2000 eV region are fit by the analytical modified Darwin-Prins equation (MDP) for 1(0), generating a detailed characterization of two state-of-the-art multilayers: sputtered tungsten-carbon with 2d 70 A and a molecular lead stearate with 2d 100 A. The fitting parameters that are determined by this procedure are applied to help establish the structural characteristics of these multilayers.

3. Electric Field Change Measurements of a Terrestrial Gamma Ray Flash

Marshall, Thomas; Karunarathne, Sumedhe; Stolzenburg, Maribeth

2016-04-01

Cummer et al. [GRL, 2014] reported on two terrestrial gamma ray flashes (TGFs) detected by the Gamma ray Burst Monitor (GBM) on the Fermi satellite. At a range of 632 km we detected an electric field change pulse associated with the first of these TGFs. The sensor bandwidth was 0.16 Hz - 2.6 MHz and was sampled at 5 MS/s. The measured zero-to-peak amplitude was 3.1 V/m. Assuming a 1/R range dependence, the amplitude range normalized to 100 km would be about 20 V/m. However, a little more than half of the path from the TGF to the sensor was over land rather than ocean, which should cause the attenuation to be greater than 1/R. Based on recent measurements of Kolmasova et al. (2015 AGU Fall Meeting), we estimate that the real peak amplitude was 40 - 50 V/m. The detected pulse was bipolar with a leading positive peak and had an overall duration of about 50 μs; these characteristics are typical of initial breakdown pulses (IBPs) that occur at the beginning of intracloud (IC) flashes. However, the pulse amplitude is an order of magnitude larger than typical IBPs. These data support the notion that IBPs of IC flashes cause TGFs [e.g., Shao et al., JGR 2010; Lu et al., GRL 2010; Cummer et al., GRL 2014].

4. Measurement of coronal X-ray emission lines from Capella

NASA Technical Reports Server (NTRS)

Vedder, P. W.; Canizares, C. R.

1983-01-01

The Einstein Observatory's Focal Plane Crystal Spectrometer has detected X-ray emission lines due to O VIII, Fe XVII, and Fe XX, from the binary star system Capella. Line luminosities are well fitted by an emitting plasma at a single temperature of 6.29 + or - 0.01 - 0.03 million K, and a volume emission measure of about 8.6 x 10 to the 52nd/cu cm, corresponding to the low temperature component previously observed. A high temperature component is undetectable, since the observed lines are not produced in plasma at temperatures above about 20 million K. Nearly isothermal plasma would be expected if many of the magnetically confined coronal loops have similar sizes and pressures, and a second population of longer loops would be required to account for the hotter component. An alternative interpretation of the observed X-ray line emission and upper limit is that the plasma contains a continuous distribution of emission measure versus temperature that rises sharply to 3 million K and then falls by nearly a decade to 16 million. An extrapolation of the loop sizes suggested by this alternative to hotter, longer loops may also account for the higher temperature emission.

5. The Locations of Gamma-Ray Bursts Measured by Comptel

NASA Technical Reports Server (NTRS)

Kippen, R. Marc; Ryan, James M.; Connors, Alanna; Hartmann, Dieter H.; Winkler, Christoph; Kuiper, Lucien; Varendorff, Martin; McConnell, Mark L.; Hurley, Kevin; Hermsen, Wim; Schoenfelder, Volker

1998-01-01

The COMPTEL instrument on the Compton Gamma Ray Observatory is used to measure the locations of gamma-ray bursts through direct imaging of MeV photons. In a comprehensive search, we have detected and localized 29 bursts observed between 1991 April 19 and 1995 May 31. The average location accuracy of these events is 1.25 deg (1 sigma), including a systematic error of approx. 0.5 deg, which is verified through comparison with Interplanetary Network (IPN) timing annuli. The combination of COMPTEL and IPN measurements results in locations for 26 of the bursts with an average "error box" area of only approx. 0.3 deg (1 sigma). We find that the angular distribution of COMPTEL burst locations is consistent with large-scale isotropy and that there is no statistically significant evidence of small-angle autocorrelations. We conclude that there is no compelling evidence for burst repetition since no more than two of the events (or approx. 7% of the 29 bursts) could possibly have come from the same source. We also find that there is no significant correlation between the burst locations and either Abell clusters of galaxies or radio-quiet quasars. Agreement between individual COMPTEL locations and IPN annuli places a lower limit of approx. 100 AU (95% confidence) on the distance to the stronger bursts.

6. Measurements of X-ray selected AGN and novel superconducting X-ray detectors

Eckart, Megan Elizabeth

2007-07-01

The second part of this thesis focuses on microwave kinetic inductance detectors (MKIDs), a superconducting detector technology that has breakthrough potential for providing megapixel imagers with several eV energy resolution for use in future X-ray missions. These detectors utilize simple, thin-film lithographed microwave resonators as photon detectors in a multiplexed readout approach. X-ray absorption in a superconductor creates quasiparticle excitations, with number proportional to the X-ray energy. The surface impedance of a superconductor changes with the quasiparticle density, and if operated at T<measured using the thin-film resonant circuit and microwave readout techniques. This provides a sensitive detector with excellent energy resolution. MKIDs offer the advantage over many other cryogenic detector technologies that they can be easily multiplexed by coupling many resonators to a single microwave transmission line. In addition, the readout electronics can be operated at room temperature, a significant advantage for space applications. The practical application of MKIDs for photon detection requires a method of efficiently coupling the photon energy to the MKID. To this end we have been studying MKIDs in a strip detector architecture. The second part of this thesis presents our results using strip detectors with tantalum absorbers coupled to aluminum MKIDs.

7. Molecular origins of conduction channels observed in shot-noise measurements.

PubMed

Solomon, Gemma C; Gagliardi, Alessio; Pecchia, Alessandro; Frauenheim, Thomas; Di Carlo, Aldo; Reimers, Jeffrey R; Hush, Noel S

2006-11-01

Measurements of shot noise from single molecules have indicated the presence of various conduction channels. We present three descriptions of these channels in molecular terms showing that the number of conduction channels is limited by bottlenecks in the molecule and that the channels can be linked to transmission through different junction states. We introduce molecular-conductance orbitals, which allow the transmission to be separated into contributions from individual orbitals and contributions from interference between pairs of orbitals. PMID:17090069

8. MEASURING VERTICAL PROFILES OF HYDRAULIC CONDUCTIVITY WITH IN SITU DIRECT-PUSH METHODS

EPA Science Inventory

U.S. EPA (Environmental Protection Agency) staff developed a field procedure to measure hydraulic conductivity using a direct-push system to obtain vertical profiles of hydraulic conductivity. Vertical profiles were obtained using an in situ field device-composed of a
Geopr...

9. IN SITU APPARENT CONDUCTIVITY MEASUREMENTS AND MICROBIAL POPULATION DISTRIBUTION AT A HYDROCARBON CONTAMINATED SITE

EPA Science Inventory

We investigated the bulk electrical conductivity and microbial population distribution in sediments at a site contaminated with light non-aqueous phase liquid (LNAPL). The bulk conductivity was measured using in situ vertical resistivity probes, while the most probable number met...

10. Longitudinal detection of ferromagnetic resonance using x-ray transmission measurements

SciTech Connect

Boero, G.; Rusponi, S.; Kavich, J.; Rizzini, A. Lodi; Piamonteze, C.; Nolting, F.; Tieg, C.; Thiele, J.-U.; Gambardella, P.

2009-12-15

We describe a setup for the x-ray detection of ferromagnetic resonance in the longitudinal geometry using element-specific transmission measurements. Thin magnetic film samples are placed in a static magnetic field collinear with the propagation direction of a polarized soft x-ray beam and driven to ferromagnetic resonance by a continuous wave microwave magnetic field perpendicular to it. The transmitted photon flux is measured both as a function of the x-ray photon energy and as a function of the applied static magnetic field. We report experiments performed on a 15 nm film of doped Permalloy (Ni{sub 73}Fe{sub 18}Gd{sub 7}Co{sub 2}) at the L{sub 3}/L{sub 2}-edges of Fe, Co, and Ni. The achieved ferromagnetic resonance sensitivity is about 0.1 monolayers/{radical}(Hz). The obtained results are interpreted in the framework of a conductivity tensor based formalism. The factors limiting the sensitivity as well as different approaches for the x-ray detection of ferromagnetic resonance are discussed.

11. The Thermal Conductivity Measurements of Solid Samples by Heat Flux Differantial Scanning Calorimetry

Kök, M.; Aydoǧdu, Y.

2007-04-01

The thermal conductivity of polyvinylchloride (PVC), polysytrene (PS) and polypropylene (PP) were measured by heat flux DSC. Our results are in good agreement with the results observed by different methods.

12. Measuring the sedimentation rate in a magnetorheological fluid column via thermal conductivity monitoring

Cheng, Haibin; Zhang, Xiaopeng; Liu, Guizhen; Ma, Wentao; Wereley, Norman M.

2016-05-01

Measuring sedimentation rate of magnetorheological fluids (MRFs) is of great importance when designing and synthesizing MRFs for engineering applications. A method of characterizing sedimentation rate in an MRF column is proposed utilizing thermal conductivity correlated with particle concentration. A series of MRF samples composed of carbonyl iron particles suspended in silicone oil were prepared, and their concentrations (measured as volume fraction, ∅) and thermal conductivities, k, were tested. A calibration curve was developed to relate particle concentration, ∅, to thermal conductivity, k, using this set of MRF samples with known concentration. The particle concentration, ∅, in the MRF column was then monitored by measuring thermal conductivities (k) at a fixed location and using this calibration relationship. Finally, sedimentation rate in the MRF column was determined by examining how particle concentration varied with time. The sedimentation rate measured in the MRF column was validated using visual observation of mudline (boundary between the topmost clarified fluid zone and MRF below).

13. Compressional stress effect on thermal conductivity of powdered materials: Measurements and their implication to lunar regolith

Sakatani, Naoya; Ogawa, Kazunori; Iijima, Yu-ichi; Arakawa, Masahiko; Tanaka, Satoshi

2016-03-01

Thermal conductivity of powdered materials under vacuum conditions is a valuable physical parameter in the context of planetary sciences. We report results of thermal conductivity measurements of 90-106 μm and 710-1000 μm glass beads, and lunar regolith simulant using two different experimental setups for varying the compressional stress and the temperature, respectively. We found the thermal conductivity increase with the compressional stress, for example, from 0.003 to 0.008 W m-1 K-1 for the glass beads of 90-106 μm in diameter at the compressional stress less than 20 kPa. This increase of the thermal conductivity is attributed the areal enlargement of the contacts between particles due to their elastic deformation. The thermal conductivity increased also with temperature, which primarily represented enhancement of the radiative heat conduction between particles. Reduction of the estimated radiative conductivity from the effective thermal conductivity obtained in the first experiment yields the relation between the solid conductivity (conductive contribution through inter-particle contacts) and the compressional stress. We found that the solid conductivity is proportional to approximately 1/3 power of the compressional stress for the glass beads samples, while the regolith simulant showed a weaker exponent than that of the glass beads. We developed a semi-empirical expression of the thermal conductivity of the lunar regolith using our data on the lunar regolith simulant. This model enabled us to estimate a vertical distribution of the lunar subsurface thermal conductivity. Our model provides an examination for the density and compressional stress relationships to thermal conductivity observed in the in-situ measurements in Apollo 15 and 17 Heat Flow Experiments.

14. X-ray and ultraviolet radiation from accreting white dwarfs. IV - Two-temperature treatment with electron thermal conduction

NASA Technical Reports Server (NTRS)

Imamura, J. N.; Durisen, R. H.; Lamb, D. Q.; Weast, G. J.

1987-01-01

Results are reported from two-temperature calculations of the structures and X-ray spectra of radiation shocks generated by accretion onto nonmagnetic white dwarfs. The approach was necessitated by the domination of bremsstrahlung in the emission region by Compton cooling. Features of the shock model, which includes steady, spherical infall of fully ionized plasma and dominance of the stand-off shock by collisional processes, are summarized. A maximum hard X-ray temperature of about 50 keV and a maximum hard X-ray luminosity of 2 x 10 to the 36th ergs/sec were obtained. The results prove that the bulk of accretion energy cannot be transported to the star by electron thermal conduction, provided that bremsstrahlung cooling is dominant over cyclotron cooling.

15. Electronic energy gap of molecular hydrogen from electrical conductivity measurements at high shock pressures

NASA Technical Reports Server (NTRS)

Nellis, W. J.; Mitchell, A. C.; Mccandless, P. C.; Erskine, D. J.; Weir, S. T.

1992-01-01

Electrical conductivities were measured for liquid D2 and H2 shock compressed to pressures of 10-20 GPa (100-200 kbar), molar volumes near 8 cu cm/mol, and calculated temperatures of 2900-4600 K. The semiconducting energy gap derived from the conductivities is 12 eV, in good agreement with recent quasi-particle calculations and with oscillator frequencies measured in diamond-anvil cells.

16. Electrical conductivity and equation of state measurements on planetary fluids at high pressures and temperatures

SciTech Connect

Hamilton, D.C.; Nellis, W.J.; Holmes, N.C.; Radousky, H.B.; Ree, F.H.; Nicol, M.

1987-07-01

Hugoniot equation-of-state, shock temperature, and electrical conductivity measurements are reported for fluids believed to be the primary constituents of the planets Uranus and Neptune. The equation-of-state results are compared with calculations performed using a statistical mechanical, chemical equilibrium computer code and electrical conductivities are discussed in terms of the recently measured magnetic field of Uranus. 4 refs., 2 figs., 1 tab.

17. X-ray based displacement and strain measurements for hostile environments

NASA Technical Reports Server (NTRS)

Canistraro, Howard A.; Jordan, Eric H.; Pease, Douglas M.

1993-01-01

A completely new method of non-contacting, hostile environment displacement and strain measurement based on the focus and scanning of x-rays, has been developed and demonstrated. The new technique has the ability to overcome many of the limitations associated with available methods. The system is based on the focus and scanning of low energy, hard x-rays such as those emanating from table top copper or molybdenum sources. The x-rays are focused into a narrow and intense line image which can be swept onto targets that fluoresce secondary x-ray radiation. By monitoring the secondary radiation intensity and comparing it with the focused x-ray image's position as it is swept over the target edge, the position of the target edge relative to the focused image can be determined. The present system has a resolution of 0.5 micron, which has been shown to be limited by bearing backlash (or 'yaw' error) in the linear translation table. Its use has been demonstrated in the presence of an open flame with a resultant target temperature in excess of 2000 degrees Fahrenheit (1000 degrees Celsius). Strain measurements have been conducted in a laboratory environment at both room temperature and at a specimen temperature of 1300 degrees Fahrenheit, with an accuracy of within 20 microstrain (primarily a function of the 0.5 micron resolution limit). The main advantage of the technique lies in the penetrating, non-refractive nature of x-rays, which are virtually immune to the presence of refracting gas layers, smoke, flame or intense thermal radiation.

18. Thermal-Conductivity Measurement of Thermoelectric Materials Using 3{{\\upomega }} Method

Hahtela, O.; Ruoho, M.; Mykkänen, E.; Ojasalo, K.; Nissilä, J.; Manninen, A.; Heinonen, M.

2015-12-01

In this work, a measurement system for high-temperature thermal-conductivity measurements has been designed, constructed, and characterized. The system is based on the 3{\\upomega } method which is an ac technique suitable for both bulk and thin-film samples. The thermal-conductivity measurements were performed in a horizontal three-zone tube furnace whose sample space can be evacuated to vacuum or alternatively a protective argon gas environment can be applied to prevent undesired oxidation and contamination of the sample material. The system was tested with several dielectric, semiconductor, and metal bulk samples from room temperature up to 725 K. The test materials were chosen so that the thermal-conductivity values covered a wide range from 0.37 W\\cdot m^{-1}\\cdot K^{-1} to 150 {} \\cdot m^{-1}\\cdot K^{-1}. An uncertainty analysis for the thermal-conductivity measurements was carried out. The measurement accuracy is mainly limited by the determination of the third harmonic of the voltage over the resistive metal heater strip that is used for heating the sample. A typical relative measurement uncertainty in the thermal-conductivity measurements was between 5 % and 8 % (k=2). An extension of the 3{\\upomega } method was also implemented in which the metal heater strip is first deposited on a transferable Kapton foil. Utilizing such a prefabricated sensor allows for faster measurements of the samples as there is no need to deposit a heater strip on each new sample.

19. Hot wire needle probe for in-reactor thermal conductivity measurement

SciTech Connect

JE Daw; JL Rempe; DL Knudson

2012-08-01

Thermal conductivity is a key property that must be known for proper design, test, and application of new fuels and structural materials in nuclear reactors. Thermal conductivity is highly dependent on the physical structure, chemical composition, and the state of the material. Typically, thermal conductivity changes that occur during irradiation are measured out-of-pile by Post Irradiated Examination (PIE) using a “cook and look” approach in hot-cells. Repeatedly removing samples from a test reactor to make out-of-pile measurements is expensive, has the potential to disturb phenomena of interest, and only provides understanding of the sample's end state at the time each measurement is made. There are also limited thermophysical property data for advanced fuels. Such data are needed for simulation design codes, the development of next generation reactors, and advanced fuels for existing nuclear plants. Being able to quickly characterize fuel thermal conductivity during irradiation can improve the fidelity of data, reduce costs of post-irradiation examinations, increase understanding of how fuels behave under irradiation, and confirm or improve existing thermal conductivity measurement techniques. This paper discusses recent efforts to develop and evaluate an in-pile thermal conductivity sensor based on a hot wire needle probe. Testing has been performed on samples with thermal conductivities ranging from 0.2 W/m-K to 22 W-m-K in temperatures ranging from 20 °C to 600 °C. Thermal conductivity values measured using the needle probe match data found in the literature to within 5% for samples tested at room temperature, 5.67% for low thermal conductivity samples tested at high temperatures, and 10% for high thermal conductivity samples tested at high temperatures. Experimental results also show that this sensor is capable of operating in various test conditions and of surviving long duration irradiations.

20. Building up graphene-based conductive polymer composite thin films using reduced graphene oxide prepared by γ-ray irradiation.

PubMed

Xie, Siyuan; Zhang, Bowu; Wang, Chunlei; Wang, Ziqiang; Li, Linfan; Li, Jingye

2013-01-01

In this paper, reduced graphene oxide (RGO) was prepared by means of γ -ray irradiation of graphene oxide (GO) in a water/ethanol mix solution, and we investigated the influence of reaction parameters, including ethanol concentration, absorbed dose, and dose rate during the irradiation. Due to the good dispersibility of the RGO in the mix solution, we built up flexible and conductive composite films based on the RGO and polymeric matrix through facile vacuum filtration and polymer coating. The electrical and optical properties of the obtained composite films were tested, showing good electrical conductivity with visible transmittance but strong ultraviolet absorbance. PMID:24170985

1. ON THE STATISTICAL ANALYSIS OF X-RAY POLARIZATION MEASUREMENTS

SciTech Connect

Strohmayer, T. E.; Kallman, T. R.

2013-08-20

In many polarimetry applications, including observations in the X-ray band, the measurement of a polarization signal can be reduced to the detection and quantification of a deviation from uniformity of a distribution of measured angles of the form A + Bcos {sup 2}({phi} - {phi}{sub 0}) (0 < {phi} < {pi}). We explore the statistics of such polarization measurements using Monte Carlo simulations and {chi}{sup 2} fitting methods. We compare our results to those derived using the traditional probability density used to characterize polarization measurements and quantify how they deviate as the intrinsic modulation amplitude grows. We derive relations for the number of counts required to reach a given detection level (parameterized by {beta} the ''number of {sigma}'s'' of the measurement) appropriate for measuring the modulation amplitude a by itself (single interesting parameter case) or jointly with the position angle {phi} (two interesting parameters case). We show that for the former case, when the intrinsic amplitude is equal to the well-known minimum detectable polarization, (MDP) it is, on average, detected at the 3{sigma} level. For the latter case, when one requires a joint measurement at the same confidence level, then more counts are needed than what was required to achieve the MDP level. This additional factor is amplitude-dependent, but is Almost-Equal-To 2.2 for intrinsic amplitudes less than about 20%. It decreases slowly with amplitude and is Almost-Equal-To 1.8 when the amplitude is 50%. We find that the position angle uncertainty at 1{sigma} confidence is well described by the relation {sigma}{sub {phi}} = 28. Degree-Sign 5/{beta}.

2. Features of the electrical conductivity of TlInSe{sub 2} under photoexcitation and X-ray excitation

SciTech Connect

Madatov, R. S. Najafov, A. I.; Mustafayev, Yu. M.; Gazanfarov, M. R.; Movsumova, I. M.

2015-09-15

The current–voltage characteristics of TlInSe{sub 2} crystals under photoexcitation and X-ray excitation are studied. The parameters of the trap, which are equal to N{sub t} = 5 × 10{sup 16} cm{sup –3}, n{sub t} = 4.5 × 10{sup 12} cm{sup –3}, and ΔE{sub t} = 0.42 eV, are calculated. The calculated values of N{sub t} and n{sub t} before and after X-ray excitation are equal to 3 × 10{sup 16} cm{sup –3} and 3.2 × 10{sup 12} cm{sup –3}, respectively. The dependences of the X-ray conductances on the radiation intensity are studied for TlInSe{sub 2} crystals at various accelerating voltages V{sub a} and it is determined that the X-ray conductance K{sub σ} decreases exponentially as the accelerating voltage V{sub a} and radiation dose increase.

3. Chemical state of Ag in Conducting Bridge Random Access Memory cells: a depth resolved X-ray Absorption Spectroscopy investigation.

d'Acapito, F.; Souchier, E.; Noe, P.; Blaise, P.; Bernard, M.; Jousseaume, V.

2016-05-01

Conducting Bridge Random Access Memories (CBRAM) are a promising substitute for FLASH technology but problems with limited retention of the low resistance ON state still hamper their massive deployment. Depth resolved X-ray Absorption Spectroscopy has been used to describe the chemical state of the atoms of the active electrode (in this case Ag) and to reveal the role of Sb as stabilizer of the metallic state.

4. X-Ray Measured Dynamics of Tycho's Supernova Remnant

NASA Technical Reports Server (NTRS)

Katsuda, Satoru; Petre, Robert; Hughes, John; Hwang, Una; Yamaguchi, Hiroya; Hayato, Asami; Mori, Koji; Tsunemi, Hiroshi

2010-01-01

We present X-ray proper-motion measurements of the forward shock and reverse-shocked ejecta in Tycho's supernova remnant, based on three sets of archival Chandra data taken in 2000, 2003, and 2007. We find that the proper motion of the edge of the remnant (i.e., the forward shock and protruding ejecta knots) varies from 0.''20 yr-1 (expansion index m = 0.33, where R = tm ) to 0.''40 yr-1 (m = 0.65) with azimuthal angle in 2000-2007 measurements, and 0.''14 yr-1 (m = 0.26) to 0.''40 yr-1 (m = 0.65) in 2003-2007 measurements. The azimuthal variation of the proper motion and the average expansion index of [approx]0.5 are consistent with those derived from radio observations. We also find proper motion and expansion index of the reverse-shocked ejecta to be 0.''21-0.''31 yr-1 and 0.43-0.64, respectively. From a comparison of the measured m-value with Type Ia supernova evolutionary models, we find a pre-shock ambient density around the remnant of [less, similar]0.2 cm-3.

5. Design and Use of a Novel Apparatus for Measuring Capsule Fill Hole Conductance

SciTech Connect

Seugling, R M; Nederbragt, W W; Klingmann, J L; Edson, S; Reynolds, J; Cook, R

2006-11-27

Description and results of a novel apparatus for determining the flow conductance through a laser drilled hole in a spherical shell for inertial confinement fusion experiments are described. The instrument monitors the pressure of an enclosed volume containing the laser pressure drilled capsule as air bleeds through the hole into the shell. From these measurements one obtains the conductance of the fill hole. This system has proven to be a valuable tool for verifying the conduct conductance into the capsule in a timely and nondestructive manner.

6. A convenient method of measuring the thermal conductivity of biological tissue.

PubMed

Liang, X G; Ge, X S; Zhang, Y P; Wang, G J

1991-12-01

The basic principle of the thermal conductivity probe is described. Thin probes were developed based on this principle, with a reproducibility of 5.3% and relative error less than 6.0%. Each measurement can be completed in 90 s and the temperature increase can be controlled within 2 degrees C. Using the probes, the thermal conductivities of pig fat, meat, liver, kidney and live and dead snake head were measured and it was found that water content plays an important role in influencing the magnitude of the thermal conductivity of biological tissues. The probe can be used over a temperature range from -40 to 150 degrees C. PMID:1771182

7. In-core measurements of U-5 wt % fissium alloy thermal conductivity

SciTech Connect

Betten, P.R.

1985-01-01

Instrumented subassemblies have inserted into the Experimental Breeder Reactor II (EBR-II) in order to monitor thermal-hydraulic phenomena. For one such subassembly, a time history of the in-core themocouples was evaluated and used to determine the fuel thermal conductivity. Although several researchers have evaluated fuel conductivity for unirradiated conditions, little data is available for long term irradiation. Further, most of the data has been evaluated under laboratory conditions which, while providing exact measurements, may be missing important facets of in-core behavior. The purpose of this paper is to present the in-situ measurements of thermal conductivity over the subassembly lifetime. 7 refs.

8. Uncertainty Of The Measurement Of DC Conductivity Of Eramics At Elevated Temperatures

Štubňa, Igor; Trnovcová, Viera; Vozár, Libor; Csáki, Štefan

2015-01-01

The electrical DC conductivity is measured at room and elevated temperatures on green ceramic samples prepared from kaolin. The arrangement of the sample, with two platinum wire electrodes inserted in the kaolin prism that was used is suitable for measurements of temperature dependences of the DC conductivity from 20 °C to 1100 °C in the air. The uncertainty analysis taking into account thermal expansion of the sample, homogeneity of the temperature field, measurement regime, corrosion of the electrodes, and overlapping of the electrodes is done for 1000 °C. Uncertainties connected with current and voltage measurements and uncertainties connected with the instruments that were used are also considered. The sum of all the partial uncertainties gives an expanded uncertainty of the conductivity measurement. The uncertainty varies with temperature and reaches the value of ˜ 6.5% at 1000 °C.

9. Conductivity Variation Observed by Polarization and Depolarization Current Measurements of High-Voltage Equipment Insulation System

Jamail, Nor Akmal Mohd; Piah, Mohamed Afendi Mohamed; Muhamad, Nor Asiah

2012-09-01

Nondestructive and time domain dielectric measurement techniques such as polarization and depolarization current (PDC) measurements have recently been widely used as a potential tool for determining high-voltage insulation conditions by analyzing the insulation conductivity. The variation in the conductivity of an insulator was found to depend on several parameters: the difference between the polarization and depolarization currents, geometric capacitance, and the relative permittivity of the insulation material. In this paper the conductivities of different types of oil-paper insulation material are presented. The insulation conductivities of several types of electrical apparatus were simulated using MATLAB. Conductivity insulation was found to be high at high polarizations and at the lowest depolarization current. It was also found to increase with increasing relative permittivity as well as with decreasing geometric capacitance of the insulating material.

10. Design and Validation of a High-Temperature Comparative Thermal-Conductivity Measurement System

SciTech Connect

Jeff Phillips; Colby Jensen; C Xing; H. Ban

2012-02-01

A measurement system has been designed and built for the specific application of measuring the effective thermal conductivity of a composite, nuclear-fuel compact (small cylinder) over a temperature range of 100 C to 800 C. Because of the composite nature of the sample as well as the need to measure samples pre- and postirradiation, measurement must be performed on the whole compact non-destructively. No existing measurement system is capable of obtaining its thermal conductivity in a non-destructive manner. The designed apparatus is an adaptation of the guardedcomparative-longitudinal heat flow technique. The system uniquely demonstrates the use of a radiative heat sink to provide cooling which greatly simplifies the design and setup of such high-temperature systems. The design was aimed to measure thermalconductivity values covering the expected range of effective thermal conductivity of the composite nuclear fuel from 10W {center_dot} m{sup -1} {center_dot} K{sup -1} to 70W {center_dot} m{sup -1} {center_dot} K{sup -1}. Several materials having thermal conductivities covering this expected range have been measured for system validation, and results are presented. A comparison of the results has been made to data from existing literature.Additionally, an uncertainty analysis is presented finding an overall uncertainty in sample thermal conductivity to be 6%, matching well with the results of the validation samples.

11. Measurements of X-ray scattering from interstellar grains

NASA Technical Reports Server (NTRS)

Mauche, C. W.; Gorenstein, P.

1986-01-01

The results of an Einstein Observatory imaging proportional counter investigation of the halos produced by the scattering of X-rays from interstellar grains of four compact Galactic (low-latitude) and two extragalactic (high-latitude) X-ray sources are reported. It is found that the intensity of these halos correlates well with the amount of visual extinction and the distance through the Galaxy's dust layer: quantities which measure the column density of grains to a given source. From this result, and from the size and shape of the halos from the Galactic sources, a number of grain parameters are derived in the context of two alternate grain size distributions: the Mathis-Rumpl-Nordsieck (MRN) and the Oort-van de Hulst distributions, either of which is capable of producing the observed halos. Though no single grain size is capable of producing the shapes observed for these halos, a mean size of about 0.1 micron and a number density of about 10 to the -12th grains/cu cm produce the correct halo intensities. From the additional parameters determined from the size and shape of the halos, results concerning the amount of material in grains which are in general agreement with the observed depletion of the elements from the gas phase of the interstellar medium, as well as with the detailed predictions of the MRN size distribution, are found.

12. Measuring Cosmological Parameters with Gamma-Ray Bursts

Amati, Lorenzo; Valle, Massimo Della

2015-01-01

Gamma-Ray Bursts (GRB) emit in a few dozen of seconds up to ~1054 erg, in terms of isotropic equivalent radiated energy Eiso, therefore they can be observed up to z ~ 10 and appear very promising tools to describe the expansion rate history of the Universe. In this paper we review the use of the Ep,i-Eiso correlation of Gamma-Ray Bursts to measure ΩM. We show that the present data set of GRBs, coupled with the assumption that we live in a flat universe, can provide indipendent evidence, from other probes, that ΩM~0.3. We show that current (e.g., Swift, Fermi/GBM, Konus-WIND) and next GRB experiments (e.g., CALET/GBM, SVOM, Lomonosov/UFFO, LOFT/WFM) will allow us, within a few years, to constrain ΩM and the evolution of dark energy with time, with an accuracy comparable to that currently exhibited by SNe-Ia.

13. Measuring Performance of Energy-Dispersive X-ray Systems.

PubMed

Statham

1998-11-01

: As Si(Li) detector technology has matured, many of the fundamental problems have been addressed in the competition among manufacturers and there is now an expectation, implied by many textbooks, that all energy-dispersive X-ray (EDX) detectors are made and will perform in the same way. Although there has been some convergence in Si(Li) systems and these are still the most common, manufacturing recipes still differ and there are many alternative EDX devices, such as microcalorimeters and room temperature detectors, that have both advantages and disadvantages over Si(Li). Rather than emphasizing differences in technologies, performance measures should reveal benefits relevant to the intended application. The instrument is inevitably going to be a "black box" of integrated components; this article reviews some of the methods that have been applied and introduces some new techniques that can be used to assess performance without resorting to complex software or sophisticated mathematical algorithms. Sensitivity, resolution, artefacts, and stability are discussed with particular application to compositional analysis using electron beam excitation of X-rays in the 100-eV to 10-keV energy region. PMID:10087283

14. Ultra-sensitive thermal conductance measurement of one-dimensional nanostructures enhanced by differential bridge.

PubMed

Wingert, Matthew C; Chen, Zack C Y; Kwon, Shooshin; Xiang, Jie; Chen, Renkun

2012-02-01

Thermal conductivity of one-dimensional nanostructures, such as nanowires, nanotubes, and polymer chains, is of significant interest for understanding nanoscale thermal transport phenomena as well as for practical applications in nanoelectronics, energy conversion, and thermal management. Various techniques have been developed during the past decade for measuring this fundamental quantity at the individual nanostructure level. However, the sensitivity of these techniques is generally limited to 1 × 10(-9) W∕K, which is inadequate for small diameter nanostructures that potentially possess thermal conductance ranging between 10(-11) and 10(-10) W∕K. In this paper, we demonstrate an experimental technique which is capable of measuring thermal conductance of ∼10(-11) W∕K. The improved sensitivity is achieved by using an on-chip Wheatstone bridge circuit that overcomes several instrumentation issues. It provides a more effective method of characterizing the thermal properties of smaller and less conductive one-dimensional nanostructures. The best sensitivity experimentally achieved experienced a noise equivalent temperature below 0.5 mK and a minimum conductance measurement of 1 × 10(-11) W∕K. Measuring the temperature fluctuation of both the four-point and bridge measurements over a 4 h time period shows a reduction in measured temperature fluctuation from 100 mK to 0.6 mK. Measurement of a 15 nm Ge nanowire and background conductance signal with no wire present demonstrates the increased sensitivity of the bridge method over the traditional four-point I-V measurement. This ultra-sensitive measurement platform allows for thermal measurements of materials at new size scales and will improve our understanding of thermal transport in nanoscale structures. PMID:22380117

15. Thermal Conductivity Measurement of an Electron-Beam Physical-Vapor-Deposition Coating

PubMed Central

Slifka, A. J.; Filla, B. J.

2003-01-01

An industrial ceramic thermal-barrier coating designated PWA 266, processed by electron-beam physical-vapor deposition, was measured using a steady-state thermal conductivity technique. The thermal conductivity of the mass fraction 7 % yttria-stabilized zirconia coating was measured from 100 °C to 900 °C. Measurements on three thicknesses of coatings, 170 μm, 350 μm, and 510 μm resulted in thermal conductivity in the range from 1.5 W/(m·K) to 1.7 W/(m·K) with a combined relative standard uncertainty of 20 %. The thermal conductivity is not significantly dependent on temperature.

16. Measurement of the across-plane conductivity of YSZ thin films on silicon

PubMed Central

Navickas, E.; Gerstl, M.; Friedbacher, G.; Kubel, F.; Fleig, J.

2012-01-01

Across-plane conductivity measurements on ion conducting thin films of a few ten nanometers thickness are challenging due to frequently occurring short-circuits through pinholes in the layer. In this contribution, a method is proposed which allowed across-plane conductivity measurements on yttria stabilized zirconia (YSZ) layers with thicknesses as low as 20 nm. YSZ layers were prepared onto silicon substrates with a thin native silica interlayer and the across-plane conductivity was measured on circular microelectrodes by impedance spectroscopy. The silica interlayer exhibits strongly blocking behavior, which helps to avoid short-circuits through pinholes. Different relaxation frequencies of YSZ and silica make separation of these layers possible. An equivalent circuit is suggested, which allows extraction of YSZ properties, and its validity is proven by varying microelectrodes size and layer thickness. All parameters yield the expected behavior.

17. Thermal conductivity and diffusivity of biomaterials measured with self-heated thermistors

Valvano, J. W.; Cochran, J. R.; Diller, K. R.

1985-05-01

This paper presents an experimental method to measure the thermal conductivity and thermal diffusivity of biomaterials. Self-heated thermistor probes, inserted into the tissue of interest, are used to deliver heat as well as to monitor the rate of heat removal. An empirical calibration procedure allows accurate thermal-property measurements over a wide range of tissue temperatures. Operation of the instrument in three media with known thermal properties shows the uncertainty of measurements to be about 2%. The reproducibility is 0.5% for the thermal-conductivity measurements and 2% for the thermal-diffusivity measurements. Thermal properties were measured in dog, pig, rabbit, and human tissues. The tissues included kidney, spleen, liver, brain, heart, lung, pancreas, colon cancer, and breast cancer. Thermal properties were measured for 65 separate tissue samples at 3, 10, 17, 23, 30, 37, and 45°C. The results show that the temperature coefficient of biomaterials approximates that of water.

18. A measurement of the antiproton flux in the cosmic rays

NASA Technical Reports Server (NTRS)

Buffington, A.; Schindler, S. M.

1981-01-01

A balloon-borne instrument has been used to detect cosmic-ray antiprotons. These are identified topologically by the appearance of annihilation prongs in a thick lead-plate spark chamber. The initial recording of the data is enriched in potential antimatter events by a selective trigger. After a small subtraction for background, 14 identified antiprotons yield a flux of 1.7 plus or minus 0.00005 antiproton/(sq m ster sec MeV) between 130 and 320 MeV at the top of the atmosphere. When combined with higher energy antiproton flux measurements, this result indicates that the antiprotons have a spectrum whose shape is the same as that of the protons, but with a magnitude reduced by a factor of 1/3000.

19. X-ray PIV measurement of blood flow in deep vessels of a rat: An in vivo feasibility study

PubMed Central

Park, Hanwook; Yeom, Eunseop; Lee, Sang Joon

2016-01-01

X-ray PIV measurement is a noninvasive approach to measure opaque blood flows. However, it is not easy to measure real pulsatile blood flows in the blood vessels located at deep position of the body, because the surrounding tissues significantly attenuate the contrast of X-ray images. This study investigated the effect of surrounding tissues on X-ray beam attenuation by measuring the velocity fields of blood flows in deep vessels of a live rat. The decrease in image contrast was minimized by employing biocompatible CO2 microbubbles as tracer particles. The maximum measurable velocity of blood flows in the abdominal aorta of a rat model was found through comparative examination between the PIV measurement accuracy and the level of image contrast according to the input flow rate. Furthermore, the feasibility of using X-ray PIV to accurately measure in vivo blood flows was demonstrated by determining the velocity field of blood flows in the inferior vena cava of a rat. This study may serve as a reference in conducting in vivo X-ray PIV measurements of pulsatile blood flows in animal disease models and investigating hemodynamic characteristics and circulatory vascular diseases. PMID:26777719

20. Measurements of the vertical atmospheric electric field and of the electrical conductivity with stratospheric balloons

NASA Technical Reports Server (NTRS)

Iversen, I. B.; Madsen, M. M.; Dangelo, N.

1985-01-01

Measurements of the atmospheric (vertical) electric field with balloons in the stratosphere are reported. The atmospheric electrical conductivity is also measured and the current density inferred. The average vertical current shows the expected variation with universal time and is also seen to be influenced by external (magnetospheric) electric fields.

1. Development of a Handmade Conductivity Measurement Apparatus and Application to Vegetables and Fruits

ERIC Educational Resources Information Center

Set, Seng; Kita, Masakazu

2014-01-01

This paper describes the development of a simple handmade conductivity measurement apparatus based on a Kohlrausch bridge with inexpensive materials. We have examined the reliability of this apparatus with standard solutions and then measured juices of vegetables and fruits as well as a sports drink. Comparisons to total alkali content as…

2. Estimation of hydraulic conductivities of Yucca Mountain tuffs from sorptivity and water retention measurements

SciTech Connect

1995-06-01

The hydraulic conductivity functions of the matrix rocks at Yucca Mountain, Nevada, are among the most important data needed as input for the site-scale hydrological model of the unsaturated zone. The difficult and time-consuming nature of hydraulic conductivity measurements renders it infeasible to directly measure this property on large numbers of cores. Water retention and sorptivity measurements, however, can be made relatively rapidly. The sorptivity is, in principle, a unique functional of the conductivity and water retention functions. It therefore should be possible to invert sorptivity and water retention measurements in order to estimate the conductivity; the porosity is the only other parameter that is required for this inversion. In this report two methods of carrying out this inversion are presented, and are tested against a limited data set that has been collected by Flint et al. at the USGS on a set of Yucca Mountain tuffs. The absolute permeability is usually predicted by both methods to within an average error of about 0.5 - 1.0 orders of magnitude. The discrepancy appears to be due to the fact that the water retention curves have only been measured during drainage, whereas the imbibition water retention curve is the one that is relevant to sorptivity measurements. Although the inversion methods also yield predictions of the relative permeability function, there are yet no unsaturated hydraulic conductivity data against which to test these predictions.

3. Measurement uncertainty in Total Reflection X-ray Fluorescence

Floor, G. H.; Queralt, I.; Hidalgo, M.; Marguí, E.

2015-09-01

Total Reflection X-ray Fluorescence (TXRF) spectrometry is a multi-elemental technique using micro-volumes of sample. This work assessed the components contributing to the combined uncertainty budget associated with TXRF measurements using Cu and Fe concentrations in different spiked and natural water samples as an example. The results showed that an uncertainty estimation based solely on the count statistics of the analyte is not a realistic estimation of the overall uncertainty, since the depositional repeatability and the relative sensitivity between the analyte and the internal standard are important contributions to the uncertainty budget. The uncertainty on the instrumental repeatability and sensitivity factor could be estimated and as such, potentially relatively straightforward implemented in the TXRF instrument software. However, the depositional repeatability varied significantly from sample to sample and between elemental ratios and the controlling factors are not well understood. By a lack of theoretical prediction of the depositional repeatability, the uncertainty budget can be based on repeat measurements using different reflectors. A simple approach to estimate the uncertainty was presented. The measurement procedure implemented and the uncertainty estimation processes developed were validated from the agreement with results obtained by inductively coupled plasma - optical emission spectrometry (ICP-OES) and/or reference/calculated values.

4. A System for Conducting Sophisticated Mechanical Tests in Situ with High Energy Synchrotron X-Rays Final Technical Report

SciTech Connect

Jeremy Weiss

2012-08-02

5. Thermal-contact-conductance measurement for high-heat-load optics components at SPring-8

Takeuchi, T.; Tanaka, M.; Senba, Y.; Ohashi, H.; Goto, S.

2011-09-01

Thermal contact in water-cooling or cryogenic cooling-cooling condition is used for forming a high-heat-load component at the synchrotron radiation beamline. In SPring-8, for example, cryogenic cooling is used for silicon monochromator crystal with an indium insertion metal at the interface between a copper block and a silicon crystal. To reduce the strain on the silicon crystal with a low contact pressure and a high thermal conductivity, we require a silicon-indium-copper system and an alternative insertion material such as a graphite foil. To measure the thermal contact conductance in a quick measurement cycle under various thermal-contact conditions, we improve the thermal-contact-conductance measurement system in terms of the setup facilitation, precise temperature measurement, and thermal insulation around a sample.

6. Note: Development of a microfabricated sensor to measure thermal conductivity of picoliter scale liquid samples

Park, Byoung Kyoo; Yi, Namwoo; Park, Jaesung; Kim, Dongsik

2012-10-01

This paper presents a thermal analysis device, which can measure thermal conductivity of picoliter scale liquid sample. We employ the three omega method with a microfabricated AC thermal sensor with nanometer width heater. The liquid sample is confined by a micro-well structure fabricated on the sensor surface. The performance of the instrument was verified by measuring the thermal conductivity of 27-picoliter samples of de-ionized (DI) water, ethanol, methanol, and DI water-ethanol mixtures with accuracies better than 3%. Furthermore, another analytical scheme allows real-time thermal conductivity measurement with 5% accuracy. To the best of our knowledge, this technique requires the smallest volume of sample to measure thermal property ever.

7. Soft x-ray measurements using photoconductive type-IIa and single-crystal chemical vapor deposited diamond detectors

SciTech Connect

Moore, A. S.; Bentley, C. D.; Foster, J. M.; Goedhart, G.; Graham, P.; Taylor, M. J.; Hellewell, E.

2008-10-15

Photoconductive detectors (PCDs) are routinely used alongside vacuum x-ray diodes (XRDs) to provide an alternative x-ray flux measurement at laser facilities such as HELEN at AWE Aldermaston, UK, and Omega at the Laboratory for Laser Energetics. To evaluate diamond PCDs as an alternative to XRD arrays, calibration measurements made at the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory are used to accurately calculate the x-ray flux from a laser-heated target. This is compared to a flux measurement using the Dante XRD diagnostic. Estimates indicate that the photoinduced conductivity from measurements made at Omega are too large, and calculations using the radiometric calibrations made at the NSLS agree with this hypothesis. High-purity, single-crystal, chemical vapor deposited (CVD) diamond samples are compared to natural type-IIa PCDs and show promising high resistivity effects, the corollary of which preliminary results show is a slower response time.

8. The thermal conductivity of rock under hydrothermal conditions: measurements and applications

SciTech Connect

Williams, Colin F.; Sass, John H.

1996-01-24

The thermal conductivities of most major rock-forming minerals vary with both temperature and confining pressure, leading to substantial changes in the thermal properties of some rocks at the high temperatures characteristic of geothermal systems. In areas with large geothermal gradients, the successful use of near-surface heat flow measurements to predict temperatures at depth depends upon accurate corrections for varying thermal conductivity. Previous measurements of the thermal conductivity of dry rock samples as a function of temperature were inadequate for porous rocks and susceptible to thermal cracking effects in nonporous rocks. We have developed an instrument for measuring the thermal conductivity of water-saturated rocks at temperatures from 20 to 350 °C and confining pressures up to 100 MPa. A transient line-source of heat is applied through a needle probe centered within the rock sample, which in turn is enclosed within a heated pressure vessel with independent controls on pore and confining pressure. Application of this technique to samples of Franciscan graywacke from The Geysers reveals a significant change in thermal conductivity with temperature. At reservoir-equivalent temperatures of 250 °C, the conductivity of the graywacke decreases by approximately 25% relative to the room temperature value. Where heat flow is constant with depth within the caprock overlying the reservoir, this reduction in conductivity with temperature leads to a corresponding increase in the geothermal gradient. Consequently, reservoir temperature are encountered at depths significantly shallower than those predicted by assuming a constant temperature gradient with depth. We have derived general equations for estimating the thermal conductivity of most metamorphic and igneous rocks and some sedimentary rocks at elevated temperature from knowledge of the room temperature thermal conductivity. Application of these equations to geothermal exploration should improve estimates

9. Printed-Circuit Tape Measures For X-Ray Inspections

NASA Technical Reports Server (NTRS)

Sullivan, John E., Jr.

1990-01-01

Known pattern impressed on x-ray image for reference. Tapes made by flexible-printed-circuit technology provides identification and position references for x-ray images of weld joints. Proposed tapes consist of etched copper patterns on flexible substrates. X-rays record pattern of tape on film beneath butt-welded panels. Pattern becomes convenient reference for analysis and digitization of x-ray image.

10. Conductivity Measurements of Synthesized Heteropoly Acid Membranes for Proton Exchange Membrane Fuel Cells

SciTech Connect

Record, K.A.; Haley, B.T.; Turner, J.

2006-01-01

Fuel cell technology is receiving attention due to its potential to be a pollution free method of electricity production when using renewably produced hydrogen as fuel. In a Proton Exchange Membrane (PEM) fuel cell H2 and O2 react at separate electrodes, producing electricity, thermal energy, and water. A key component of the PEM fuel cell is the membrane that separates the electrodes. DuPont’s Nafion® is the most commonly used membrane in PEM fuel cells; however, fuel cell dehydration at temperatures near 100°C, resulting in poor conductivity, is a major hindrance to fuel cell performance. Recent studies incorporating heteropoly acids (HPAs) into membranes have shown an increase in conductivity and thus improvement in performance. HPAs are inorganic materials with known high proton conductivities. The primary objective of this work is to measure the conductivity of Nafion, X-Ionomer membranes, and National Renewable Energy Laboratory (NREL) Developed Membranes that are doped with different HPAs at different concentrations. Four-point conductivity measurements using a third generation BekkTech conductivity test cell are used to determine membrane conductivity. The effect of multiple temperature and humidification levels is also examined. While the classic commercial membrane, Nafion, has a conductivity of approximately 0.10 S/cm, measurements for membranes in this study range from 0.0030 – 0.58 S/cm, depending on membrane type, structure of the HPA, and the relative humidity. In general, the X-ionomer with H6P2W21O71 HPA gave the highest conductivity and the Nafion with the 12-phosphotungstic (PW12) HPA gave the lowest. The NREL composite membranes had conductivities on the order of 0.0013 – 0.025 S/cm.

11. Uncertainty analysis on the design of thermal conductivity measurement by a guarded cut-bar technique

Xing, Changhu; Jensen, Colby; Ban, Heng; Phillips, Jeffrey

2011-07-01

A technique adapted from the guarded-comparative-longitudinal heat flow method was selected for the measurement of the thermal conductivity of a nuclear fuel compact over a temperature range characteristic of its usage. This technique fulfills the requirement for non-destructive measurement of the composite compact. Although numerous measurement systems have been created based on the guarded-comparative method, comprehensive systematic (bias) and measurement (precision) uncertainty associated with this technique have not been fully analyzed. In addition to the geometric effect in the bias error, which has been analyzed previously, this paper studies the working condition which is another potential error source. Using finite element analysis, this study showed the effect of these two types of error sources in the thermal conductivity measurement process and the limitations in the design selection of various parameters by considering their effect on the precision error. The results and conclusions provide valuable reference for designing and operating an experimental measurement system using this technique.

12. Free-Electron X-Ray Laser Measurements of Collisional-Damped Plasmons in Isochorically Heated Warm Dense Matter

Sperling, P.; Gamboa, E. J.; Lee, H. J.; Chung, H. K.; Galtier, E.; Omarbakiyeva, Y.; Reinholz, H.; Röpke, G.; Zastrau, U.; Hastings, J.; Fletcher, L. B.; Glenzer, S. H.

2015-09-01

We present the first highly resolved measurements of the plasmon spectrum in an ultrafast heated solid. Multi-keV x-ray photons from the Linac Coherent Light Source have been focused to one micrometer diameter focal spots producing solid density aluminum plasmas with a known electron density of ne=1.8 ×1023 cm-3 . Detailed balance is observed through the intensity ratio of up- and down-shifted plasmons in x-ray forward scattering spectra measuring the electron temperature. The plasmon damping is treated by electron-ion collision models beyond the Born approximation to determine the electrical conductivity of warm dense aluminum.

13. Specific conductance measurements in central and western New York streams - A retrospective characterization

USGS Publications Warehouse

Kappel, William M.; Sinclair, Gaylen J.; Reddy, James E.; Eckhardt, David A.; deVries, M. Peter; Phillips, Margaret E.

2012-01-01

U.S. Geological Survey (USGS) Data Rescue Program funds were used to recover data from paper records for 139 streamgages across central and western New York State; 6,133 different streamflow measurement forms, collected between 1970-80, contained field water-quality measurements. The water-quality data were entered, reviewed, and uploaded into the USGS National Water Information System. In total, 4,285 unique site visits were added to the database. The new values represent baseline water quality from which to measure change and will lead to a comparison of water-quality change over the last 40 years and into the future. Specific conductance was one of the measured properties and represents a simple way to determine if ambient inorganic water quality has been altered by anthropogenic (road salt runoff, wastewater discharges, or natural gas development) or natural sources. The objective of this report is to describe ambient specific conductance characteristics of surface water across the central and western part of New York. This report presents median specific conductance of stream discharge for the period 1970-80 and a description of the relation between specific conductance and concentrations of total dissolved solids (TDS) retrieved from the USGS National Water Information System (NWIS) database from 1955 to present. The data descriptions provide a baseline of surface-water specific conductance data that can used for comparison to current and future measurements in New York streams.

14. Temperature dependent electrical conductivity measurement of Qn-(TCNQ)2 grown by different methods

2013-06-01

We measured the temperature dependent electrical conductivity on single crystal of charge transfer complex (CTC), Qn-(TCNQ)2 grown by different methods. Where, Qn and TCNQ are representing qunolinium and tetracyanoquinodimethane. The room temperature conductivity is found 100 ohm-1 cm-1 with activation energy 0.021 eV in the sample grown by electrochemical method. Whereas it is found 22 ohm-1 cm-1 with activation energy 0.026 eV for the sample grown by solution growth method. In all conductivity measurements, the observations are carried out along high conducting chain direction, which happens to be needle direction of the single crystal and known as a-direction.

15. Experimental measurement of the plasma conductivity of Z93 and Z93P thermal control paint

NASA Technical Reports Server (NTRS)

Hillard, G. Barry

1993-01-01

Two samples each of Z93 and Z93P thermal control paint were exposed to a simulated space environment in a plasma chamber. The samples were biased through a series of voltages ranging from -200 volts to +300 volts and electron and ion currents measured. By comparing the currents to those of pure metal samples of the same size and shape, the conductivity of the samples was calculated. Measured conductivity was dependent on the bias potential in all cases. For Z93P, conductivity was approximately constant over much of the bias range and we find a value of 0.5 micro-mhos per square meter for both electron and ion current. For Z93, the dependence on bias was much more pronounced but conductivity can be said to be approximately one order of magnitude larger. In addition to presenting these results, this report documents all of the experimental data as well as the statistical analyses performed.

16. Experimental Measurement and Numerical Modeling of the Effective Thermal Conductivity of TRISO Fuel Compacts

SciTech Connect

Folsom, Charles; Xing, Changhu; Jensen, Colby; Ban, Heng; Marshall, Douglas W.

2015-03-01

Accurate modeling capability of thermal conductivity of tristructural-isotropic (TRISO) fuel compacts is important to fuel performance modeling and safety of Generation IV reactors. To date, the effective thermal conductivity (ETC) of tristructural-isotropic (TRISO) fuel compacts has not been measured directly. The composite fuel is a complicated structure comprised of layered particles in a graphite matrix. In this work, finite element modeling is used to validate an analytic ETC model for application to the composite fuel material for particle-volume fractions up to 40%. The effect of each individual layer of a TRISO particle is analyzed showing that the overall ETC of the compact is most sensitive to the outer layer constituent. In conjunction with the modeling results, the thermal conductivity of matrix-graphite compacts and the ETC of surrogate TRISO fuel compacts have been successfully measured using a previously developed measurement system. The ETC of the surrogate fuel compacts varies between 50 and 30 W m-1 K-1 over a temperature range of 50-600°C. As a result of the numerical modeling and experimental measurements of the fuel compacts, a new model and approach for analyzing the effect of compact constituent materials on ETC is proposed that can estimate the fuel compact ETC with approximately 15-20% more accuracy than the old method. Using the ETC model with measured thermal conductivity of the graphite matrix-only material indicate that, in the composite form, the matrix material has a much greater thermal conductivity, which is attributed to the high anisotropy of graphite thermal conductivity. Therefore, simpler measurements of individual TRISO compact constituents combined with an analytic ETC model, will not provide accurate predictions of overall ETC of the compacts emphasizing the need for measurements of composite, surrogate compacts.

17. Rolling ball algorithm as a multitask filter for terrain conductivity measurements

Rashed, Mohamed

2016-09-01

Portable frequency domain electromagnetic devices, commonly known as terrain conductivity meters, have become increasingly popular in recent years, especially in locating underground utilities. Data collected using these devices, however, usually suffer from major problems such as complexity and interference of apparent conductivity anomalies, near edge local spikes, and fading of conductivity contrast between a utility and the surrounding soil. This study presents the experience of adopting the rolling ball algorithm, originally designed to remove background from medical images, to treat these major problems in terrain conductivity measurements. Applying the proposed procedure to data collected using different terrain conductivity meters at different locations and conditions proves the capability of the rolling ball algorithm to treat these data both efficiently and quickly.

18. D0 Silicon Upgrade: Thermal Conductivity Measurements of Adhesives and Metal Strips

SciTech Connect

Jostlein, H.; Schmidgall, N.; /Fermilab

1995-08-10

This note is a followup to previous work done relating to thermal conductivity tests for the DO Silicon Upgrade. The testing of adhesives described here was done as outlined in the above mentioned note; therefore, the experimental setup and design for testing adhesives is marginally described here. However, some strips were tested to determine their thermal conductivity which utilized a different testing setup. That setup is described here as well. The measured thermal conductivities of the adhesives show Ablefilm 563K to have the highest thermal conductivity value of 0.89 W/m-K. The strip tests also showed that a consistent thermal conductivity value can be obtained for a strip within 5%.

19. In situ electrical conductivity measurements of H2O under static pressure up to 28 GPa

Liu, Bao; Gao, Yang; Han, Yonghao; Ma, Yanzhang; Gao, Chunxiao

2016-08-01

The in situ electrical conductivity measurements on water in both solid state and liquid state were performed under pressure up to 28 GPa and temperature from 77 K to 300 K using a microcircuit fabricated on a diamond anvil cell (DAC). Water chemically ionization mainly contributes to electrical conduction in liquid state, which is in accord with the results obtained under dynamic pressure. Energy band theory of liquid water was used to understand effect of static pressure on electrical conduction of water. The electric conductivity of H2O decreased discontinuously by four orders of magnitude at 0.7-0.96 GPa, indicating water frozen at this P-T condition. Correspondingly, the conduction of H2O in solid state is determined by arrangement and bending of H-bond in ice VI and ice VII. Based on Jaccard theory, we have concluded that the charge carriers of ice are already existing ions and Bjerrum defects.

20. Incoherent scatter measurements of E region conductivities and currents in the auroral zone

NASA Technical Reports Server (NTRS)

Brekke, A.; Doupnik, J. R.; Banks, P. M.

1974-01-01

Data taken by incoherent scatter radar have been used to investigate ionospheric conductivities and electrical currents. During quiet days, the conductivities appear to vary in a way consistent with ionization arising from solar EUV radiation. In the evening hours, enhancements in the northward electric field are found to precede small increases in the conductivities. Strong enhancements of the Hall conductivity relative to the Pedersen conductivity occur during negative bays when the electric field is in a southwestward direction. The ionospheric currents calculated in the geomagnetic east-west direction are in good agreement with the H component measured by a nearby magnetometer; this result indicates that the current causing the ground level magnetic fluctuations is a broad horizontal sheet current. The north-south ionospheric current, however, consistently disagrees with the observed D component in a manner that cannot easily be explained unless currents parallel to the earth's magnetic field are present.

1. Factors influencing in situ gamma-ray measurements

Loonstra, E. H.; van Egmond, F. M.

2009-04-01

Introduction In situ passive gamma-ray sensors are very well suitable for mapping physical soil properties. In order to make a qualitative sound soil map, high quality input parameters for calibration are required. This paper will focus on the factors that affect the output of in situ passive gamma-ray sensors, the primary source, soil, not taken into account. Factors The gamma-ray spectrum contains information of naturally occurring nuclides 40K, 238U and 232Th and man-made nuclides like 137Cs, as well as the total count rate. Factors that influence the concentration of these nuclides and the count rate can be classified in 3 categories. These are sensor design, environmental conditions and operational circumstances. Sensor design The main elements of an in situ gamma-ray sensor that influence the outcome and quality of the output are the crystal and the spectrum analysis method. Material and size of the crystal determine the energy resolution. Though widely used, NaI crystals are not the most efficient capturer of gamma radiation. Alternatives are BGO and CsI. BGO has a low peak resolution, which prohibits use in cases where man-made nuclides are subject of interest. The material is expensive and prone to temperature instability. CsI is robust compared to NaI and BGO. The density of CsI is higher than NaI, yielding better efficiency, especially for smaller crystal sizes. More volume results in higher energy efficiency. The reduction of the measured spectral information into concentration of radionuclides is mostly done using the Windows analysis method. In Windows, the activities of the nuclides are found by summing the intensities of the spectrum found in a certain interval surrounding a peak. A major flaw of the Windows method is the limited amount of spectral information that is incorporated into the analysis. Another weakness is the inherent use of ‘stripping factors' to account for contributions of radiation from nuclide A into the peak of nuclide B. This

2. The blood beat measurement with near infrared ray

Oshiro, Osamu; Horio, Hideyuki; Masuda, Yasushi

This paper describes the blood beat measurement system with near infra-red ray. A blood vessel was captured sequentially with a CCD camera, an near infra-red LED and an optical filter. In order to extract a blood vessel portion from each captured image, binarization processing was performed using the threshold on the basis of the first captured image. For the reduction of the error caused by the subject's hand slight movement, the position adjustment was performed with the landmark, which was found with skeltonizing and extracting the diverging point. The pixel number of the blood vessel portion was counted and the thickness of the blood vessel was analyzed by performing a Fourier analysis. The Fourier analysis shows the peak at the frequency of 1.4 Hz corresponding to 84 beat count in a minute. For the evaluation of the proposed method, blood beat was measured with a sphygmomanometer simultaneously. As the results, the almost same pulse rate could be obtained from both method. These results indicate that the method has the possibility to count a pulse.

3. The thermal conductivity of rock under hydrothermal conditions: Measurements and applications

SciTech Connect

Williams, C.F.; Sass, J.H.

1996-12-31

The thermal conductivities of most major rock-forming minerals vary with both temperature and confining pressure, leading to substantial changes in the thermal properties of some rocks at the high temperatures characteristic of geothermal systems. In areas with large geothermal gradients, the successful use of near-surface heat flow measurements to predict temperatures at depth depends upon accurate corrections for varying thermal conductivity. Previous measurements of the thermal conductivity of dry rock samples as a function of temperature were inadequate for porous rocks and susceptible to thermal cracking effects m nonporous rocks. We have developed an instrument for measuring the thermal conductivity of water-saturated rocks at temperatures from 20 to 350{degrees}C and confining pressures up to 100 MPa. A transient line-source of heat is applied through a needle probe centered within the rock sample, which in turn is enclosed within a heated pressure vessel with independent controls on pore and confining pressure. Application of this technique to samples of Franciscan graywacke from The Geysers reveals a significant change in thermal conductivity with temperature. At reservoir-equivalent temperatures of 250{degrees}C, the conductivity of the graywacke decreases by approximately 25 % relative to the room temperature value. Where heat how is constant with depth within the caprock overlying the reservoir, this reduction in conductivity with temperature leads to a corresponding increase in the geothermal gradient. Consequently, reservoir temperatures are encountered at depths significantly shallower than those predicted by assuming a constant temperature gradient with depth. We have derived general equations for estimating the thermal conductivity of most metamorphic and igneous rocks and some sedimentary rocks at elevated temperature from knowledge of the room temperature thermal conductivity.

4. Quality control measurements for digital x-ray detectors.

PubMed

Marshall, N W; Mackenzie, A; Honey, I D

2011-02-21

This paper describes a digital radiography (DR) quality control protocol for DR detectors from the forthcoming report from the Institute of Physics and Engineering in Medicine (IPEM). The protocol was applied to a group of six identical caesium iodide (CsI) digital x-ray detectors to assess reproducibility of methods, while four further detectors were assessed to examine the wider applicability. Twelve images with minimal spatial frequency processing are required, from which the detector response, lag, modulation transfer function (MTF), normalized noise power spectrum (NNPS) and threshold contrast-detail (c-d) detectability are calculated. The x-ray spectrum used was 70 kV and 1 mm added copper filtration, with a target detector air kerma of 2.5 µGy for the NNPS and c-d results. In order to compare detector performance with previous imaging technology, c-d data from four screen/film systems were also acquired, at a target optical density of 1.5 and an average detector air kerma of 2.56 µGy. The DR detector images were typically acquired in 20 min, with a further 45 min required for image transfer and analysis. The average spatial frequency for the 50% point of the MTF for six identical detectors was 1.29 mm(-1) ± 0.05 (3.9% coefficient of variation (cov)). The air kerma set for the six systems was 2.57 µGy ± 0.13 (5.0% cov) and the NNPS at this air kerma was 1.42 × 10(-5) mm(2) (6.5% cov). The detective quantum efficiency (DQE) measured for the six identical detectors was 0.60 at 0.5 mm(-1), with a maximum cov of 10% at 2.9 mm(-1), while the average DQE was 0.56 at 0.5 mm(-1) for three CsI detectors from three different manufacturers. Comparable c-d performance was found for these detectors (5.9% cov) with an average threshold contrast of 0.46% for 11 mm circular discs. The average threshold contrast for the S/F systems was 0.70% at 11 mm, indicating superior imaging performance for the digital systems. The protocol was found to be quick, reproducible and

5. Quality control measurements for digital x-ray detectors

Marshall, N. W.; Mackenzie, A.; Honey, I. D.

2011-02-01

This paper describes a digital radiography (DR) quality control protocol for DR detectors from the forthcoming report from the Institute of Physics and Engineering in Medicine (IPEM). The protocol was applied to a group of six identical caesium iodide (CsI) digital x-ray detectors to assess reproducibility of methods, while four further detectors were assessed to examine the wider applicability. Twelve images with minimal spatial frequency processing are required, from which the detector response, lag, modulation transfer function (MTF), normalized noise power spectrum (NNPS) and threshold contrast-detail (c-d) detectability are calculated. The x-ray spectrum used was 70 kV and 1 mm added copper filtration, with a target detector air kerma of 2.5 µGy for the NNPS and c-d results. In order to compare detector performance with previous imaging technology, c-d data from four screen/film systems were also acquired, at a target optical density of 1.5 and an average detector air kerma of 2.56 µGy. The DR detector images were typically acquired in 20 min, with a further 45 min required for image transfer and analysis. The average spatial frequency for the 50% point of the MTF for six identical detectors was 1.29 mm-1 ± 0.05 (3.9% coefficient of variation (cov)). The air kerma set for the six systems was 2.57 µGy ± 0.13 (5.0% cov) and the NNPS at this air kerma was 1.42 × 10-5 mm2 (6.5% cov). The detective quantum efficiency (DQE) measured for the six identical detectors was 0.60 at 0.5 mm-1, with a maximum cov of 10% at 2.9 mm-1, while the average DQE was 0.56 at 0.5 mm-1 for three CsI detectors from three different manufacturers. Comparable c-d performance was found for these detectors (5.9% cov) with an average threshold contrast of 0.46% for 11 mm circular discs. The average threshold contrast for the S/F systems was 0.70% at 11 mm, indicating superior imaging performance for the digital systems. The protocol was found to be quick, reproducible and gave an in

6. Interpretation of rapid rises in hard X-rays and microwaves with the thermal conduction front model

NASA Technical Reports Server (NTRS)

Batchelor, D. A.

1986-01-01

Impulsive hard X-ray and microwave bursts with rise times from 0.1 to 10 seconds are discussed. Source areas calculated by the method of Crannell et al. (1978) were compared with source areas determined from Hinotori and the Hard X-ray Imaging Spectrometer (HXIS) images. The agreement strongly suggests that the method is valid. If the thermal conduction front model for the hard X-ray and microwave source is adopted, then the method enables derivation of area, density, magnetic field, and rise time from hard X-ray and microwave spectral observations. This approach was used to derive these parameters for several rapid impulsive rises in the flares of July 1, 1980, and May 21, 1984. It is shown that the model provides a consistent interpretation of the observations of these impulsive increases. Indeed, the model provides a way to calculate rise times from spectra alone (to within a factor of about three) over more than two orders of magnitude.

7. Thermal conductivity measurement in clay dominant consolidated material by Transient Hot-Wire method.

Garnier, J. P.; Gallier, J.; Mercx, B.; Dudoignon, P.; Milcent, D.

2010-06-01

The transient hot-wire (THW) technique is widely used for measurements of the thermal-conductivity of most fluids and some attempts have also been carried out for simultaneous measurements of the thermal-diffusivity with the same hot wire. This technique was also tried to determine thermal properties of soils by the mean of probes which can be considered as wire with some assumptions. The purpose of this paper is to validate the thermal conductivity measurement by the THW technique in geomaterials, composed of compacted sand + clay mineral that can be used for earth construction (Compacted Earth Brick). The thermal transfer behaviors are mainly governed by the texture and moisture of the geomaterials. Thus the investigations were performed (1) in media made of glass beads of different diameters in dry and saturated state in order to observe the role of grain sizes and saturation state on the wire temperature (Δt) measurements and (2) in the compacted clay-geomaterial at different moisture states. The Δt / ln(t) diagrams allow the calculation of two thermal conductivities. The first one, measured in the short time acquisition (< 1s), characterizes the microtexture of the material and its hydrated state. The second one, measured for longer time acquisitions, characterizes the mean thermal conductivity of the material.

8. Improvements in 3-omega measurement of thermal conductivity for nanostructured materials

Zhou, Chuanle; Grayson, M.; Koblmueller, G.

2011-03-01

Nanostructured materials have reduced thermal conductivity in order to enhance the thermoelectric figure of merit (ZT). The 3 ω method is widely used for vertical thermal conductivity measurements in the nanostructure materials, especially layered materials. The challenge for this method is to measure the small 3 ω voltage at the third harmonic, above the comparably large ω voltage from the sample at the fundamental frequency, complicated by the nonlinear signal from other components in the measurement circuit. We carefully study the 3 ω method [Cahill, Rev. Sci. lnstrum. 61 (2), 802 (1990)] and develop a strategy to increase the signal to noise ratio of the data, for more accurate results. We also investigate an alternate sample preparation geometry for the 3 ω measurement, so that the heat flow is vertical and linear through the thin film instead of cylindrical as is standard for this method. This results in a direct measurement of the vertical thermal conductivity in such an anisotropic material. New geometries for measuring lateral thermal conductivity will also be proposed and explored.

9. PCB glass-fibre laminates: Thermal conductivity measurements and their effect on simulation

Sarvar, F.; Poole, N. J.; Witting, P. A.

1990-12-01

Accurate values of thermal conductivity are required for the simulation of temperature phenomena in electronic circuits. This paper presents the results of measurements carried out to determine the thermal conductivity along and normal to the plane of fibre glass laminates used in the manufacture of printed circuit boards. It has been found that the reinforced fibre-glass substrates used in PCBs are strongly anisotropic with the conductivity normal to the boards being much smaller than tangential to it. The test samples were type FR4 epoxy/glass laminates. An experiment has been designed which determines the thermal conductivity in-the-plane of the laminates by matching the measured temperature distribution along a heated specimen with a finite difference solution. An electrically heated Lees’ disc apparatus is also used to measure the thermal conductivity of these boards in a direction normal to their plane. The samples tested yielded values of 0.343 W/mK and 1.059 W/mK for thermal conductivity through and along the plane of the boards, respectively.

10. Thermal conductivity measurements in Porous mixtures of methane hydrate and quartz sand

USGS Publications Warehouse

Waite, W.F.; deMartin, B.J.; Kirby, S.H.; Pinkston, J.; Ruppel, C.D.

2002-01-01

Using von Herzen and Maxwell's needle probe method, we measured thermal conductivity in four porous mixtures of quartz sand and methane gas hydrate, with hydrate composing 0, 33, 67 and 100% of the solid volume. Thermal conductivities were measured at a constant methane pore pressure of 24.8 MPa between -20 and +15??C, and at a constant temperature of -10??C between 3.5 and 27.6 MPa methane pore pressure. Thermal conductivity decreased with increasing temperature and increased with increasing methane pore pressure. Both dependencies weakened with increasing hydrate content. Despite the high thermal conductivity of quartz relative to methane hydrate, the largest thermal conductivity was measured in the mixture containing 33% hydrate rather than in hydrate-free sand. This suggests gas hydrate enhanced grain-to-grain heat transfer, perhaps due to intergranular contact growth during hydrate synthesis. These results for gas-filled porous mixtures can help constrain thermal conductivity estimates in porous, gas hydrate-bearing systems.

11. Microengineered Conductive Elastomeric Electrodes for Long-Term Electrophysiological Measurements with Consistent Impedance under Stretch

PubMed Central

Hu, Dinglong; Cheng, Tin Kei; Xie, Kai; Lam, Raymond H. W.

2015-01-01

In this research, we develop a micro-engineered conductive elastomeric electrode for measurements of human bio-potentials with the absence of conductive pastes. Mixing the biocompatible polydimethylsiloxane (PDMS) silicone with other biocompatible conductive nano-particles further provides the material with an electrical conductivity. We apply micro-replica mold casting for the micro-structures, which are arrays of micro-pillars embedded between two bulk conductive-PDMS layers. These micro-structures can reduce the micro-structural deformations along the direction of signal transmission; therefore the corresponding electrical impedance under the physical stretch by the movement of the human body can be maintained. Additionally, we conduct experiments to compare the electrical properties between the bulk conductive-PDMS material and the microengineered electrodes under stretch. We also demonstrate the working performance of these micro-engineered electrodes in the acquisition of the 12-lead electrocardiographs (ECG) of a healthy subject. Together, the presented gel-less microengineered electrodes can provide a more convenient and stable bio-potential measurement platform, making tele-medical care more achievable with reduced technical barriers for instrument installation performed by patients/users themselves. PMID:26512662

12. Microengineered Conductive Elastomeric Electrodes for Long-Term Electrophysiological Measurements with Consistent Impedance under Stretch.

PubMed

Hu, Dinglong; Cheng, Tin Kei; Xie, Kai; Lam, Raymond H W

2015-01-01

In this research, we develop a micro-engineered conductive elastomeric electrode for measurements of human bio-potentials with the absence of conductive pastes. Mixing the biocompatible polydimethylsiloxane (PDMS) silicone with other biocompatible conductive nano-particles further provides the material with an electrical conductivity. We apply micro-replica mold casting for the micro-structures, which are arrays of micro-pillars embedded between two bulk conductive-PDMS layers. These micro-structures can reduce the micro-structural deformations along the direction of signal transmission; therefore the corresponding electrical impedance under the physical stretch by the movement of the human body can be maintained. Additionally, we conduct experiments to compare the electrical properties between the bulk conductive-PDMS material and the microengineered electrodes under stretch. We also demonstrate the working performance of these micro-engineered electrodes in the acquisition of the 12-lead electrocardiographs (ECG) of a healthy subject. Together, the presented gel-less microengineered electrodes can provide a more convenient and stable bio-potential measurement platform, making tele-medical care more achievable with reduced technical barriers for instrument installation performed by patients/users themselves. PMID:26512662

13. A New Guarded Hot Plate Designed for Thermal-Conductivity Measurements at High Temperature

Scoarnec, V.; Hameury, J.; Hay, B.

2015-03-01

The Laboratoire National de Métrologie et d'Essais has developed a new guarded hot-plate apparatus operating from to in the thermal-conductivity range from to . This facility has been specifically designed for measuring medium thermal-conductivity materials at high temperature on square specimens (100 mm side), which are easier to machine than circular ones. The hot plate and cold plates are similar with a metering section independent from the guard ring. The specimens are laterally isolated by an air gap of 4 mm width and can be instrumented by temperature sensors in order to reduce effects of thermal contact resistances between the specimens and the heating plates. Measurements have been performed on certified reference materials and on "calibrated" materials. Relative deviations between thermal conductivities measured and reference values are less than 5 % in the operating range.

14. High-precision micropipette thermal sensor for measurement of thermal conductivity of carbon nanotubes thin film

Shrestha, Ramesh

The thesis describes novel glass micropipette thermal sensor fabricated in cost-effective manner and thermal conductivity measurement of carbon nanotubes (CNT) thin film using the developed sensor. Various micrometer-sized sensors, which range from 2 microm to 30 microm, were produced and tested. The capability of the sensor in measuring thermal fluctuation at micro level with an estimated resolution of +/-0.002°C is demonstrated. The sensitivity of sensors was recorded from 3.34 to 8.86 microV/°C, which is independent of tip size and dependent on the coating of Nickel. The detailed experimental setup for thermal conductivity measurement of CNT film is discussed and 73.418 W/m°C was determined as the thermal conductivity of the CNT film at room temperature.

15. X-ray Thomson scattering measurements from shock-compressed deuterium

Davis, P.; Doeppner, T.; Rygg, J. R.; Fortmann, C.; Unites, W.; Salmonson, J.; Collins, G. W.; Landen, O. L.; Falcone, R. W.; Glenzer, S. H.

2012-05-01

X-ray Thomson scattering has recently been shown to be an effective method of diagnosing a variety of high energy density plasma conditions. We apply this powerful technique to the widely studied problem of shock-compressed liquid deuterium. The behavior of deuterium under extreme conditions has received considerable attention due to its central role in models of giant planets and the importance of the high-pressure insulator-metal transition. We have used spectrally resolved x-ray scattering from electron-plasma waves to perform microscopic observations of ionization during compression. In these experiments, a single shock was launched in cryogenic deuterium reaching compressions of 3x. The 2 keV Ly-α line in silicon was used as an x-ray source in a forward scattering geometry. In addition to elastic scattering from tightly bound electrons, this low probe energy accessed the collective plasmon oscillations of delocalized electrons. Inelastic scattering from the plasmons allowed accurate measurements of the free electron density through the spectral position of the resonance and provided an estimate of the temperature through its ratio with the elastic feature. Combined with velocity interferometry from the reflective shock front, this lead to a direct determination of the ionization state. We compare the measured ionization conditions with computational models. Additionally, we discuss the possibility of using this technique to determine electrical conductivity and to directly observe pressure-induced molecular dissociation along the Hugoniot.

16. X-ray Thomson scattering measurements from shock-compressed deuterium

SciTech Connect

Davis, P.; Doeppner, T.; Rygg, J. R.; Fortmann, C.; Unites, W.; Salmonson, J.; Collins, G. W.; Landen, O. L.; Falcone, R. W.; Glenzer, S. H.

2012-05-25

X-ray Thomson scattering has recently been shown to be an effective method of diagnosing a variety of high energy density plasma conditions. We apply this powerful technique to the widely studied problem of shock-compressed liquid deuterium. The behavior of deuterium under extreme conditions has received considerable attention due to its central role in models of giant planets and the importance of the high-pressure insulator-metal transition. We have used spectrally resolved x-ray scattering from electron-plasma waves to perform microscopic observations of ionization during compression. In these experiments, a single shock was launched in cryogenic deuterium reaching compressions of 3x. The 2 keV Ly-{alpha} line in silicon was used as an x-ray source in a forward scattering geometry. In addition to elastic scattering from tightly bound electrons, this low probe energy accessed the collective plasmon oscillations of delocalized electrons. Inelastic scattering from the plasmons allowed accurate measurements of the free electron density through the spectral position of the resonance and provided an estimate of the temperature through its ratio with the elastic feature. Combined with velocity interferometry from the reflective shock front, this lead to a direct determination of the ionization state. We compare the measured ionization conditions with computational models. Additionally, we discuss the possibility of using this technique to determine electrical conductivity and to directly observe pressure-induced molecular dissociation along the Hugoniot.

17. Inelastic x-ray scattering measurements of phonon dynamics in URu2Si2

DOE PAGESBeta

Gardner, D. R.; Bonnoit, C. J.; Chisnell, R.; Said, A. H.; Leu, B. M.; Williams, Travis J.; Luke, G. M.; Lee, Y. S.

2016-02-11

In this paper, we study high-resolution inelastic x-ray scattering measurements of the acoustic phonons of URu2Si2. At all temperatures, the longitudinal acoustic phonon linewidths are anomalously broad at small wave vectors revealing a previously unknown anharmonicity. The phonon modes do not change significantly upon cooling into the hidden order phase. In addition, our data suggest that the increase in thermal conductivity in the hidden order phase cannot be driven by a change in phonon dispersions or lifetimes. Hence, the phonon contribution to the thermal conductivity is likely much less significant compared to that of the magnetic excitations in the lowmore » temperature phase.« less

18. BRINE Distribution in Harite Rocks-Inference from Measured Electrical CONDUCTIVITY-

Kitano, M.; Watanabe, T.

2013-12-01

Intercrystalline fluid can significantly affect rheological and transport properties of rocks. Its influences are strongly depended on its distribution. The dihedral angle between solid and liquid phases has been widely accepted as a key parameter that controls solid-liquid textures. The liquid phase is not expected to be interconnected if the dihedral angle is larger than 60°. However, observations contradictory to dihedral angle values have been reported. Watanabe (2010) suggested that the grain boundary fluid coexist with a positive dihedral angle. Similar thin fluid films might exist in grain boundaries of crustal rocks, and play important roles in crustal processes. In order to understand the nature of this fluid, we have studied the distribution of brine in halite rocks through measurements of conductivity. A sample was prepared by cold-pressing (the axial stress of 140MPa, 40minutes) and annealing (the temperature of 160°C and 180MPa confining pressure for about 160hours) of wet NaCl powder. During annealing, conductivity of a sample was monitored (2-electrode method) to reach a quasi-stationary value. The volume fraction of water is estimated to be 0.1×0.01% based on the FTIR measurement. Grains are polygonal and their diameters are ~100 μm. The cylindrical (D=9mm, L=3mm) surface of an annealed sample was weakly dried and coated with RTV rubber to suppress the conduction on the surface. Conductivity measurements were made at various pressure and temperature conditions(P<180 MPa, T<180°C). The dihedral angle of NaCl-water system is 66° at P=30MPa and T=30°C, and it becomes smaller than 60° at high pressure and temperature conditions(Holness & Lewis, 1997). Measured conductivity was of the order of 10-7~10-9 (S/m). When the temperature was fixed, a lower conductivity was observed for a higher pressure. The decrease in conductivity was typically 50% for the increase in pressure of 30MPa. For a given pressure, the conductivity increased with increasing

19. Inductive Measurement of Plasma Jet Electrical Conductivity (MSFC Center Director's discretionary Fund). Part 2

NASA Technical Reports Server (NTRS)

Turner, M. W.; Hawk, C. W.; Litchford, R. J.

2001-01-01

Measurement of plasma jet electrical conductivity has utility in the development of explosively driven magnetohydrodynamic (MHD) energy converters as well as magnetic flux compression reaction chambers for nuclear/chemical pulse propulsion and power. Within these types of reactors, the physical parameter of critical importance to underlying MHD processes is the magnetic Reynolds number, the value of which depends upon the product of plasma electrical conductivity and velocity. Therefore, a thorough understanding of MHD phenomena at high magnetic Reynolds number is essential, and methods are needed for the accurate and reliable measurement of electrical conductivity in high-speed plasma jets. It is well known that direct measurements using electrodes suffer from large surface resistance, and an electrodeless technique is desired. To address this need, an inductive probing scheme, originally developed for shock tube studies, has been adapted. In this method, the perturbation of an applied magnetic field by a plasma jet induces a voltage in a search coil, which, in turn, can be used to infer electrical conductivity through the inversion of a Fredholm integral equation of the first kind. A 1-in.-diameter probe using a light-gas gun. Exploratory laboratory experiments were carried out using plasma jets expelled from 15-g shaped charges. Measured conductivities were in the range of 4 kS/m for unseeded octol charges and 26 kS/m for seeded octol charges containing 2-percent potassium carbonate by mass.

20. An affordable and accurate conductivity probe for density measurements in stratified flows

Carminati, Marco; Luzzatto-Fegiz, Paolo

2015-11-01

In stratified flow experiments, conductivity (combined with temperature) is often used to measure density. The probes typically used can provide very fine spatial scales, but can be fragile, expensive to replace, and sensitive to environmental noise. A complementary instrument, comprising a low-cost conductivity probe, would prove valuable in a wide range of applications where resolving extremely small spatial scales is not needed. We propose using micro-USB cables as the actual conductivity sensors. By removing the metallic shield from a micro-B connector, 5 gold-plated microelectrodes are exposed and available for 4-wire measurements. These have a cell constant ~550m-1, an intrinsic thermal noise of at most 30pA/Hz1/2, as well as sub-millisecond time response, making them highly suitable for many stratified flow measurements. In addition, we present the design of a custom electronic board (Arduino-based and Matlab-controlled) for simultaneous acquisition from 4 sensors, with resolution (in conductivity, and resulting density) exceeding the performance of typical existing probes. We illustrate the use of our conductivity-measuring system through stratified flow experiments, and describe plans to release simple instructions to construct our complete system for around 200.

1. Direct measurement of thermal conductivity in solid iron at planetary core conditions

Konôpková, Zuzana; McWilliams, R. Stewart; Gómez-Pérez, Natalia; Goncharov, Alexander F.

2016-06-01

The conduction of heat through minerals and melts at extreme pressures and temperatures is of central importance to the evolution and dynamics of planets. In the cooling Earth’s core, the thermal conductivity of iron alloys defines the adiabatic heat flux and therefore the thermal and compositional energy available to support the production of Earth’s magnetic field via dynamo action. Attempts to describe thermal transport in Earth’s core have been problematic, with predictions of high thermal conductivity at odds with traditional geophysical models and direct evidence for a primordial magnetic field in the rock record. Measurements of core heat transport are needed to resolve this difference. Here we present direct measurements of the thermal conductivity of solid iron at pressure and temperature conditions relevant to the cores of Mercury-sized to Earth-sized planets, using a dynamically laser-heated diamond-anvil cell. Our measurements place the thermal conductivity of Earth’s core near the low end of previous estimates, at 18–44 watts per metre per kelvin. The result is in agreement with palaeomagnetic measurements indicating that Earth’s geodynamo has persisted since the beginning of Earth’s history, and allows for a solid inner core as old as the dynamo.

2. Direct measurement of thermal conductivity in solid iron at planetary core conditions.

PubMed

Konôpková, Zuzana; McWilliams, R Stewart; Gómez-Pérez, Natalia; Goncharov, Alexander F

2016-06-01

The conduction of heat through minerals and melts at extreme pressures and temperatures is of central importance to the evolution and dynamics of planets. In the cooling Earth's core, the thermal conductivity of iron alloys defines the adiabatic heat flux and therefore the thermal and compositional energy available to support the production of Earth's magnetic field via dynamo action. Attempts to describe thermal transport in Earth's core have been problematic, with predictions of high thermal conductivity at odds with traditional geophysical models and direct evidence for a primordial magnetic field in the rock record. Measurements of core heat transport are needed to resolve this difference. Here we present direct measurements of the thermal conductivity of solid iron at pressure and temperature conditions relevant to the cores of Mercury-sized to Earth-sized planets, using a dynamically laser-heated diamond-anvil cell. Our measurements place the thermal conductivity of Earth's core near the low end of previous estimates, at 18-44 watts per metre per kelvin. The result is in agreement with palaeomagnetic measurements indicating that Earth's geodynamo has persisted since the beginning of Earth's history, and allows for a solid inner core as old as the dynamo. PMID:27251283

3. New portable instrument for the measurement of thermal conductivity in gas process conditions

Queirós, C. S. G. P.; Lourenço, M. J. V.; Vieira, S. I.; Serra, J. M.; Nieto de Castro, C. A.

2016-06-01

The development of high temperature gas sensors for the monitoring and determination of thermophysical properties of complex process mixtures at high temperatures faces several problems, related with the materials compatibility, active sensing parts sensitivity, and lifetime. Ceramic/thin metal films based sensors, previously developed for the determination of thermal conductivity of molten materials up to 1200 °C, were redesigned, constructed, and applied for thermal conductivity measuring sensors. Platinum resistance thermometers were also developed using the same technology, to be used in the temperature measurement, which were also constructed and tested. A new data acquisition system for the thermal conductivity sensors, based on a linearization of the transient hot-strip model, including a portable electronic bridge for the measurement of the thermal conductivity in gas process conditions was also developed. The equipment is capable of measuring the thermal conductivity of gaseous phases with an accuracy of 2%-5% up to 840 °C (95% confidence level). The development of sensors up to 1200 °C, present at the core of the combustion chambers, will be done in a near future.

4. New portable instrument for the measurement of thermal conductivity in gas process conditions.

PubMed

Queirós, C S G P; Lourenço, M J V; Vieira, S I; Serra, J M; Nieto de Castro, C A

2016-06-01

The development of high temperature gas sensors for the monitoring and determination of thermophysical properties of complex process mixtures at high temperatures faces several problems, related with the materials compatibility, active sensing parts sensitivity, and lifetime. Ceramic/thin metal films based sensors, previously developed for the determination of thermal conductivity of molten materials up to 1200 °C, were redesigned, constructed, and applied for thermal conductivity measuring sensors. Platinum resistance thermometers were also developed using the same technology, to be used in the temperature measurement, which were also constructed and tested. A new data acquisition system for the thermal conductivity sensors, based on a linearization of the transient hot-strip model, including a portable electronic bridge for the measurement of the thermal conductivity in gas process conditions was also developed. The equipment is capable of measuring the thermal conductivity of gaseous phases with an accuracy of 2%-5% up to 840 °C (95% confidence level). The development of sensors up to 1200 °C, present at the core of the combustion chambers, will be done in a near future. PMID:27370495

5. Application of the Reverberation-Ray Matrix to the Non-Fourier Heat Conduction in Functionally Graded Materials

Zhou, Feng-xi

2016-02-01

The method of the reverberation-ray matrix has been developed and successfully applied to analyse the wave propagation in a multibranched framed structure or in a layered medium. However, the method is confined to the case of mechanical loads applied at the medium until now. This paper aims to extend the formulation of the reverberation-ray matrix to cases of thermal propagation and diffusion. The thermal response in functionally graded materials (FGM) with the non-Fourier heat conduction model is analysed. In the present work, it is assumed that the material properties of an FG plate vary only in the thickness direction by following the power law function. The effect of non-Fourier and material inhomogeneity in the plate subjected to a periodic thermal disturbance is investigated. The present approach is validated by comparing it with the solutions obtained by other methods.

6. Polarizabilities of Adsorbed and Assembled Molecules: Measuring the Conductance through Buried Contacts

PubMed Central

2010-01-01

We have measured the polarizabilities of four families of molecules adsorbed to Au{111} surfaces, with structures ranging from fully saturated to fully conjugated, including single-molecule switches. Measured polarizabilities increase with increasing length and conjugation in the adsorbed molecules and are consistent with theoretical calculations. For single-molecule switches, the polarizability reflects the difference in substrate−molecule electronic coupling in the ON and OFF conductance states. Calculations suggest that the switch between the two conductance states is correlated with an oxidation state change in a nitro functional group in the switch molecules. PMID:21077677

7. Measurement of the thermal conductivity of dielectric thin solid films with a thermal comparator

SciTech Connect

Amsden, C.A.; Gilman, S.E.; Jacobs, S.D.; Torok, J.S.

1988-04-01

Low thermal conductivity has important implications for electric and optical applications, where heat deposited in a thin layer must be dissipated to prevent damage. Models which account for thermal transport in thin film structures may have no predictive value if they employ bulk conductivity data. Most techniques utilized to measure the thermal conductivity of thin solid films are difficult and time consuming. The method we have developed is relatively rapid, nondestructive, and is capable of evaluating the samples in a conventional film on substrate geometry. Our thermal conductivity apparatus consists of a control and readout module, signal processing equipment, and an environmentally isolated sample chamber enclosing a sample stage. The commercial unit was converted into a high precision device by temperature controlling both the samples and the sample stage, and by performing averaging of the output signal. The thermal conductivity values obtained are below those of bulk solids. In addition, the conductivities seem to increase with increasing film thickness. Titania seems to have a higher thermal conductivity when deposited by ion-beam sputtering rather than electron-beam evaporation. Some of the electron-beam films were crazed, indicating high levels of stress. The effect of stress and crazing on thermal conductivity is not readily apparent. 11 refs., 1 fig., 1 tab.

8. The Comparison of Predicted and Measured Hydraulic Conductivities of Soils having Different Physical Properties

Zengin, Enes; Abiddin Erguler, Zeynal; Karakuş, Hüseyin

2015-04-01

Hydraulic conductivity is one of the most important parameter of earth science related studies such as engineering geology, soil physics, agriculture etc. In order to estimate the ability of soils to transport fluid through particles, field and laboratory tests have been performed since last decades of 19th century. Constant and falling head tests are widely used to directly measure hydraulic conductivity values in laboratory conditions for soils having different particle size distributions. The determination of hydraulic conductivity of soils by performing these methods are time consuming processes and also requires undisturbed samples to reflect in-situ natural condition. Considering these limitations, numerous approaches have been proposed to practically estimate hydraulic conductivity of soils by utilizing empirical equations based on simple physical and index properties such as grain size distribution curves related parameters, porosity, void ratio, etc. Many previous studies show that the hydraulic conductivity values calculated by empirical equations deviate more than two order magnitude than the measured hydraulic conductivity values obtained from convenient permeability tests. In order to investigate the main controlling parameters on hydraulic conductivity of soils, a comprehensive research program was carried out on some disturbed and undisturbed soil samples collected from different locations in Turkey. The hydraulic conductivity values of samples were determined as changing between 10-6 and 10-9 m/s by using falling head tests. In addition to these tests, basic soil properties such as natural water content, Atterberg limits, specific gravity and grain size analyses of these samples were also defined to be used as an input parameters of empirical equations for prediction hydraulic conductivity values. In addition, data from previous studies were also used for the aim of this study. The measured hydraulic conductivity values were correlated with all

9. Laboratory Thermal Conductivity Measurements in Pure Methane Hydrate Between -5 and -30 ° C

Waite, W. F.; Pinkston, J.; Kirby, S. H.

2001-12-01

Naturally occurring methane (CH4) hydrate, found extensively in shallow permafrost and continental margin sediment, has generated interest as a potential energy resource, a geohazard, and a contributor to global climate change. The significance of gas hydrate in these roles depends in part on the effects of temperature on their stability, and hence can be sensitive to exchanges of heat with their environment. Thermal properties such as conductivity and diffusivity are therefore important properties governing the response of hydrate-bearing sediment to natural or man-made thermal perturbations. We seek to improve characterizations of hydrate's in situ thermal behavior by making laboratory measurements of thermal conductivity in pure sI CH4 hydrate at near in situ pressures and temperatures. Thermal conductivity measurements are made using the transient hot-wire technique of von Herzen and Maxwell, which requires that a needle probe be positioned along the axis of the cylindrical sample. Hydrate is synthesized around the probe by heating H20 "seed ice" grains in a pressurized methane atmosphere. To insure thermal contact between probe and sample, and to eliminate the porosity required by our synthesis method, samples are radially compacted after synthesis. We tested our methodology on granular ice Ih, compacted under vacuum, and its thermal conductivity is 2.16+/-0.03 W/m”K at -10° C, in agreement with published values. Our preliminary value for conductivity of pure CH4 hydrate, when compacted to less than 5% porosity, is 0.475+/-0.007 W/m”K at -5° C. Conductivity decreases slightly (0.015 W/m”K) with temperature over the range -30 to -5° C. At -30° C, thermal conductivity increases with confining pressure by 0.0125 W/m”K over the range 34.5 to 70.1 MPa. Thermal conductivity measurements above 0° C in pure CH4 hydrate are ongoing.

10. Development of a direct push based in-situ thermal conductivity measurement system

Chirla, Marian Andrei; Vienken, Thomas; Dietrich, Peter; Bumberger, Jan

2016-04-01

Heat pump systems are commonly utilized in Europe, for the exploitation of the shallow geothermal potential. To guarantee a sustainable use of the geothermal heat pump systems by saving resources and minimizing potential negative impacts induced by temperature changes within soil and groundwater, new geothermal exploration methods and tools are required. The knowledge of the underground thermal properties is a necessity for a correct and optimum design of borehole heat exchangers. The most important parameter that indicates the performance of the systems is thermal conductivity of the ground. Mapping the spatial variability of thermal conductivity, with high resolution in the shallow subsurface for geothermal purposes, requires a high degree of technical effort to procure adequate samples for thermal analysis. A collection of such samples from the soil can disturb sample structure, so great care must be taken during collection to avoid this. Factors such as transportation and sample storage can also influence measurement results. The use of technologies like Thermal Response Test (TRT) require complex mechanical and electrical systems for convective heat transport in the subsurface and longer monitoring times, often three days. Finally, by using thermal response tests, often only one integral value is obtained for the entire coupled subsurface with the borehole heat exchanger. The common thermal conductivity measurement systems (thermal analyzers) can perform vertical thermal conductivity logs only with the aid of sample procurement, or by integration into a drilling system. However, thermal conductivity measurements using direct push with this type of probes are not possible, due to physical and mechanical limitations. Applying vertical forces using direct push technology, in order to penetrate the shallow subsurface, can damage the probe and the sensors systems. The aim of this study is to develop a new, robust thermal conductivity measurement probe, for direct

11. Silver transfer in proustite Ag{sub 3}AsS{sub 3} at high temperatures: Conductivity and single-crystal X-ray studies

SciTech Connect

Gagor, Anna Pawlowski, Antoni; Pietraszko, Adam

2009-03-15

Single crystals of proustite Ag{sub 3}AsS{sub 3} have been characterised by impedance spectroscopy and single-crystal X-ray diffraction in the temperature ranges of 295-543 and 295-695 K, respectively. An analysis of the one-particle potential of silver atoms shows that in the whole measuring temperature range defects in the silver substructure play a major role in the conduction mechanism. Furthermore, the silver transfer is equally probable within silver chains and spirals, as well as between chains and spirals. The trigonal R3c room temperature phase does not change until the decomposition of the crystal. The electric anomaly of the first-order character which appears near 502 K is related to an increase in the electronic component of the total conductivity resulting from Ag{sub 2}S deposition at the sample surface. - Joint probability density function map of silver atoms at T=695 K.

12. Measurement uncertainty for the Uniform Engine Testing Program conducted at NASA Lewis Research Center

NASA Technical Reports Server (NTRS)

Abdelwahab, Mahmood; Biesiadny, Thomas J.; Silver, Dean

1987-01-01

An uncertainty analysis was conducted to determine the bias and precision errors and total uncertainty of measured turbojet engine performance parameters. The engine tests were conducted as part of the Uniform Engine Test Program which was sponsored by the Advisory Group for Aerospace Research and Development (AGARD). With the same engines, support hardware, and instrumentation, performance parameters were measured twice, once during tests conducted in test cell number 3 and again during tests conducted in test cell number 4 of the NASA Lewis Propulsion Systems Laboratory. The analysis covers 15 engine parameters, including engine inlet airflow, engine net thrust, and engine specific fuel consumption measured at high rotor speed of 8875 rpm. Measurements were taken at three flight conditions defined by the following engine inlet pressure, engine inlet total temperature, and engine ram ratio: (1) 82.7 kPa, 288 K, 1.0, (2) 82.7 kPa, 288 K, 1.3, and (3) 20.7 kPa, 288 K, 1.3. In terms of bias, precision, and uncertainty magnitudes, there were no differences between most measurements made in test cells number 3 and 4. The magnitude of the errors increased for both test cells as engine pressure level decreased. Also, the level of the bias error was two to three times larger than that of the precision error.

13. Method and apparatus for measuring thermal conductivity of small, highly insulating specimens

NASA Technical Reports Server (NTRS)

Miller, Robert A. (Inventor); Kuczmarski, Maria A. (Inventor)

2012-01-01

A hot plate method and apparatus for the measurement of thermal conductivity combines the following capabilities: 1) measurements of very small specimens; 2) measurements of specimens with thermal conductivity on the same order of that as air; and, 3) the ability to use air as a reference material. Care is taken to ensure that the heat flow through the test specimen is essentially one-dimensional. No attempt is made to use heated guards to minimize the flow of heat from the hot plate to the surroundings. Results indicate that since large correction factors must be applied to account for guard imperfections when specimen dimensions are small, simply measuring and correcting for heat from the heater disc that does not flow into the specimen is preferable. The invention is a hot plate method capable of using air as a standard reference material for the steady-state measurement of the thermal conductivity of very small test samples having thermal conductivity on the order of air.

14. Observations of Spacecraft Bearing Lubricant Redistribution Based on Thermal Conductance Measurements

NASA Technical Reports Server (NTRS)

Takeuchi, Yoshimi R.; Frantz, Peter P.; Hilton, Michael R.

2014-01-01

The performance and life of precision ball bearings are critically dependent on maintaining a quantity of oil at the ball/race interface that is sufficient to support a robust protective film. In space applications, where parched conditions are intentionally the norm, harsh operating conditions can displace the small reserves of oil, resulting in reduced film thickness and premature wear. In the past, these effects have proven difficult to model or to measure experimentally. This paper describes a study addressing this challenge, where bearing thermal conductance measurements are employed to infer changes in lubricant quantity at the critical rolling interfaces. In the first part of the paper, we explain how the lubricant's presence and its quantity impacts bearing thermal conductance measurements. For a stationary bearing, we show that conductance is directly related to the lubricant quantity in the ball/race contacts. Hence, aspects of bearing performance related to oil quantity can be understood and insights improved with thermal conductance data. For a moving bearing, a different mechanism of heat transfer dominates and is dependent on lubricant film thickness on the ball. In the second part of the report, we discuss lubricant quantity observations based on bearing thermal conductance measurements. Lubricant quantity, and thus bearing thermal conductance, depends on various initial and operating conditions and is impacted further by the run-in process. A significant effect of maximum run-in speed was also observed, with less oil remaining after obtaining higher speeds. Finally, we show that some of the lubricant that is displaced between the ball and race during run-in operation can be recovered during rest, and we measure the rate of recovery for one example.

15. A measurement technique for circumventing hysteresis and conductance drift in carbon nanotube field-effect transistors

Tunnell, Andrew; Ballarotto, Vincent; Cumings, John

2014-01-01

We present a measurement protocol that effectively eliminates both the hysteresis and the temporal drift typically observed in the channel conductance of single-walled carbon nanotube field-effect transistors (SWNT FETs) during the application of gate voltages. Before each resistance measurement, the gate is first stepped through a series of alternating positive and negative voltages to produce a neutral charge distribution within the device. This process is highly effective at removing the hysteresis in the channel conductance, and time-dependent measurements further demonstrate that the drain current is stable and single-valued, independent of the prior measurement history. The effectiveness of this method can be understood within the Preisach hysteresis model, which we demonstrate as a useful framework to predict the observed results.

16. A measurement technique for circumventing hysteresis and conductance drift in carbon nanotube field-effect transistors.

PubMed

Tunnell, Andrew; Ballarotto, Vincent; Cumings, John

2014-01-31

We present a measurement protocol that effectively eliminates both the hysteresis and the temporal drift typically observed in the channel conductance of single-walled carbon nanotube field-effect transistors (SWNT FETs) during the application of gate voltages. Before each resistance measurement, the gate is first stepped through a series of alternating positive and negative voltages to produce a neutral charge distribution within the device. This process is highly effective at removing the hysteresis in the channel conductance, and time-dependent measurements further demonstrate that the drain current is stable and single-valued, independent of the prior measurement history. The effectiveness of this method can be understood within the Preisach hysteresis model, which we demonstrate as a useful framework to predict the observed results. PMID:24394672

17. Method and Apparatus for Measuring Thermal Conductivity of Small, Highly Insulating Specimens

NASA Technical Reports Server (NTRS)

Miller, Robert A (Inventor); Kuczmarski, Maria A (Inventor)

2013-01-01

A method and apparatus for the measurement of thermal conductivity combines the following capabilities: 1) measurements of very small specimens; 2) measurements of specimens with thermal conductivity on the same order of that as air; and, 3) the ability to use air as a reference material. Care is taken to ensure that the heat flow through the test specimen is essentially one-dimensional. No attempt is made to use heated guards to minimize the flow of heat from the hot plate to the surroundings. Results indicate that since large correction factors must be applied to account for guard imperfections when specimen dimensions are small, simply measuring and correcting for heat from the heater disc that does not flow into the specimen is preferable.

18. Effect of metal complexation on the conductance of single-molecular wires measured at room temperature.

PubMed

Ponce, Julia; Arroyo, Carlos R; Tatay, Sergio; Frisenda, Riccardo; Gaviña, Pablo; Aravena, Daniel; Ruiz, Eliseo; van der Zant, Herre S J; Coronado, Eugenio

2014-06-11

The present work aims to give insight into the effect that metal coordination has on the room-temperature conductance of molecular wires. For that purpose, we have designed a family of rigid, highly conductive ligands functionalized with different terminations (acetylthiols, pyridines, and ethynyl groups), in which the conformational changes induced by metal coordination are negligible. The single-molecule conductance features of this series of molecular wires and their corresponding Cu(I) complexes have been measured in break-junction setups at room temperature. Experimental and theoretical data show that no matter the anchoring group, in all cases metal coordination leads to a shift toward lower energies of the ligand energy levels and a reduction of the HOMO-LUMO gap. However, electron-transport measurements carried out at room temperature revealed a variable metal coordination effect depending on the anchoring group: upon metal coordination, the molecular conductance of thiol and ethynyl derivatives decreased, whereas that of pyridine derivatives increased. These differences reside on the molecular levels implied in the conduction. According to quantum-mechanical calculations based on density functional theory methods, the ligand frontier orbital lying closer to the Fermi energy of the leads differs depending on the anchoring group. Thereby, the effect of metal coordination on molecular conductance observed for each anchoring could be explained in terms of the different energy alignments of the molecular orbitals within the gold Fermi level. PMID:24831452

19. On the van der Pauw's method applied to the measurement of low thermal conductivity materials.

PubMed

Morales, C; Flores, E; Bodega, J; Leardini, F; Ferrer, I J; Ares, J R; Sánchez, C

2016-08-01

The electrical van der Pauw's method has recently been extended to measure the thermal conductivity of different elements and compounds. This technique provides an easy way to determine the sample in-plane thermal conductivity by avoiding the influence of the thermal contact resistances. However, the reported calculated error values appear to be underestimated when dealing with the materials with low thermal conductivity (<5 W/Km) at room temperature. The causes of this underestimation are investigated in this communication and it has been found that they are due to the drastic influence of conduction heat losses through the thermo-resistance wires as well as the resulting modification of the sample temperature map. Both phenomena lead to experimental values of the sample thermal conductivity, which are systematically higher than the tabulated ones. The magnitude of this systematic error is ∼100% dealing with the samples of macroscopic dimensions, and low thermal conductivity indicated that the obtained accurate measurements can be quite challenging. PMID:27587145

20. Using a Divided Bar Apparatus to Measure Thermal Conductivity of Samples of Odd Sizes and Shapes

Crowell, J. "; Gosnold, W. D.

2012-12-01

Standard procedure for measuring thermal conductivity using a divided bar apparatus requires a sample that has the same surface dimensions as the heat sink/source surface in the divided bar. Heat flow is assumed to be constant throughout the column and thermal conductivity (K) is determined by measuring temperatures (T) across the sample and across standard layers and using the basic relationship Ksample=(Kstandard*(ΔT1+ΔT2)/2)/(ΔTsample). Sometimes samples are not large enough or of correct proportions to match the surface of the heat sink/source, however using the equations presented here the thermal conductivity of these samples can still be measured with a divided bar. Measurements were done on the UND Geothermal Laboratories stationary divided bar apparatus (SDB). This SDB has been designed to mimic many in-situ conditions, with a temperature range of -20C to 150C and a pressure range of 0 to 10,000 psi for samples with parallel surfaces and 0 to 3000 psi for samples with non-parallel surfaces. The heat sink/source surfaces are copper disks and have a surface area of 1,772 mm2 (2.74 in2). Layers of polycarbonate 6 mm thick with the same surface area as the copper disks are located in the heat sink and in the heat source as standards. For this study, all samples were prepared from a single piece of 4 inch limestone core. Thermal conductivities were measured for each sample as it was cut successively smaller. The above equation was adjusted to include the thicknesses (Th) of the samples and the standards and the surface areas (A) of the heat sink/source and of the sample Ksample=(Kstandard*Astandard*Thsample*(ΔT1+ΔT3))/(ΔTsample*Asample*2*Thstandard). Measuring the thermal conductivity of samples of multiple sizes, shapes, and thicknesses gave consistent values for samples with surfaces as small as 50% of the heat sink/source surface, regardless of the shape of the sample. Measuring samples with surfaces smaller than 50% of the heat sink/source surface

1. Measurement of low energy cosmic rays aboard Spacelab-1

NASA Technical Reports Server (NTRS)

Beaujean, R.; Oschlies, K.; Enge, W.

1985-01-01

In December 1983 the first Spacelab mission was launched for a duration of 10 days. Aboard was the Kiel experiment Isotopic Stack designed for measurement of heavy cosmic ray nuclei with nuclear charge equal to or greater than 3 and energies up to some 100MeV/nuc. One part of the stack was rotated in well defined steps registered by an angle encoder to receive information on impact times of the nuclei. Using this time resolving system geomagnetically forbidden particles can be detected. The chemical composition and energy spectra of mainly CNO particles are examined using a rotated 300 microns m thick CR-39 foil beneath a fixed 100 microns m thick Kodak-Cellulose Nitrate foil. About 600 sq cm have been scanned yielding nearly 100 nuclear tracks within an energy range of approximately 8 to 30 MeV/nuc. The calibration is done by means of a postflight irradiation with 410 MeV/nuc Fe-56 at Berkeley Laboratory, California, USA. Relative abundances and energy spectra are presented.

2. Development and application of diagnostic instrumentation for measurement of electron density and conductivity

SciTech Connect

Bauman, L.E.

1990-05-01

The purpose of this contract was to assemble and demonstrate in the laboratory a Faraday rotation system for measurement of electron density and conductivity, with the intent to produce a system suitable for diagnostic support of the development of pulsed, space-based magnetohydrodynamic (MHD) power systems. Two system configurations were tested: (1) a rotating polarizer and (2) a beam splitting polarizer. Due to the short path length plasma produced in the laboratory flame, the long wavelength 496 {mu}m methyl fluoride laser line was used and only the more sensitive rotating polarizer configuration was used for the demonstration experiments. Electron number densities from 2 {times} 10{sup 19} to 9 {times} 10{sup 19} were measured with good agreement to statistical equilibrium (Saha) calculations using emission absorption-measured flame temperatures and neutral seed atom number seed atom nuclear densities. The electron collision frequencies were measured by transmission measurements. Combining these two measurements gave measured electron conductivities of between 4 and 12 mohs/m. These results compared reasonably well with those found with an electron collision frequency model combined with chemical equilibrium calculations and the emission absorption measurements. Ellipticity measurements of electron collision frequency were not possible due to the short path length of the laboratory plasma. 46 refs., 25 figs., 9 tabs.

3. Measurement of Apparent Thermal Conductivity of JSC-1A Under Ambient Pressure

NASA Technical Reports Server (NTRS)

Yuan, Zeng-Guang; Kleinhenz, Julie E.

2011-01-01

The apparent thermal conductivity of JSC-1A lunar regolith simulant was measured experimentally using a cylindrical apparatus. Eleven thermocouples were embedded in the simulant bed to obtain the steady state temperature distribution at various radial, axial, and azimuthal locations. The high aspect ratio of a cylindrical geometry was proven to provide a one-dimensional, axisymmetric temperature field. A test series was performed at atmospheric pressure with varying heat fluxes. The radial temperature distribution in each test fit a logarithmic function, indicating a constant thermal conductivity throughout the soil bed. However, thermal conductivity was not constant between tests at different heat fluxes. This variation is attributed to stresses created by thermal expansion of the simulant particles against the rigid chamber wall. Under stress-free conditions (20 deg C), the data suggest a temperature independent apparent conductivity of 0.1961 +/- 0.0070 W/m/ deg C

4. A steady-state high-temperature method for measuring thermal conductivity of refractory materials

Manzolaro, M.; Corradetti, S.; Andrighetto, A.; Ferrari, L.

2013-05-01

A new methodology and an instrumental setup for the thermal conductivity estimation of isotropic bulk graphite and different carbides at high temperatures are presented. The method proposed in this work is based on the direct measurement of temperature and emissivity on the top surface of a sample disc of known dimensions. Temperatures measured under steady-state thermal equilibrium are then used to estimate the thermal conductivity of the sample by making use of the inverse parameter estimation technique. Thermal conductivity values obtained in this way are then compared to the material data sheets and values found in literature. The reported work has been developed within the Research and Development framework of the SPES (Selective Production of Exotic Species) project at INFN-LNL (Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali di Legnaro).

5. Measurements of middle-atmosphere electric fields and associated electrical conductivities

NASA Technical Reports Server (NTRS)

Hale, L. C.; Croskey, C. L.; Mitchell, J. D.

1981-01-01

A simple antenna for measuring the vertical electric field in the 'middle atmosphere' has been flown on a number of rocket-launched parachute-borne payloads. The data from the first nine such flights, launched under a variety of geophysical conditions, are presented, along with electrical conductivities measured simultaneously. The data include indications of layered peaks of several volts per meter in the mesospheric field at high and low latitudes in situations of relatively low conductivity. During an auroral 'REP' event the electric field reversed direction in the lower stratosphere, accompanied by a substantial enhancement in conductivity. The data generally do not confirm speculations based only on the extension of the thunderstorm circuit from below or the mapping of ionospheric and magnetospheric fields from above, but seem to require, in addition, internal generation processes in the middle atmosphere.

6. Thermal conductivity of donor-doped GaN measured with 3ω and stationary methods

Churiukova, O.; JeŻowski, A.; Stachowiak, P.; Mucha, J.; Litwicki, Z.; Perlin, P.; Suski, T.

2015-07-01

The thermal conductivity of three single crystal samples of n-type gallium nitride with electron densities of 4.0 × 1016, 2.6 × 1018, and 1.1 × 1020 cm-3 has been determined in the temperature range 4-320 K. The measurements were carried out within the ab plane using the stationary method. The thermal conductivity depends strongly on the donor concentration. The analysis within the Callaway approach and the Debye model shows a significant influence of phonon-electron scattering on the thermal conductivity of the samples. In addition, some preliminary results obtained along the c axes of GaN layered samples are presented. The latter measurements have been carried out using the 3ω method.

7. A steady-state high-temperature method for measuring thermal conductivity of refractory materials.

PubMed

Manzolaro, M; Corradetti, S; Andrighetto, A; Ferrari, L

2013-05-01

A new methodology and an instrumental setup for the thermal conductivity estimation of isotropic bulk graphite and different carbides at high temperatures are presented. The method proposed in this work is based on the direct measurement of temperature and emissivity on the top surface of a sample disc of known dimensions. Temperatures measured under steady-state thermal equilibrium are then used to estimate the thermal conductivity of the sample by making use of the inverse parameter estimation technique. Thermal conductivity values obtained in this way are then compared to the material data sheets and values found in literature. The reported work has been developed within the Research and Development framework of the SPES (Selective Production of Exotic Species) project at INFN-LNL (Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali di Legnaro). PMID:23742578

8. Analysis of Thermal-Conductivity Measurement Data from International Comparison of National Laboratories

Hay, B.; Zarr, R.; Stacey, C.; Lira-Cortes, L.; Hammerschmidt, U.; Sokolov, N.; Zhang, J.; Filtz, J.-R.; Fleurence, N.

2013-05-01

For the first time under the auspices of the Bureau International des Poids et Mesures (BIPM), seven national metrology institutes (NMIs) participated in an international interlaboratory comparison on thermal-conductivity measurements by the guarded hot-plate method. Measurements were conducted successively by all participants on the same set of specimens of insulating materials (mineral wool and expanded polystyrene) at temperatures ranging from 10 °C to 40 °C, according to the International Standard ISO 8302. This protocol aims to minimize issues of material variability by circulating the same pairs of specimens among the laboratories following the strict format of a round-robin test program. This comparison is a pilot study which is intended as a first stage for future key comparisons between NMIs. The descriptive analysis of obtained results shows good agreement between laboratories for the mineral wool (MW) specimens and the thicker specimens of expanded polystyrene (EPS), with relative deviations within the uncertainties of measurement. A positive drift of thermal-conductivity values, which has appeared progressively during the comparison process, seems to be correlated with the size of the metering area of the guarded hot plates used. A statistical analysis was applied to repeated thermal-conductivity measurements at 23 °C, to identify anomalous and outlying data, to assess the within- and between-laboratory variability, and to evaluate the participant laboratories' performance.

9. Optical approach to thermopower and conductivity measurements in thin-film semiconductors

SciTech Connect

Dersch, H.; Amer, N.M.

1984-08-01

An optical beam deflection technique is applied to measure the Joule and Peltier heat generated by electric currents through thin-film semiconductors. The method yields a spatially resolved conductivity profile and allows the determination of Peltier coefficients. Results obtained on doped hydrogenated amorphous silicon films are presented.

10. Using Conductivity Measurements to Determine the Identities and Concentrations of Unknown Acids: An Inquiry Laboratory Experiment

ERIC Educational Resources Information Center

Smith, K. Christopher; Garza, Ariana

2015-01-01

This paper describes a student designed experiment using titrations involving conductivity measurements to identify unknown acids as being either HCl or H[subscript 2]SO[subscript 4], and to determine the concentrations of the acids, thereby improving the utility of standard acid-base titrations. Using an inquiry context, students gain experience…

11. A Hot-Wire Method Based Thermal Conductivity Measurement Apparatus for Teaching Purposes

ERIC Educational Resources Information Center

Alvarado, S.; Marin, E.; Juarez, A. G.; Calderon, A.; Ivanov, R.

2012-01-01

The implementation of an automated system based on the hot-wire technique is described for the measurement of the thermal conductivity of liquids using equipment easily available in modern physics laboratories at high schools and universities (basically a precision current source and a voltage meter, a data acquisition card, a personal computer…

12. A study of rock matrix diffusion properties by electrical conductivity measurements

SciTech Connect

Ohlsson, Y.; Neretnieks, I.

1999-07-01

Traditional rock matrix diffusion experiments on crystalline rock are very time consuming due to the low porosity and extensive analysis requirements. Electrical conductivity measurements are, on the other hand, very fast and larger samples can be used than are practical in ordinary diffusion experiments. The effective diffusivity of a non-charged molecule is readily evaluated from the measurements, and influences from surface conductivity on diffusion of cations can be studied. A large number of samples of varying thickness can be measured within a short period, and the changes in transport properties with position in a rock core can be examined. In this study the formation factor of a large number of Aespoe diorite samples is determined by electrical conductivity measurements. The formation factor is a geometric factor defined as the ratio between the effective diffusivity of a non-charged molecule, to that of the same molecule in free liquid. The variation of this factor with position among a borecore and with sample length, and its coupling to the porosity of the sample is studied. Also the surface conductivity is studied. This was determined as the residual conductivity after leaching of the pore solution ions. The formation factor of most of the samples is in the range 1E-5 to 1E-4, with a mean value of about 5E-5. Even large samples (4--13 cm) give such values. The formation factor increases with increasing porosity and the change in both formation factor and porosity with position in the borecore can be large, even for samples close to each other. The surface conductivity increases with increasing formation factor for the various samples but the influence on the pore diffusion seems to be higher for samples of lower formation factor. This suggests that the relation between the pore surface area and the pore volume is larger for samples of low formation factor.

13. X-ray scattering measurements of dissociation-induced metallization of dynamically compressed deuterium

PubMed Central

Davis, P.; Döppner, T.; Rygg, J. R.; Fortmann, C.; Divol, L.; Pak, A.; Fletcher, L.; Becker, A.; Holst, B.; Sperling, P.; Redmer, R.; Desjarlais, M. P.; Celliers, P.; Collins, G. W.; Landen, O. L.; Falcone, R. W.; Glenzer, S. H.

2016-01-01

Hydrogen, the simplest element in the universe, has a surprisingly complex phase diagram. Because of applications to planetary science, inertial confinement fusion and fundamental physics, its high-pressure properties have been the subject of intense study over the past two decades. While sophisticated static experiments have probed hydrogen's structure at ever higher pressures, studies examining the higher-temperature regime using dynamic compression have mostly been limited to optical measurement techniques. Here we present spectrally resolved x-ray scattering measurements from plasmons in dynamically compressed deuterium. Combined with Compton scattering, and velocity interferometry to determine shock pressure and mass density, this allows us to extract ionization state as a function of compression. The onset of ionization occurs close in pressure to where density functional theory-molecular dynamics (DFT-MD) simulations show molecular dissociation, suggesting hydrogen transitions from a molecular and insulating fluid to a conducting state without passing through an intermediate atomic phase. PMID:27079420

14. Relating x-ray attenuation measurements to water content and distribution in SB-15D core

SciTech Connect

Bonner, B.P.; Roberts, J.J.; Schneberk, D.J

1996-09-30

Making improved estimates of the water content of The Geysers reservoir is fundamental to efficient and economic long term production of steam power from the resource. A series of coordinated physical properties measurements form core recovered from the SB-15D, reported in this volume in a series of papers, have been made to better understand water storage and to relate water content and distribution to observable geophysical properties such as electrical conductivity and seismic velocities. A principal objective here is to report new interpretations of x-ray scans made within 72 hours of core recovery from SB-15D, which suggest, taking advantage of preliminary measurements of capillary suction for metagraywacke, that water content was low in much of the preserved core.

15. X-ray scattering measurements of dissociation-induced metallization of dynamically compressed deuterium.

PubMed

Davis, P; Döppner, T; Rygg, J R; Fortmann, C; Divol, L; Pak, A; Fletcher, L; Becker, A; Holst, B; Sperling, P; Redmer, R; Desjarlais, M P; Celliers, P; Collins, G W; Landen, O L; Falcone, R W; Glenzer, S H

2016-01-01

Hydrogen, the simplest element in the universe, has a surprisingly complex phase diagram. Because of applications to planetary science, inertial confinement fusion and fundamental physics, its high-pressure properties have been the subject of intense study over the past two decades. While sophisticated static experiments have probed hydrogen's structure at ever higher pressures, studies examining the higher-temperature regime using dynamic compression have mostly been limited to optical measurement techniques. Here we present spectrally resolved x-ray scattering measurements from plasmons in dynamically compressed deuterium. Combined with Compton scattering, and velocity interferometry to determine shock pressure and mass density, this allows us to extract ionization state as a function of compression. The onset of ionization occurs close in pressure to where density functional theory-molecular dynamics (DFT-MD) simulations show molecular dissociation, suggesting hydrogen transitions from a molecular and insulating fluid to a conducting state without passing through an intermediate atomic phase. PMID:27079420

16. X-ray scattering measurements of dissociation-induced metallization of dynamically compressed deuterium

Davis, P.; Döppner, T.; Rygg, J. R.; Fortmann, C.; Divol, L.; Pak, A.; Fletcher, L.; Becker, A.; Holst, B.; Sperling, P.; Redmer, R.; Desjarlais, M. P.; Celliers, P.; Collins, G. W.; Landen, O. L.; Falcone, R. W.; Glenzer, S. H.

2016-04-01

Hydrogen, the simplest element in the universe, has a surprisingly complex phase diagram. Because of applications to planetary science, inertial confinement fusion and fundamental physics, its high-pressure properties have been the subject of intense study over the past two decades. While sophisticated static experiments have probed hydrogen's structure at ever higher pressures, studies examining the higher-temperature regime using dynamic compression have mostly been limited to optical measurement techniques. Here we present spectrally resolved x-ray scattering measurements from plasmons in dynamically compressed deuterium. Combined with Compton scattering, and velocity interferometry to determine shock pressure and mass density, this allows us to extract ionization state as a function of compression. The onset of ionization occurs close in pressure to where density functional theory-molecular dynamics (DFT-MD) simulations show molecular dissociation, suggesting hydrogen transitions from a molecular and insulating fluid to a conducting state without passing through an intermediate atomic phase.

17. Residual stress measurements on thick plate low-alloy steel narrow gap weldments by x-ray diffraction

SciTech Connect

Rund, C.O.; DiMascio, P.S.; Pangborn, R.N.; Snoha, D.J.

1984-06-01

A unique x-ray diffraction instrument for residual stress measurement has been developed that provides for speed, ease of measurement, accuracy, and economy of surface stress measurement. Application of this instrument with a material removal technique, e.g., electropolishing, has facilitated detailed, high resolution studies of three-dimensional stress fields. This paper describes the instrumentation and techniques applied to conduct the residual stress measurement and presents maps of the residual stress data obtained for the surfaces of a heavy 2 1/4 Cr 1 Mo steel plate weldment.

18. Thermal-conductivity measurements of tungsten-fiber-reinforced superalloy composites using a thermal-conductivity comparator

NASA Technical Reports Server (NTRS)

Westfall, L. J.; Winsa, E. A.

1979-01-01

The thermal conductivity (TC) of tungsten-fiber-reinforced superalloys was determined for two composite systems by using a thermal conductivity standard from the National Bureau of Standards and a comparator and technique developed for that purpose. The results were compared with TC data for the nickel-base alloy MAR-M200. The technique lends itself to applications involving thin specimens, such as thin-walled turbine blades. The TC's of the composite systems were considerably higher in both the longitudinal and transverse directions than that of the monolithic superalloys used as the matrices.

19. Temporal changes of hydraulic conductivity of cultivated soil studied with help of multipoint tension infiltrometer and X-ray computed tomography

Klipa, Vladimir; Zumr, David; Snehota, Michal; Dohnal, Michal

2016-04-01

Soil aggregates, its shape, size and spatial distribution affect the pores arrangement and thus govern the hydraulic conductivity of soil and soil moisture regime. On arable lands the soil is exposed to rapid structural changes within each growing season due to agrotechnical practices, quick crop and root growth, soil biota and climatic conditions. This contribution is mainly focused on temporal changes of unsaturated hydraulic conductivity of cultivated soil. The research is supplemented by detailed analysis of CT images of soil samples for better understanding of structural change of soil during the year and its impact on soil hydraulic conductivity. The infiltration experiments were done using automated multipoint tension infiltrometer recently developed at CTU in Prague on the plots located on the Nucice experimental catchment. The catchment is situated in a moderately hilly area in central Bohemia (Czech Republic). Fourteen regular infiltration campaigns (77 individual infiltration experiments) were conducted from October 2012 until July 2015 on a single arable plot. In general, agricultural practice captured involved complete life cycle from sowing, through harvest, to postharvest stubble breaking. Weather conditions during infiltration experiments ranged from clear-sky to light rain, with temperatures between 8 and 30°C. All measurements were consistently performed with small suction of 3 cm and hydraulic conductivities were determined using extended semiempirical estimation procedure of Zhang. Results show that unsaturated hydraulic conductivity was the lowest in early spring and did increase at beginning of summer in the years 2012 - 2014. During the summer and autumn (2012 - 2014) the unsaturated hydraulic conductivity remained relatively unchanged. On the contrary, results in the year 2015 show opposite trend - the highest hydraulic conductivity was observed in early spring and did gradually decrease until the end of July. In both cases, however, the

20. Photoacoustic infrared spectroscopy for conducting gas tracer tests and measuring water saturations in landfills.

PubMed

Jung, Yoojin; Han, Byunghyun; Mostafid, M Erfan; Chiu, Pei; Yazdani, Ramin; Imhoff, Paul T

2012-02-01

Gas tracer tests can be used to determine gas flow patterns within landfills, quantify volatile contaminant residence time, and measure water within refuse. While gas chromatography (GC) has been traditionally used to analyze gas tracers in refuse, photoacoustic spectroscopy (PAS) might allow real-time measurements with reduced personnel costs and greater mobility and ease of use. Laboratory and field experiments were conducted to evaluate the efficacy of PAS for conducting gas tracer tests in landfills. Two tracer gases, difluoromethane (DFM) and sulfur hexafluoride (SF(6)), were measured with a commercial PAS instrument. Relative measurement errors were invariant with tracer concentration but influenced by background gas: errors were 1-3% in landfill gas but 4-5% in air. Two partitioning gas tracer tests were conducted in an aerobic landfill, and limits of detection (LODs) were 3-4 times larger for DFM with PAS versus GC due to temporal changes in background signals. While higher LODs can be compensated by injecting larger tracer mass, changes in background signals increased the uncertainty in measured water saturations by up to 25% over comparable GC methods. PAS has distinct advantages over GC with respect to personnel costs and ease of use, although for field applications GC analyses of select samples are recommended to quantify instrument interferences. PMID:21996285

1. Thermal conductance measurements of bolted copper to copper joints at sub-Kelvin temperatures

Didschuns, I.; Woodcraft, A. L.; Bintley, D.; Hargrave, P. C.

2004-05-01

We have measured the thermal contact conductance of several demountable copper joints below 1 K. Joints were made by bolting together either two flat surfaces or a clamp around a rod. Surfaces were gold plated, and no intermediate materials were used. A linear dependence on temperature was seen. Most of the measured conductance values fell into a narrow range: 0.1-0.2 W K -1 at 1 K. Results in the literature for similar joints consist of predictions based on electrical resistance measurements using the Wiedemann-Franz law. There is little evidence of the validity of this law in the case of joints. Nevertheless, our results are in good agreement with the literature predictions, suggesting that such predictions are a reasonable approximation.

2. Simultaneous reconstruction of permittivity and conductivity using multi-frequency admittance measurement in electrical capacitance tomography

Zhang, Maomao; Soleimani, Manuchehr

2016-02-01

Electrical capacitance tomography (ECT) is an imaging method mainly capable of reconstructing dielectric permittivity. Generally, the reactance part of complex admittance is measured in a selected frequency. This paper presents for the first time an in depth and systematic analysis of complex admittance data for simultaneous reconstruction of both electrical conductivity and dielectric permittivity. A complex-valued forward model, Jacobian matrix and inverse solution are developed in the time harmonic excitation mode to allow for multi-frequency measurements. Realistic noise models are used to evaluate the performance of complex admittance ECT in a range of excitation frequencies. This paper demonstrates far greater potential for ECT as a versatile imaging tool through novel analysis of complex admittance imaging using a dual conductivity permittivity inversion method. The paper demonstrates that various classes of contactless capacitance based measurement devices can be analysed through complex multi-frequency ECT.

3. A robust and well shielded thermal conductivity device for low temperature measurements.

PubMed

Toews, W H; Hill, R W

2014-04-01

We present a compact mechanically robust thermal conductivity measurement apparatus for measurements at low temperatures (<1 K) and high magnetic fields on small high-purity single crystal samples. A high-conductivity copper box is used to enclose the sample and all the components. The box provides protection for the thermometers, heater, and most importantly the sample increasing the portability of the mount. In addition to physical protection, the copper box is also effective at shielding radio frequency electromagnetic interference and thermal radiation, which is essential for low temperature measurements. A printed circuit board in conjunction with a braided ribbon cable is used to organize the delicate wiring and provide mechanical robustness. PMID:24784624

4. Heat treatment effect on the electronic and magnetic structures of nanographene sheets investigated through electron spectroscopy and conductance measurements.

PubMed

Takashiro, Jun-ichi; Kudo, Yasuhiko; Kaneko, Satoshi; Takai, Kazuyuki; Ishii, Takafumi; Kyotani, Takashi; Enoki, Toshiaki; Kiguchi, Manabu

2014-04-28

The heat treatment effect on the electronic and magnetic structures of a disordered network of nanographene sheets has been investigated by in situ measurements of X-ray photoemission spectroscopy, near-edge X-ray absorption fine structure (NEXAFS), and electrical conductance, together with temperature-programmed desorption measurements. Oxygen-containing functional groups bonded to nanographene edges in the pristine sample are almost completely decomposed under heat treatment up to 1300-1500 K, resulting in the formation of edges primarily terminated by hydrogen. The removal of the oxygen-containing groups enhances the conductance owing to the decrease in the electron transport barriers between nanographene sheets. Heat treatment above 1500 K removes also the hydrogen atoms from the edges, promoting the successive fusion of nanographene sheets at the expense of edges. The decrease in the π* peak width in NEXAFS indicates the progress of the fusion reaction, that is, the extension of the π-conjugation, which agrees with the increase in the orbital susceptibility previously reported. The fusion leads to the formation of local π/sp(2) bridges between nanographene sheets and brings about an insulator-to-metal transition at 1500-1600 K, at which the bridge network becomes infinite. As for the magnetism, the intensity of the edge state peak in NEXAFS, which corresponds to the number of the spin-polarized edge states, decreases above 1500 K, though the effective edge-state spin density per edge state starts decreasing at approximately 200 K lower than the temperature of the edge state peak change. This disagreement indicates the development of antiferromagnetic short range ordering as a precursor of a spin glass state near the insulator-metal transition, at which the random network of inter-nanographene-sheet exchange interactions strengthened with the formation of the π/sp(2) bridges becomes infinite. PMID:24618730

5. Satellite measurements of the isotopic composition of galactic cosmic rays

NASA Technical Reports Server (NTRS)

Mewaldt, R. A.; Spalding, J. D.; Stone, E. C.; Vogt, R. E.

1979-01-01

The individual isotopes of galactic cosmic ray Ne, Mg, and Si at 100 MeV/nucleon were clearly resolved with an rms mass resolution of 0.20 amu. The results suggest the cosmic ray source is enriched in Ne-22, Mg-25, and Mg-26 when compared to the solar system. The ratio of (Mg-25)+(Mg-26) to Mg-24, which is approximately 0.49 compared to the solar system value of 0.27, suggest that the cosmic ray source and solar system material were synthesized under different conditions.

6. Pump-probe measurements of the thermal conductivity tensor for materials lacking in-plane symmetry

Feser, Joseph P.; Liu, Jun; Cahill, David G.

2014-10-01

We previously demonstrated an extension of time-domain thermoreflectance (TDTR) which utilizes offset pump and probe laser locations to measure in-plane thermal transport properties of multilayers. However, the technique was limited to systems of transversely isotropic materials studied using axisymmetric laser intensities. Here, we extend the mathematics so that data reduction can be performed on non-transversely isotropic systems. An analytic solution of the diffusion equation for an N-layer system is given, where each layer has a homogenous but otherwise arbitrary thermal conductivity tensor and the illuminating spots have arbitrary intensity profiles. As a demonstration, we use both TDTR and time-resolved magneto-optic Kerr effect measurements to obtain thermal conductivity tensor elements of <110> α-SiO2. We show that the out-of-phase beam offset sweep has full-width half-maxima that contains nearly independent sensitivity to the in-plane thermal conductivity corresponding to the scanning direction. Also, we demonstrate a Nb-V alloy as a low thermal conductivity TDTR transducer layer that helps improve the accuracy of in-plane measurements.

7. Pump-probe measurements of the thermal conductivity tensor for materials lacking in-plane symmetry

SciTech Connect

Feser, Joseph P.; Liu, Jun; Cahill, David G.

2014-10-15

We previously demonstrated an extension of time-domain thermoreflectance (TDTR) which utilizes offset pump and probe laser locations to measure in-plane thermal transport properties of multilayers. However, the technique was limited to systems of transversely isotropic materials studied using axisymmetric laser intensities. Here, we extend the mathematics so that data reduction can be performed on non-transversely isotropic systems. An analytic solution of the diffusion equation for an N-layer system is given, where each layer has a homogenous but otherwise arbitrary thermal conductivity tensor and the illuminating spots have arbitrary intensity profiles. As a demonstration, we use both TDTR and time-resolved magneto-optic Kerr effect measurements to obtain thermal conductivity tensor elements of <110> α-SiO{sub 2}. We show that the out-of-phase beam offset sweep has full-width half-maxima that contains nearly independent sensitivity to the in-plane thermal conductivity corresponding to the scanning direction. Also, we demonstrate a Nb-V alloy as a low thermal conductivity TDTR transducer layer that helps improve the accuracy of in-plane measurements.

8. Time- and Space-Domain Measurements of the Thermal Conductivity in Diamond Anvil Cells

Goncharov, A. F.

2011-12-01

I will give an overview of recent developments of experimental techniques to measure the thermal conductivity in diamond anvil cell (DAC) under conditions of high pressure and high temperature (P-T) which are relevant for the planetary interiors. To measure the lattice contributions to the thermal conductivity, we developed a transient heating technique (THT) in the diamond anvil cell (DAC) [1]. This technique utilizes a periodic front surface temperature variation (measured by the spectroradiometry) of a metallic absorber surrounded by the material of interest and exposed to a pulsed laser radiation (10 nanoseconds pulses). We extract the thermal diffusivity of minerals by fitting the experimental results to the model finite element (FE) calculations. We have recently modified this technique for microseconds laser pulses as this allows avoiding nonequilibrium heat transfer processes. We have measured the thermal conductivity of Ar up to 50 GPa and 2500 K; the results are in agreement with the theoretical calculations [2] in the limit of high temperatures. In collaboration with a group from the University of Illinois we have utilized a time-domain thermoreflectance (TDTR)- ultrafast (femtosecond) laser pump-probe technique for measurement of the lattice thermal conductivity at high P-T conditions. We have measured the thermal conductivity of MgO up to 60 GPa and 300 K and up to 45 GPa at 600 K. The detailed results of this study will be presented in a separate paper at this Meeting. Finally, we have combined static and pulsed laser techniques to determine the thermal conductivity of Fe and its temperature dependence at high pressures up to 70 GPa and 2000 K [3]. A thin plate of Fe was positioned in an Ar medium, laser heated from one side and the temperature is being measured from both sides of the sample radiometrically. The thermal conductivity has been determined by fitting the results of FE calculations to the experimental results. These examples demonstrate

9. Spatial relationship between the productivity of cane sugar and soil electrical conductivity measured by electromagnetic induction

Siqueira, Glecio; Silva, Jucicléia; Bezerra, Joel; Silva, Enio; Montenegro, Abelardo

2013-04-01

The cultivation of sugar cane in Brazil occupies a prominent place in national production chain, because the country is the main world producer of sugar and ethanol. Accordingly, studies are needed that allow an integrated production and technified, and especially that estimates of crops are consistent with the actual production of each region. The objective of this study was to determine the spatial relationship between the productivity of cane sugar and soil electrical conductivity measured by electromagnetic induction. The field experiment was conducted at an agricultural research site located in Goiana municipality, Pernambuco State, north-east of Brazil (Latitude 07 ° 34 '25 "S, Longitude 34 ° 55' 39" W). The surface of the studied field is 6.5 ha, and its mean height 8.5 m a.s.l. This site has been under sugarcane (Saccharum officinarum sp.) monoculture during the last 24 years and it was managed burning the straw each year after harvesting, renewal of plantation was performed every 7 years. Studied the field is located 10 km east from Atlantic Ocean and it is representative of the regional landscape lowlands, whose soils are affected by salinity seawater, sugarcane plantations with the main economical activity. Soil was classified an orthic the Podsol. The productivity of cane sugar and electrical conductivity were measured in 90 sampling points. The productivity of cane sugar was determined in each of the sampling points in plots of 9 m2. The Apparent soil electrical conductivity (ECa, mS m-1) was measured with an electromagnetic induction device EM38-DD (Geonics Limited). The equipment consists of two units of measurement, one in a horizontal dipole (ECa-H) to provide effective measurement distance of 1.5 m approximately and other one in vertical dipole (ECa-V) with an effective measurement depth of approximately 0.75 m. Data were analyzed using descriptive statistics and geostatistical tools. The results showed that productivity in the study area

10. Spectroscopic Laboratory Astrophysics Experiments Conducted at the LLNL EBIT Facility in Support of NASA's X-ray Astronomy Flight Program

Brown, Gregory V.; Adams, J. S.; Beiersdorfer, P.; Chen, H.; Clementson, J.; Frankel, M.; Graf, A.; Gu, M. F.; Kahn, S. M.; Kelley, R.; Kilbourne, C. A.; Koutroumpa, D.; Leutenegger, M.; Porter, F.; Wargelin, B.

2009-12-01

The electron beam ion trap (EBIT) facility located at the Lawrence Livermore National Laboratory has been used for laboratory astrophysics experiments for over 15 years. During this time, several unique spectrometers and operating modes have been developed and implemented, including high resolution grating and crystal spectrometers, a high-resolution, high-efficiency NASA/GSFC microcalorimeter array, and the ability to operate and record datawith the electron beam turned off, i.e., in the so-called magnetic trapping mode. Targeted experiments conducted at this facility have addressed specific problems faced by the X-ray astrophysics community and have provided accurate, complete sets of atomic data such as relative and absolute excitation cross sections, transition wavelengths, line polarization, and X-ray signatures of charge exchange recombination. Here we will present a brief overview of our facility and some of the more recent results including 1/4 keV band X- ray emission produced by charge exchange between L-shell sulfur ions and neutral gas, wavelengths and relative intensities of satellite X- ray lines from Na-like Fe XVI and their contribution to the Fe XVII line emission, and the relative intensities of the 3s-2p/3d-2p lines in F-like Fe XVIII and Ni XX. Part of this work was performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and is also supported by NASA grants to LLNL, GSFC, and Stanford University.

11. Flow velocimetry for weakly conducting electrolytes based on high resolution Lorentz force measurement.

Resagk, Christian; Ebert, Reschad; Vasilyan, Suren; Wiederhold, Andreas

2013-11-01

We demonstrate that a flow velocity measurement can be transformed into a non-invasive force measurement by metering the drag force acting on a system of magnets around a flow channel. This method is called Lorentz force velocimetry and has been developed in the last years in our institute. It is a feasible principle for materials with large conductivity like liquid metals. To evolve this method for weakly conducting fluids like salt water or molten glass the drag force measurement is the challenging bottleneck. Here forces of 10-8 and less of the weight force of the magnet system have to be resolved. In this paper different force measurement techniques get tested and compared. For the current setup the magnet system is attached to a state of the art electromagnetic force compensation balance. Different ways of getting the correct force signal out of the two measurement setups will be presented and discussed. For generalization of the measurement principle the Lorentz force is determined for different fluid profiles. In addition to that we have developed new systematic noise reduction methods to increase the resolution of the force measurement techniques by a factor of ten or larger which we will present here.

12. Estimation of in-situ thermal conductivities from temperature gradient measurements

SciTech Connect

Hoang, V.T.

1980-12-01

A mathematical model has been developed to study the effect of variable thermal conductivity of the formations, and the wellbore characteristics, on the fluid temperature behavior inside the wellbore during injection or production and after shut-in. During the injection or production period the wellbore fluid temperature is controlled mainly by the fluid flow rate and the heat lost from the fluid to the formation. During the shut-in period, the fluid temperature is strongly affected by differences in the formation thermal conductivities. Based on the results of the present analysis, two methods for estimating in-situ thermal conductivity were derived. First, the line source concept is extended to estimate values of the formation thermal conductivities utilizing the fluid temperature record during the transient period of injection or production and shut-in. The second method is applied when a well is under thermal equilibrium conditions. Values of the formation thermal conductivities can also be estimated by using a continuous temperature gradient log and by measuring the thermal conductivity of the formation at a few selected wellbore locations.

13. Thermal Conductivity Measurements of Aggregated (Bi1- x Sb x )2Te3 Nanoparticles Using 3 ω Method

Nishino, Shunsuke; Koyano, Mikio; Ohdaira, Keisuke

2015-06-01

Using the 3 ω method based on the two heat flow model, the thermal conductivity of as-dried and thermally treated samples of (Bi1- x Sb x )2Te3 inks in the form of aggregated nanoparticles was measured. For the as-dried sample, κ sample was 0.2 W K-1 m-1 to 0.3 W K-1 m-1. That of the thermally treated sample was 0.4 W K-1 m-1 to 0.7 W K-1 m-1. Organic solvent remained in the as-dried sample, covering the (Bi1- x Sb x )2Te3 nanoparticles. In the region where organic solvent remained between the nanoparticles, heat flow was impeded because the thermal conductivity of the organic solvent is lower than that of the (Bi1- x Sb x )2Te3 nanoparticles. However, in the thermally treated sample, the organic solvent evaporated and the nanoparticles grew due to the effects of the thermal treatment process. In this case, factors impeding heat flow, such as the interfacial thermal resistance between the particles, were limited. Therefore, this difference in κ sample, which is consistent with the grain growth as ascertained from powder x-ray diffraction measurements, can be attributed to the evaporation of the organic solvent.

14. High temperature thermal conductivity measurements of UO/sub 2/ by Direct Electrical Heating. Final report. [MANTRA-III

SciTech Connect

Bassett, B

1980-10-01

High temperature properties of reactor type UO/sub 2/ pellets were measured using a Direct Electrical Heating (DEH) Facility. Modifications to the experimental apparatus have been made so that successful and reproducible DEH runs may be carried out while protecting the pellets from oxidation at high temperature. X-ray diffraction measurements on the UO/sub 2/ pellets have been made before and after runs to assure that sample oxidation has not occurred. A computer code has been developed that will model the experiment using equations that describe physical properties of the material. This code allows these equations to be checked by comparing the model results to collected data. The thermal conductivity equation for UO/sub 2/ proposed by Weilbacher has been used for this analysis. By adjusting the empirical parameters in Weilbacher's equation, experimental data can be matched by the code. From the several runs analyzed, the resulting thermal conductivity equation is lambda = 1/4.79 + 0.0247T/ + 1.06 x 10/sup -3/ exp(-1.62/kT/) - 4410. exp(-3.71/kT/) where lambda is in w/cm K, k is the Boltzman constant, and T is the temperature in Kelvin.

15. Measurement of the optical properties of a transparent, conductive carbon nanotube film using spectroscopic ellipsometry

Kuwahara, Masashi; Kim, Yeji; Azumi, Reiko

2015-07-01

We have measured the complex refractive indices of a transparent, conductive carbon nanotube film by spectroscopic ellipsometry at wavelengths of 300-1700 nm (this includes the visible range). The film was produced on a quartz substrate by the doctor-blade method using single-walled carbon nanotube-polymer ink. The imaginary part of the complex refractive index of the film was found to be lower than 0.09 over the entire wavelength range. This film has a large advantage as a transparent, flexible, and conductive material.

16. A hot-wire method based thermal conductivity measurement apparatus for teaching purposes

Alvarado, S.; Marín, E.; Juárez, A. G.; Calderón, A.; Ivanov, R.

2012-07-01

The implementation of an automated system based on the hot-wire technique is described for the measurement of the thermal conductivity of liquids using equipment easily available in modern physics laboratories at high schools and universities (basically a precision current source and a voltage meter, a data acquisition card, a personal computer and a high purity platinum wire). The wire, which is immersed in the investigated sample, is heated by passing a constant electrical current through it, and its temperature evolution, ΔT, is measured as a function of time, t, for several values of the current. A straightforward methodology is then used for data processing in order to obtain the liquid thermal conductivity. The start point is the well known linear relationship between ΔT and ln(t) predicted for long heating times by a model based on a solution of the heat conduction equation for an infinite lineal heat source embedded in an infinite medium into which heat is conducted without convective and radiative heat losses. A criterion is used to verify that the selected linear region is the one that matches the conditions imposed by the theoretical model. As a consequence the method involves least-squares fits in linear, semi-logarithmic (semi-log) and log-log graphs, so that it becomes attractive not only to teach about heat transfer and thermal properties measurement techniques, but also as a good exercise for students of undergraduate courses of physics and engineering learning about these kinds of mathematical functional relationships between variables. The functionality of the experiment was demonstrated by measuring the thermal conductivity in samples of liquids with well known thermal properties.

17. Picosecond x-ray measurements from 100 eV to 30 keV

SciTech Connect

Attwood, D.T.; Kauffman, R.L.; Stradling, G.L.

1980-10-15

Picosecond x-ray measurements relevant to the Livermore Laser Fusion Program are reviewed. Resolved to 15 picoseconds, streak camera detection capabilities extend from 100 eV to higher than 30 keV, with synchronous capabilities in the visible, near infrared, and ultraviolet. Capabilities include automated data retrieval using charge coupled devices (CCD's), absolute x-ray intensity levels, novel cathodes, x-ray mirror/reflector combinations, and a variety of x-ray imaging devices.

18. Measurement of cosmic-ray muons with the Distributed Electronic Cosmic-ray Observatory, a network of smartphones

Vandenbroucke, J.; BenZvi, S.; Bravo, S.; Jensen, K.; Karn, P.; Meehan, M.; Peacock, J.; Plewa, M.; Ruggles, T.; Santander, M.; Schultz, D.; Simons, A. L.; Tosi, D.

2016-04-01

Solid-state camera image sensors can be used to detect ionizing radiation in addition to optical photons. We describe the Distributed Electronic Cosmic-ray Observatory (DECO), an app and associated public database that enables a network of consumer devices to detect cosmic rays and other ionizing radiation. In addition to terrestrial background radiation, cosmic-ray muon candidate events are detected as long, straight tracks passing through multiple pixels. The distribution of track lengths can be related to the thickness of the active (depleted) region of the camera image sensor through the known angular distribution of muons at sea level. We use a sample of candidate muon events detected by DECO to measure the thickness of the depletion region of the camera image sensor in a particular consumer smartphone model, the HTC Wildfire S. The track length distribution is fit better by a cosmic-ray muon angular distribution than an isotropic distribution, demonstrating that DECO can detect and identify cosmic-ray muons despite a background of other particle detections. Using the cosmic-ray distribution, we measure the depletion thickness to be 26.3 ± 1.4 μm. With additional data, the same method can be applied to additional models of image sensor. Once measured, the thickness can be used to convert track length to incident polar angle on a per-event basis. Combined with a determination of the incident azimuthal angle directly from the track orientation in the sensor plane, this enables direction reconstruction of individual cosmic-ray events using a single consumer device. The results simultaneously validate the use of cell phone camera image sensors as cosmic-ray muon detectors and provide a measurement of a parameter of camera image sensor performance which is not otherwise publicly available.

19. Time-resolved measurement of x-ray heating in plastic foils irradiated by intense soft-x-ray pulses

SciTech Connect

Edwards, J.; Dunne, M.; Riley, D.; Taylor, R.; Willi, O. ); Rose, S.J. )

1991-12-30

Intense, soft-x-ray pulses, generated from separate laser-irradiated converters, were used to irradiate plane plastic foils. The x-ray heating was investigated by measuring the temperature histories of chlorinated tracer layers buried at different depths in the targets. The temperature diagonistic was a time-resolved extreme-UV absorption spectroscopy technique using chlorine {ital L}-shell transitions. The temporal temperature profiles were reasonably well reproduced by radiation-hydrocode simulations.

20. Predicting thermal conductivity of rocks from the Los Azufres geothermal field, Mexico, from easily measurable properties

SciTech Connect

Garcia, Alfonso; Contreras, Enrique; Dominquez, Bernardo A.

1988-01-01

A correlation is developed to predict thermal conductivity of drill cores from the Los Azufres geothermal field. Only andesites are included as they are predominant. Thermal conductivity of geothermal rocks is in general scarce and its determination is not simple. Almost all published correlations were developed for sedimentary rocks. Typically, for igneous rocks, chemical or mineral analyses are used for estimating conductivity by using some type of additive rule. This requires specialized analytical techniques and the procedure may not be sufficiently accurate if, for instance, a chemical analysis is to be changed into a mineral analysis. Thus a simple and accurate estimation method would be useful for engineering purposes. The present correlation predicts thermal conductivity from a knowledge of bulk density and total porosity, properties which provide basic rock characterization and are easy to measure. They may be determined from drill cores or cuttings, and the procedures represent a real advantage given the cost and low availability of cores. The multivariate correlation proposed is a quadratic polynomial and represents a useful tool to estimate thermal conductivity of igneous rocks since data on this property is very limited. For porosities between 0% and 25%, thermal conductivity is estimated with a maximum deviation of 22% and a residual mean square deviation of 4.62E-3 n terms of the log{sub 10}(k{rho}{sub b}) variable. The data were determined as part of a project which includes physical, thermal and mechanical properties of drill cores from Los Azufres. For the correlation, sixteen determinations of thermal conductivity, bulk density and total porosity are included. The conductivity data represent the first determinations ever made on these rocks.

1. Cosmic Ray-Air Shower Measurement from Space

NASA Technical Reports Server (NTRS)

Takahashi, Yoshiyuki

1997-01-01

A feasibility study has been initiated to observe from space the highest energy cosmic rays above 1021 eV. A satellite observatory concept, the Maximum-energy Auger (Air)-Shower Satellite (MASS), is recently renamed as the Orbital Wide-angle Collector (OWL) by taking its unique feature of using a very wide field-of-view (FOV) optics. A huge array of imaging devices (about 10(exp 6) pixels) is required to detect and record fluorescent light profiles of cosmic ray cascades in the atmosphere. The FOV of MASS could extend to as large as about 60 in. diameter, which views (500 - 1000 km) of earth's surface and more than 300 - 1000 cosmic ray events per year could be observed above 1020 eV. From far above the atmosphere, the MASS/OWL satellite should be capable of observing events at all angles including near horizontal tracks, and would have considerable aperture for high energy photon and neutrino observation. With a large aperture and the spatial and temporal resolution, MASS could determine the energy spectrum, the mass composition, and arrival anisotropy of cosmic rays from 1020 eV to 1022 eV; a region hitherto not explored by ground-based detectors such as the Fly's Eye and air-shower arrays. MASS/OWL's ability to identify cosmic neutrinos and gamma rays may help providing evidence for the theory which attributes the above cut-off cosmic ray flux to the decay of topological defects. Very wide FOV optics system of MASS/OWL with a large array of imaging devices is applicable to observe other atmospheric phenomena including upper atmospheric lightning. The wide FOV MASS optics being developed can also improve ground-based gamma-ray observatories by allowing simultaneous observation of many gamma ray sources located at different constellations.

2. Ionic conductivity measurement in magnesium aluminate spinel and solid state galvanic cell with magnesium aluminate electrolyte

Lee, Myongjai

This thesis work is about the experimental measurement of electronic and ionic conductivities in the MgAl2O4 spinel at 500˜600°C range and exploring the fundamental origin of solid-state galvanic cell behavior in the cell of Al|MgAl2O4|Mg, Al|MgAl2O 4|C, and Mg|MgAl2O4|C, in which at least one metal electrode in common with the composition of the electrolyte. For the electronic conductivity measurement, we have used the ion-blocking Gold and Carbon electrodes which are inert with both Mg and Al ions to suppress the ionic conduction from the total conduction. DC polarization method was used to measure the conduction through Au|MgAl2O4|Au and C|MgAl2O4|C specimens. The measured electrical conductivity using Au|MgAl2O4|Au and C|MgAl2O4|C specimens showed 10-9.3 ˜ 10-8.4 (O·cm) -1 at 600˜720°C range following the Arrhenius-type relation. These conductivity data are in agreement with reported data obtained from Pt and Ag ion-blocking electrodes deposited on MgAl2O4 specimens. For the ionic conductivity measurement, we have used the non-blocking Al and Mg electrodes for Al and Mg ionic conductivities, respectively. Ionic conductivity measurement of Al and Mg in separate manner has not been reported yet. In both Al|MgAl2O4|Al and Mg|MgAl2O 4|Mg specimens, gradual increase of conduction was observed once at the initial period before it reaches the steady state conduction. By DC method on the range of 580˜650°C, steady state Al ionic conductivity was measured from Al|MgAl2O4|Al specimen showing 10 -7.7 ˜ 10-6.8 (O·cm)-1 with the activation energy of 1.9eV in sigma = sigma0 exp-QRT formula. There was no difference in the conductivity by the change of the atmosphere from 5%H2 + 95%N2 mixed gas to pure Ar gas. So it was confirmed that the oxygen defect chemistry did not play a role. For Mg ionic conductivity Mg|MgAl2O4|Mg specimen was used and the measured conductivity shows 10-6.7 ˜ 10-4.4 (O·cm)-1 at 400˜550°C with the activation energy of 1.44eV at Ar gas

3. A simulation of the measurement of electrical conductivity in randomly generated two-phase rocks.

Mandolesi, Eric; Moorkamp, Max; Jones, Alan G.

2014-05-01

Geological models of the subsurface require detailed data, often unavailable from direct observation or well logs. Hence imaging the subsurface relies on models obtained by interpretation of geophysical data. Several electromagnetic (EM) geophysical methods focus on the EM properties of rocks and sediments to determine a reliable image of the subsurface, while the same electromagnetic properties are directly measured in laboratories. Often these laboratory measurements return equivocal results that are difficult to reconcile with field observations. Recently different numerical approaches have been investigated in order to understand the effects of the geometry and continuity of interconnected pathways of conductors on EM field measurements, often restricting the studies to direct current (DC) sources. Bearing in mind the time-varying nature of the natural electromagnetic sources that play a role in field measurements, we numerically simulate the effects of such EM sources on the conductivity measured on the surface of a randomly generated three-dimensional body embedded in a uniform host by using electromagnetic induction equations, thus simulating a magnetotelluric (MT) survey. A key point in such a simulation is the scalability of the problem: the deeper the target, the longer the period of the EM source is needed. On the other hand, a long period signal ignores small heterogeneous conductors in the target bulk of the material, averaging the different conductivities in a median value. Since most real rocks are poor conductors, we have modeled a two-phase mixture of rock and interconnected conductive elements (representing melts, saline fluids, sulphidic, carbonitic, or metallic sediments, etc.), randomly generated within the background host. We have compared the results from the simulated measurements with the target rock embedded at different depths with electrical conductivity predicted by both Hashin-Shtrikman (HS) bounds and an updated multi-phase Archie

4. High accuracy thermal conductivity measurements near the lambda transition of helium with very high temperature resolution

NASA Technical Reports Server (NTRS)

Fairbank, William M.; Lipa, John A.

1989-01-01

Over the past few years extensive thermal conductivity measurements near the lambda point of helium were made. The original goal of measuring the thermal conductivity with a resolution of t = T/T sub lambda -1 of 3 x 10(-8) was reached, but with somewhat less accuracy than was hoped. Subtle effects in the apparatus near the transition were observed which reduced the ability to interpret the results. Nevertheless, for resolution of t is greater than or equal to 10(-7) reliable data was obtained, extending previous measurements by more than an order of magnitude. Deviations from theoretical predictions were observed for t is less than or equal to 3 x 10(-6) leading to the question of the validity of the present renormalization group analysis of transport properties, at least for the case of helium. This anomaly led to closer examination of the boundary effects in the measurements. During the experiments a totally unexpected effect in the very dilute He-3 - He-4 mixtures was observed which led to the explanation of the anomalous results. The concentration dependence of the thermal conductivity near T sub lambda in the superfluid phase was found to deviate strongly from the predictions. The results gave an independent verification of this behavior and caused reanalysis of the Khalatnikov theory of hydrodynamics of the mixtures. An alternative solution was found which is in better agreement with the experiment.

5. Transient thermal conductivity and colloidal stability measurements of nanofluids by using the 3omega method.

PubMed

Oh, Dong-Wook; Kwon, Ohmyoung; Lee, Joon Sik

2008-10-01

Nanofluid is a mixture of nanoscale particles of metal, metal oxide or carbon nanotube and heat transfer fluids such as water and ethylene glycol. This work presents the application of the 3-omega (3omega) method for measuring the colloidal stability and the transient thermal conductivity of multi-wall carbon nanotube (MWCNT), Al2O3 and TiO2 nanoparticles suspended in water or ethylene glycol. The microfabricated 3omega device is verified by comparing the measured thermal conductivities of pure fluids with the table values. After the validation, the transient thermal responses of the nanofluids are measured to evaluate the colloidal stability. All of Al2O3 nanofluid samples show a clear sign of sedimentation while the acid-treated MWCNT (tMWCNT) nanofluid and a couple of TiO2 nanofluids with pH control or surfactant addition are found to have excellent colloidal stability. The thermal conductivities of tMWCNT nanofluids in the de-ionized water and ethylene glycol are measured, which are found to be in good agreement with previous data. PMID:19198364

6. Photoacoustic infrared spectroscopy for conducting gas tracer tests and measuring water saturations in landfills

SciTech Connect

Jung, Yoojin; Han, Byunghyun; Mostafid, M. Erfan; Chiu, Pei; Yazdani, Ramin; Imhoff, Paul T.

2012-02-15

Highlights: Black-Right-Pointing-Pointer Photoacoustic infrared spectroscopy tested for measuring tracer gas in landfills. Black-Right-Pointing-Pointer Measurement errors for tracer gases were 1-3% in landfill gas. Black-Right-Pointing-Pointer Background signals from landfill gas result in elevated limits of detection. Black-Right-Pointing-Pointer Technique is much less expensive and easier to use than GC. - Abstract: Gas tracer tests can be used to determine gas flow patterns within landfills, quantify volatile contaminant residence time, and measure water within refuse. While gas chromatography (GC) has been traditionally used to analyze gas tracers in refuse, photoacoustic spectroscopy (PAS) might allow real-time measurements with reduced personnel costs and greater mobility and ease of use. Laboratory and field experiments were conducted to evaluate the efficacy of PAS for conducting gas tracer tests in landfills. Two tracer gases, difluoromethane (DFM) and sulfur hexafluoride (SF{sub 6}), were measured with a commercial PAS instrument. Relative measurement errors were invariant with tracer concentration but influenced by background gas: errors were 1-3% in landfill gas but 4-5% in air. Two partitioning gas tracer tests were conducted in an aerobic landfill, and limits of detection (LODs) were 3-4 times larger for DFM with PAS versus GC due to temporal changes in background signals. While higher LODs can be compensated by injecting larger tracer mass, changes in background signals increased the uncertainty in measured water saturations by up to 25% over comparable GC methods. PAS has distinct advantages over GC with respect to personnel costs and ease of use, although for field applications GC analyses of select samples are recommended to quantify instrument interferences.

7. Optical layer development for thin films thermal conductivity measurement by pulsed photothermal radiometry

Martan, J.

2015-01-01

Measurement of thermal conductivity and volumetric specific heat of optically transparent thin films presents a challenge for optical-based measurement methods like pulsed photothermal radiometry. We present two approaches: (i) addition of an opaque optical layer to the surface and (ii) approximate correction of the mathematical model to incorporate semitransparency of the film. Different single layer and multilayer additive optical layers were tested. The materials of the optical layers were chosen according to analysis and measurement of their optical properties: emissivity and absorption coefficient. Presented are thermal properties' measurement results for 6 different thin films with wide range of thermal conductivity in three configurations of surface: as deposited, added Ti layer, and added Ti/TiAlSiN layer. Measurements were done in dependence on temperature from room temperature to 500 °C. The obtained thermal effusivity evolution in time after the laser pulse shows different effects of the surface layers: apparent effusivity change and time delay. Suitability of different measurement configurations is discussed and results of high temperature testing of different optical layers are presented.

8. Optical layer development for thin films thermal conductivity measurement by pulsed photothermal radiometry.

PubMed

Martan, J

2015-01-01

Measurement of thermal conductivity and volumetric specific heat of optically transparent thin films presents a challenge for optical-based measurement methods like pulsed photothermal radiometry. We present two approaches: (i) addition of an opaque optical layer to the surface and (ii) approximate correction of the mathematical model to incorporate semitransparency of the film. Different single layer and multilayer additive optical layers were tested. The materials of the optical layers were chosen according to analysis and measurement of their optical properties: emissivity and absorption coefficient. Presented are thermal properties' measurement results for 6 different thin films with wide range of thermal conductivity in three configurations of surface: as deposited, added Ti layer, and added Ti/TiAlSiN layer. Measurements were done in dependence on temperature from room temperature to 500 °C. The obtained thermal effusivity evolution in time after the laser pulse shows different effects of the surface layers: apparent effusivity change and time delay. Suitability of different measurement configurations is discussed and results of high temperature testing of different optical layers are presented. PMID:25638108

9. Optical layer development for thin films thermal conductivity measurement by pulsed photothermal radiometry

SciTech Connect

Martan, J.

2015-01-15

Measurement of thermal conductivity and volumetric specific heat of optically transparent thin films presents a challenge for optical-based measurement methods like pulsed photothermal radiometry. We present two approaches: (i) addition of an opaque optical layer to the surface and (ii) approximate correction of the mathematical model to incorporate semitransparency of the film. Different single layer and multilayer additive optical layers were tested. The materials of the optical layers were chosen according to analysis and measurement of their optical properties: emissivity and absorption coefficient. Presented are thermal properties’ measurement results for 6 different thin films with wide range of thermal conductivity in three configurations of surface: as deposited, added Ti layer, and added Ti/TiAlSiN layer. Measurements were done in dependence on temperature from room temperature to 500 °C. The obtained thermal effusivity evolution in time after the laser pulse shows different effects of the surface layers: apparent effusivity change and time delay. Suitability of different measurement configurations is discussed and results of high temperature testing of different optical layers are presented.

10. Measurement of thin film thermal conductivity using the laser flash method.

PubMed

Ruoho, Mikko; Valset, Kjetil; Finstad, Terje; Tittonen, Ilkka

2015-05-15

We present a method to measure the in-plane thermal conductivity of thin films by the laser flash technique. The method uses a well-defined structure for the analysis. We have realized the structure by conformal deposition of ZnO films of different thicknesses using atomic layer deposition onto a 20 μm thick ion track etched polycarbonate membrane as substrate. By using this procedure we could determine the thermal conductivity of the deposited thin film from the total thermal diffusivity of the nanocomposite structures. The method has been used to obtain the in-plane thermal conductivity of the deposited ZnO layers within the thickness range of less than 100 nm. PMID:25900909

11. Measurement of conductivity and permittivity on samples sealed in nuclear magnetic resonance tubes

SciTech Connect

Huang, W.; Angell, C. A.; Yarger, J. L.; Richert, R.

2013-07-15

We present a broadband impedance spectroscopy instrument designed to measure conductivity and/or permittivity for samples that are sealed in glass tubes, such as the standard 5 mm tubes used for nuclear magnetic resonance experiments. The calibrations and corrections required to extract the dielectric properties of the sample itself are outlined. It is demonstrated that good estimates of the value of dc-conductivity can be obtained even without correcting for the effects of glass or air on the overall impedance. The approach is validated by comparing data obtained from samples sealed in nuclear magnetic resonance tubes with those from standard dielectric cells, using glycerol and butylmethylimidazolium-hexafluorophosphate as respective examples of a molecular and an ionic liquid. This instrument and approach may prove useful for other studies of permittivity and conductivity where contact to the metal electrodes or to the ambient atmosphere needs to be avoided.

12. Electrical conductivity measurements of aqueous fluids under pressure with a hydrothermal diamond anvil cell

Ni, Huaiwei; Chen, Qi; Keppler, Hans

2014-11-01

Electrical conductivity data of aqueous fluids under pressure can be used to derive the dissociation constants of electrolytes, to assess the effect of ionic dissociation on mineral solubility, and to interpret magnetotelluric data of earth's interior where a free fluid phase is present. Due to limitation on the tensile strength of the alloy material of hydrothermal autoclaves, previous measurements of fluid conductivity were mostly restricted to less than 0.4 GPa and 800 °C. By adapting a Bassett-type hydrothermal diamond anvil cell, we have developed a new method for acquiring electrical conductivity of aqueous fluids under pressure. Our preliminary results for KCl solutions using the new method are consistent with literature data acquired with the conventional method, but the new method has great potential for working in a much broader pressure range.

13. Insulator-protected mechanically controlled break junctions for measuring single-molecule conductance in aqueous environments

Muthusubramanian, N.; Galan, E.; Maity, C.; Eelkema, R.; Grozema, F. C.; van der Zant, H. S. J.

2016-07-01

We present a method to fabricate insulated gold mechanically controlled break junctions (MCBJ) by coating the metal with a thin layer of aluminum oxide using plasma enhanced atomic layer deposition. The Al2O3 thickness deposited on the MCBJ devices was varied from 2 to 15 nm to test the suppression of leakage currents in deionized water and phosphate buffered saline. Junctions coated with a 15 nm thick oxide layer yielded atomically sharp electrodes and negligible conductance counts in the range of 1 to 10-4 G0 (1 G0 = 77 μS), where single-molecule conductances are commonly observed. The insulated devices were used to measure the conductance of an amphiphilic oligophenylene ethynylene derivative in deionized water.

14. Simultaneous measurement of electrical and thermal conductivities of suspended monolayer graphene

Wang, Haidong; Kurata, Kosaku; Fukunaga, Takanobu; Ago, Hiroki; Takamatsu, Hiroshi; Zhang, Xing; Ikuta, Tatsuya; Takahashi, Koji; Nishiyama, Takashi; Takata, Yasuyuki

2016-06-01

We measured both in-plane electrical and thermal properties of the same suspended monolayer graphene using a novel T-type sensor method. At room temperature, the values are about 240 000 Ω-1 m-1 and 2100 W m-1 K-1 for the electrical and thermal conductivities, respectively. Based on the Wiedemann-Franz law, the electrons have negligible contribution to the thermal conductivity of graphene, while the in-plane LA and TA modes phonons are the dominant heat carriers. In monolayer graphene, the absence of layer-layer and layer-substrate interactions enhances the contribution of long wave-length phonons to the heat transport and increases the thermal conductivity accordingly. The reported method and experimental data of suspended monolayer graphene are useful for understanding the basic physics and designing the future graphene electronic devices.

15. Measurement of thin film thermal conductivity using the laser flash method

Ruoho, Mikko; Valset, Kjetil; Finstad, Terje; Tittonen, Ilkka

2015-05-01

We present a method to measure the in-plane thermal conductivity of thin films by the laser flash technique. The method uses a well-defined structure for the analysis. We have realized the structure by conformal deposition of ZnO films of different thicknesses using atomic layer deposition onto a 20 μm thick ion track etched polycarbonate membrane as substrate. By using this procedure we could determine the thermal conductivity of the deposited thin film from the total thermal diffusivity of the nanocomposite structures. The method has been used to obtain the in-plane thermal conductivity of the deposited ZnO layers within the thickness range of less than 100 nm.

16. Measurement of conductivity and permittivity on samples sealed in nuclear magnetic resonance tubes

Huang, W.; Angell, C. A.; Yarger, J. L.; Richert, R.

2013-07-01

We present a broadband impedance spectroscopy instrument designed to measure conductivity and/or permittivity for samples that are sealed in glass tubes, such as the standard 5 mm tubes used for nuclear magnetic resonance experiments. The calibrations and corrections required to extract the dielectric properties of the sample itself are outlined. It is demonstrated that good estimates of the value of dc-conductivity can be obtained even without correcting for the effects of glass or air on the overall impedance. The approach is validated by comparing data obtained from samples sealed in nuclear magnetic resonance tubes with those from standard dielectric cells, using glycerol and butylmethylimidazolium-hexafluorophosphate as respective examples of a molecular and an ionic liquid. This instrument and approach may prove useful for other studies of permittivity and conductivity where contact to the metal electrodes or to the ambient atmosphere needs to be avoided.

17. Electronmagnetic induction probe calibration for electrical conductivity measurements and moisture content determination of Hanford high level waste

SciTech Connect

Wittekind, W.D., Westinghouse Hanford

1996-05-23

Logic of converting EMI measured electrical conductivity to moisture with expected uncertainty. Estimates from present knowledge, assumptions, and measured data. Archies Law has been used since the 1940s to relate electrical conductivity in porous media to liquid volume fraction. Measured electrical conductivity to moisture content uses: Porosity, Interstitial liquid electrical conductivity, Solid particle density,Interstitial liquid density, and interstitial liquid water content. The uncertainty of assumed values is calculated to determine the final moisture wt.% result uncertainty.

18. Spectroscopic Measurement of L X-rays Emitted by Transuranium Elements by Using TES Microcalorimeter

Maeda, M.; Maehata, K.; Iyomoto, N.; Ishibashi, K.; Takasaki, K.; Nakamura, K.; Aoki, K.; Mitsuda, K.; Tanaka, K.

2014-09-01

Energy spectra of L X-rays emitted by Np and uranium isotopes progenies of Am and plutonium isotopes were measured by a transition edge sensor (TES) microcalorimeter for demonstration of peak separation with high energy resolution. L X-ray photons emitted by transuranium (TRU) elements can to be utilized for a nondestructive TRU monitor. Major L X-ray peaks are clearly distinguished in the energy spectrum of L X-rays obtained by the simultaneous measurement for radiation sources of Am and plutonium isotopes. The value of full width at half maximum energy resolution is 60.21 eV for a peak corresponding to Np L X -rays of 17.751 keV in Am source measurement. Comparable energy resolutions were obtained in other experiments. This measurement demonstrated separation of Am and plutonium isotopes by L X-ray spectroscopy using TES microcalorimeter.

19. Measurements of γ-ray Energy and Multiplicity from 235U(nthermal) using STEFF

Pollitt, A. J.; Smith, A. G.; Tsekhanovich, I.; Dare, J. A.; Murray, L.

2015-05-01

The amount of energy carried by γ-rays during the fission process is an important consideration when developing new reactor designs. Many studies of γ-ray energy and multiplicity, from a multitude of fissioning systems, were measured during the 1970s. However the data from such experiments largely underestimates the heating effect caused by γ-rays in the structure of a reactor. It is therefore essential to obtain more accurate measurements of the energy carried during γ-ray emission. As such, the OECD Nuclear Energy Agency has put out a high priority request [1] for measurements of the mean γ-ray energy and multiplicity to an accuracy better than 7.5 percent from several fissioning systems; including 235U(nthermal). Measurements of the rays from these fissioning nuclei were performed with the SpecTrometer for Exotic Fission Fagments (STEFF).

20. Gamma rays and cosmic rays at Venus: The Pioneer Venus gamma ray detector and considerations for future measurements

Lorenz, Ralph D.; Lawrence, David J.

2015-05-01

We draw attention to, and present a summary archive of the data from, the Pioneer Venus Orbiter Gamma-ray Burst Detector (OGBD), an instrument not originally conceived with Venus science in mind. We consider the possibility of gamma-ray flashes generated by lightning and model the propagation of gamma rays in the Venusian atmosphere, finding that if gamma rays originate at the upper range of reported cloud top altitudes (75 km altitude), they may be attenuated by factors of only a few, whereas from 60 km altitude they are attenuated by over two orders of magnitude. The present archive is too heavily averaged to reliably detect such a source (and we appeal to investigators who may have retained a higher-resolution archive), but the data do provide a useful and unique record of the cosmic ray flux at Venus 1978-1993. We consider other applications of future orbital gamma ray data, such as atmospheric occultations and the detection of volcanic materials injected high in the atmosphere.

1. Standardisation of 169Yb and precise measurement of gamma-ray emission probabilities

Miyahara, Hiroshi; Nagata, Hideaki; Furusawa, Takayoshi; Murakami, Naotaka; Mori, Chizuo; Takeuchi, Norio; Genka, Tsuguo

1999-01-01

The gamma-ray emission probabilities of 169Yb were determined directly from the disintegration rate and the gamma-ray intensities. The disintegration rates of 169Yb sources were measured by using a 4πβ(ppc)-γ(HPGe) coincidence system with resolving times of both 2.06 and 5.66 μs and the γ-ray intensities were measured with HPGe detectors. The measured γ-ray emission probabilities agreed relatively well with those reported by Funck et al. (Int. J. Appl. Radiat. Isotopes 34 (1983) 1215) but their results were slightly larger. The uncertainties were improved.

2. Measurement of local gain and electron density in an yttrium x-ray laser amplifier

SciTech Connect

Cauble, R.; Da Silva, L.B.; Barbee, T.Jr.; Celliers, P.; Decker, C.; London, R.A.; Moreno, J.C.; Trebes, J.E.; Wan, A.S.; Weber, F.

1996-05-01

X-ray lasers have measured average gains significantly less than calculated and a persistently low level of spatial coherence. We have used an X-ray laser both as an injected signal to a short X-ray laser amplifier and as an interferometer beam to measure two dimensional local gain and density profiles of the X-ray laser plasma with near-1- mm resolution. The measured local gain is in agreement with atomic models, but its gain is unexpectedly spatially inhomogeneous. This inhomogeneity explains the low level of spatial coherence observed and helps explain the disparity between observed and simulated gains.

3. Fission prompt gamma-ray multiplicity distribution measurements and simulations at DANCE

SciTech Connect

Chyzh, A; Wu, C Y; Ullmann, J; Jandel, M; Bredeweg, T; Couture, A; Norman, E

2010-08-24

The nearly energy independence of the DANCE efficiency and multiplicity response to {gamma} rays makes it possible to measure the prompt {gamma}-ray multiplicity distribution in fission. We demonstrate this unique capability of DANCE through the comparison of {gamma}-ray energy and multiplicity distribution between the measurement and numerical simulation for three radioactive sources {sup 22}Na, {sup 60}Co, and {sup 88}Y. The prospect for measuring the {gamma}-ray multiplicity distribution for both spontaneous and neutron-induced fission is discussed.

4. An energy and intensity monitor for X-ray absorption near-edge structure measurements

de Jonge, Martin D.; Paterson, David; McNulty, Ian; Rau, Christoph; Brandes, Jay A.; Ingall, Ellery

2010-07-01

An in-line X-ray beam energy and intensity monitor has been developed for use in focussed X-ray absorption near-edge spectroscopy (XANES) measurements. The monitor uses only the X-ray intensity that would otherwise bypass our zone-plate focussing optic and relies on a measurement of photoemission current. The monitor is inexpensive, easy to align, and provides valuable feedback about the X-ray energy. Operation of the monitor is demonstrated for measurements of phosphorus XANES. The precision of the energy determination is around 0.5 eV.

5. Electrical conductivity measurement of MgCO3 up to 6 GPa and 1000 K

Mibe, K.; Ono, S.

2012-04-01

Magnesite, MgCO3, is a naturally occurring carbonate mineral and is stable over a wide range of pressure and temperature. It is known that magnesite is one of the important host phases of carbon in the Earth's deep interior. A knowledge of how magnesite's electrical properties vary as a function of pressure and temperature will be important in interpreting the observed electrical conductivity map of the Earth's interior. We, therefore, measured the electrical conductivity of polycrystalline magnesite at pressures 3-6 GPa at high temperatures using complex impedance spectroscopy in a multi-anvil high-pressure apparatus. Synthetic powdered magnesite (MgCO3)(purity > 99.5%) was used as the starting material. The measured electrical conductivity increased with increasing pressure. The activation enthalpy calculated in the temperature range 650-1000 K also increased with increasing pressure. The effect of pressure was interpreted as being the activation volume in the Arrhenius equation, and the fitted data gave an activation energy and volume of 1.76 ± 0.03 eV and -3.95 ± 0.78 cm3/mole, respectively. The negative activation volume and relatively large activation energy observed in this study suggests that the hopping of large polarons is the dominant mechanism for the electrical conductivity over the pressure and temperature range investigated.

6. Effects of Contact Resistance on Electrical Conductivity Measurements of SiC-Based Materials

SciTech Connect

Youngblood, Gerald E.; Thomsen, Edwin C.; Henager, Charles H.

2012-04-17

A combination 2/4-probe method was used to measure electrical resistances across a pure, monolithic CVD-SiC disc sample with contact resistance at the SiC/metallic electrode interfaces. By comparison of the almost simultaneous 2/4-probe measurements, the specific contact resistance and its temperature dependence were determined for two types (sputtered gold and porous nickel) electrodes from RT to ~700°C. The specific contact resistance values (Rc) behaved similarly for each type of metallic electrode: Rc >~1000 Ω-cm2 at RT, decreasing continuously to ~1-10 Ω-cm2 at 700°C. The temperature dependence of the inverse Rc indicated thermally activated electrical conduction across the SiC/metallic interface with an apparent activation energy of ~0.3 eV. For the flow channel insert application in a fusion reactor blanket, contact resistance potentially could reduce the transverse electrical conductivity by ~1/2.

7. A comparison of two transient methods of measuring thermal conductivity of particulate samples.

NASA Technical Reports Server (NTRS)

Scott, R. W.; Fountain, J. A.; West, E. A.

1973-01-01

A comparison is made of the line source (LS) method and the differential line source (DLS) method of measuring thermal conductivity of particulate materials in vacuum. The DLS method requires more instrumentation in the measuring circuitry (an additional amplifier and a differentiating circuit), but since it does not require a stable temperature to initiate a test, it does not need a sample temperature control system. DLS tests can be taken as the temperature in the samples is rising from liquid nitrogen temperature to room temperature. This eliminates the practice of extrapolating thermal conductivity over this large temperature range. Also, the advantages of reduced test time, data reduction time, and small sample temperature rise enable the experimenter to take about 7-12 DLS tests in the time of 2 LS tests. Test data from the two methods agree very well.

8. Measurement of temperature-dependent viscosity and thermal conductivity of alumina and titania thermal oil nanofluids

Cieśliński, Janusz T.; Ronewicz, Katarzyna; Smoleń, Sławomir

2015-12-01

In this study the results of simultaneous measurements of dynamic viscosity, thermal conductivity, electrical conductivity and pH of two nanofluids, i.e., thermal oil/Al2O3 and thermal oil/TiO2 are presented. Thermal oil is selected as a base liquid because of possible application in ORC systems as an intermediate heating agent. Nanoparticles were tested at the concentration of 0.1%, 1%, and 5% by weight within temperature range from 20 °C to 60 °C. Measurement devices were carefully calibrated by comparison obtained results for pure base liquid (thermal oil) with manufacturer's data. The results obtained for tested nanofluids were compared with predictions made by use of existing models for liquid/solid particles mixtures.

9. Conductive-cooled 2-micron laser development for wind and CO2 measurements

Mizutani, Kohei; Ishii, Shoken; Yasui, Motoaki; Itabe, Toshikazu; Sato, Atsushi; Asai, Kazuhiro; Fukuoka, Hirotake; Ishikawa, Takayoshi

2012-11-01

We have developing two types of 2micron conductive-cooled lasers for wind and CO2 measurements. One type of lasers is side pumped Tm,Ho:YLF laser operated at 20-40Hz. The laser rod is cooled down to -80C and laser diodes are operated at normal temperature in a vacuum container. With this type of laser, we have built up a coherent lidar system which is used to measure wind and CO2 concentration. Ho:YLF laser end-pumped by Tm:fiber laser is another type oscillator which will be operated at high repetition rate of 200-300 Hz in normal temperature. The laser will have an amplifier. These lasers are conductive-cooled, solid-state, eye-safe and suitable for space applications.

10. Thermal conductivity and viscosity measurements of ethylene glycol-based Al2O3 nanofluids

PubMed Central

2011-01-01

The dispersion and stability of nanofluids obtained by dispersing Al2O3 nanoparticles in ethylene glycol have been analyzed at several concentrations up to 25% in mass fraction. The thermal conductivity and viscosity were experimentally determined at temperatures ranging from 283.15 K to 323.15 K using an apparatus based on the hot-wire method and a rotational viscometer, respectively. It has been found that both thermal conductivity and viscosity increase with the concentration of nanoparticles, whereas when the temperature increases the viscosity diminishes and the thermal conductivity rises. Measured enhancements on thermal conductivity (up to 19%) compare well with literature values when available. New viscosity experimental data yield values more than twice larger than the base fluid. The influence of particle size on viscosity has been also studied, finding large differences that must be taken into account for any practical application. These experimental results were compared with some theoretical models, as those of Maxwell-Hamilton and Crosser for thermal conductivity and Krieger and Dougherty for viscosity. PMID:21711737

11. Thermal conductivity of a film of single walled carbon nanotubes measured with infrared thermal imager

Feng, Ya; Inoue, Taiki; Xiang, Rong; Chiashi, Shohei; Maruyama, Shigeo

Heat dissipation has restricted the modern miniaturization trend with the development of electronic devices. Theoretically proven to be with high axial thermal conductivity, single walled carbon nanotubes (SWNT) have long been expected to cool down the nanoscale world. Even though the tube-tube contact resistance limits the capability of heat transfer of the bulk film, the high intrinsic thermal conductivity of SWNT still glorify the application of films of SWNT network as a thermal interface material. In this work, we proposed a new method to straightly measure the thermal conductivity of SWNT film. We bridged two cantilevered Si thin plate with SWNT film, and kept a steady state heat flow in between. With the infrared camera to record the temperature distribution, the Si plates with known thermal conductivity can work as a reference to calculate the heat flux going through the SWNT film. Further, the thermal conductivity of the SWNT film can be obtained through Fourier's law after deducting the effect of thermal radiation. The sizes of the structure, the heating temperature, the vacuum degree and other crucial impact factors are carefully considered and analyzed. The author Y. F. was supported through the Advanced Integration Science Innovation Education and Research Consortium Program by the Ministry of Education, Culture, Sport, Science and Technology.

12. Conductivities of pig dermis and subcutaneous fat measured with rectangular pulse electrical current

SciTech Connect

Cheng, K. |; Tarjan, P.P.; Mertz, P.M.

1996-12-31

The authors examined experimentally the relationship between perpendicular and tangential electrical conductivities, {sigma}, and peak current density J, in pig skin dermis and subcutaneous fat specimens by using a four-electrode measuring system with rectangular pulse electrical current (RPEC). They also investigated the relationship of the conductivity, {sigma}, vs. pulse rate, f. The rates were selected at 8, 32, 64, and 128 pulses per second (pps), and the pulse width was fixed at 140 {micro}s. These values are often used in vivo to enhance cutaneous regeneration with RPEC stimulation. It was found that the conductivities may be approximated to be {sigma}{sub d} = [{sigma}{sub dx}{sigma}{sub dy}{sigma}{sub dz}] = [0.38 S/m 0.38 S/m 0.27 S/m] for the skin dermis and {sigma}{sub f} = [{sigma}{sub fx}{sigma}{sub fy}{sigma}{sub fz}] = [0.074 S/m 0.074 S/m 0.045 S/m] for the subcutaneous fat in the conditions of this experiment. These findings implies that the conductivities of the pig skin dermis and subcutaneous fat are anisotropic, i.e., {sigma}{sub x} = {sigma}{sub y} {ne} {sigma}{sub z}. It was also found that the conductivities are independent of current density and pulse rate in the current range from 20 {micro}A/cm{sup 2} to 120 mA/cm{sup 2}.

13. Estimating Concentrations of Road-Salt Constituents in Highway-Runoff from Measurements of Specific Conductance

USGS Publications Warehouse

Granato, Gregory E.; Smith, Kirk P.

1999-01-01

Discrete or composite samples of highway runoff may not adequately represent in-storm water-quality fluctuations because continuous records of water stage, specific conductance, pH, and temperature of the runoff indicate that these properties fluctuate substantially during a storm. Continuous records of water-quality properties can be used to maximize the information obtained about the stormwater runoff system being studied and can provide the context needed to interpret analyses of water samples. Concentrations of the road-salt constituents calcium, sodium, and chloride in highway runoff were estimated from theoretical and empirical relations between specific conductance and the concentrations of these ions. These relations were examined using the analysis of 233 highwayrunoff samples collected from August 1988 through March 1995 at four highway-drainage monitoring stations along State Route 25 in southeastern Massachusetts. Theoretically, the specific conductance of a water sample is the sum of the individual conductances attributed to each ionic species in solution-the product of the concentrations of each ion in milliequivalents per liter (meq/L) multiplied by the equivalent ionic conductance at infinite dilution-thereby establishing the principle of superposition. Superposition provides an estimate of actual specific conductance that is within measurement error throughout the conductance range of many natural waters, with errors of less than ?5 percent below 1,000 microsiemens per centimeter (?S/cm) and ?10 percent between 1,000 and 4,000 ?S/cm if all major ionic constituents are accounted for. A semi-empirical method (adjusted superposition) was used to adjust for concentration effects-superposition-method prediction errors at high and low concentrations-and to relate measured specific conductance to that calculated using superposition. The adjusted superposition method, which was developed to interpret the State Route 25 highway-runoff records, accounts for

14. Construction of an ionization chamber for the measurement of dose of low energy x-rays

SciTech Connect

Perez, Y. B. Alcantara; Jimenez, F. J. Ramirez

2008-08-11

We designed and constructed the prototype of an ionization chamber to measure the dose of an X-ray tube with Molybdenum anode. This X-ray tube is located in the Physics department at CINVESTAV and is used for medical physics purposes in the imaging area. The ionization chamber is designed to measure doses on biological samples exposed to X-rays and will be applied in radiation protection studies.

15. Summary of round robin measurements of radiation induced conductivity in Wesgo AL995 alumina

SciTech Connect

Zinkle, S.J.

1996-10-01

This existing data on radiation induced conductivity (RIC) measurements performed on the same heat of the IEA reference ceramic insulator are summarized. Six different sets of RIC measurements have been performed on Wesgo AL995 at dose rates between 10 Gy/s and 1 MGy/s. In general, good agreement was obtained between the different groups of researchers. The data indicate that the RIC at a test temperature of 400-500{degrees}C is approximately linear with ionizing dose rate up to {approximately}1000 Gy/s, and exhibits an approximately square root dependence on dose rate between 1 kGy/s and 1 MGy/s.

16. A new TDR multiplexing system for reliable electrical conductivity and soil water content measurements

Weihermueller, Lutz; Huisman, Sander; Hermes, Normen; Pickel, Stefanie; Vereecken, Harry

2013-04-01

Time domain reflectometry (TDR) is a standard method to estimate soil water content and bulk soil electrical conductivity. In many applications, several TDR probes are installed in soil columns or field setups, and they are measured using a multiplexing system. It has been reported that commercially available multiplexers share a common ground, which might lead to inaccurate TDR measurements when probes are installed close together or at sites with high electromagnetic noise. Therefore, a new eight-channel differential multiplexer (50C81-SDM) was developed that allows communication with standard TDR equipment. The 50C81-SDM multiplexer was tested using measurement in electrolyte solutions and a sand tank. In contrast to multiplexers with a common ground, they showed no interference of closely spaced TDR probes. Measurements at a test site also showed the applicability of the 50C81-SDM multiplexer in an environment contaminated with high electromagnetic noise.

17. Measurement of Apparent Thermal Conductivity and Laser Absorptivity of Individual Carbon Fibers

Liu, Jin-hui; Wang, Hai-dong; Hu, Yu-dong; Ma, Wei-gang; Zhang, Xing

2015-11-01

The apparent thermal conductivity (ATC) and laser absorptivity (α ) are important properties of miro/nano materials but a challenge to measure due to their small size. In this paper, a simple and effective method employing Raman spectroscopy together with electrical heating is developed to measure thermal properties of micro/nano wires. The sample used in the experiment is very simple and easy to fabricate. The ATC is obtained by measuring the temperature difference induced by changing the electrical heating power; the laser heating power is neither neglected nor needed. Using the laser heating temperature rise and the measured ATC, the absorbed laser power can be calculated. Three individual carbon fibers were studied using the presented method.

18. A setup for simultaneously measureing the thermopower and electrical conductivity of μm-thickness specimens

Chen, Chih-Ting; Lee, P. C.; Chen, Y. Y.; Harutyungyan, Sergey

2008-03-01

We report the concept and configuration of our new setup for measurement of thermopower and electrical conductivity for μm-thickness specimens, especially for thermoelectric materials. It is very difficult and tedious to accurately measure the thermopower for specimens with thickness less than ˜100 μm due to the limitations of smallest size ˜25μm of thermocouples. Such are obvious when applied to the measurement of nanowire arrays and multilayer . In order to resolve these difficulties, we developed a new setup with integration of Pt-film thermometers and electrical electrodes on two sapphire chips used to clamp specimens with thickness >40 μm and cross section 2 x 3 mm^2. Use this setup the thermopower and electric conductivity can be measured simultaneously for temperature range 20-400 K. The advantages of the setup are (1) accuracy: the real temperatures of both sides of the sample can be obtained. (2) convenience for loading samples: just assemble the sample between the two microchips and make sure of a good thermal and electrical contacts. A Bi2Te3 nanowire array in AAO template was tested, the thermopower ˜ 50μV/K was measured for diameter ˜ 60 nm of nanowires.

19. Test Rig for High-Temperature Thermopower and Electrical Conductivity Measurements

Boldrini, S.; Famengo, A.; Montagner, F.; Battiston, S.; Fiameni, S.; Fabrizio, M.; Barison, S.

2013-07-01

A high-temperature test rig to simultaneously measure electrical conductivity and thermopower is described. The apparatus allows to perform measurements in a controlled atmosphere or vacuum to protect oxygen-sensitive materials. A spring-loaded mounting placed in the cold zone reduces the thermal contact resistance between the sample and two metallic blocks (the hot side and the heat sink) even at high temperatures. The hot-side metal block is periodically heated to obtain the thermopower from the slope of Δ V versus Δ T. Conductivity is measured before each thermopower measurement by a linear four-wire method. The automatic data acquisition and analysis are controlled by a LabView-based interface. Two interchangeable setups are possible. The first one uses silver blocks and K-type thermocouples and is suitable for temperatures from 300 K to about 1000 K. The second one uses W blocks and S-type thermocouples to allow higher-temperature measurements since all the hot-zone parts are made of Al2O3, Pt or W. The device was tested using PdAg alloy and Ni rods and, for the low-temperature range, the NIST standard reference material 3451 (bismuth telluride), strictly confirming the reference data.

20. Apparatus Measures Thermal Conductance Through a Thin Sample from Cryogenic to Room Temperature

NASA Technical Reports Server (NTRS)

Tuttle, James G.

2009-01-01

An apparatus allows the measurement of the thermal conductance across a thin sample clamped between metal plates, including thermal boundary resistances. It allows in-situ variation of the clamping force from zero to 30 lb (133.4 N), and variation of the sample temperature between 40 and 300 K. It has a special design feature that minimizes the effect of thermal radiation on this measurement. The apparatus includes a heater plate sandwiched between two identical thin samples. On the side of each sample opposite the heater plate is a cold plate. In order to take data, the heater plate is controlled at a slightly higher temperature than the two cold plates, which are controlled at a single lower temperature. The steady-state controlling power supplied to the hot plate, the area and thickness of samples, and the temperature drop across the samples are then used in a simple calculation of the thermal conductance. The conductance measurements can be taken at arbitrary temperatures down to about 40 K, as the entire setup is cooled by a mechanical cryocooler. The specific geometry combined with the pneumatic clamping force control system and the steady-state temperature control approach make this a unique apparatus.

1. Conductive shield for ultra-low-field magnetic resonance imaging: Theory and measurements of eddy currents

PubMed Central

Zevenhoven, Koos C. J.; Busch, Sarah; Hatridge, Michael; Öisjöen, Fredrik; Ilmoniemi, Risto J.; Clarke, John

2014-01-01

Eddy currents induced by applied magnetic-field pulses have been a common issue in ultra-low-field magnetic resonance imaging. In particular, a relatively large prepolarizing field—applied before each signal acquisition sequence to increase the signal—induces currents in the walls of the surrounding conductive shielded room. The magnetic-field transient generated by the eddy currents may cause severe image distortions and signal loss, especially with the large prepolarizing coils designed for in vivo imaging. We derive a theory of eddy currents in thin conducting structures and enclosures to provide intuitive understanding and efficient computations. We present detailed measurements of the eddy-current patterns and their time evolution in a previous-generation shielded room. The analysis led to the design and construction of a new shielded room with symmetrically placed 1.6-mm-thick aluminum sheets that were weakly coupled electrically. The currents flowing around the entire room were heavily damped, resulting in a decay time constant of about 6 ms for both the measured and computed field transients. The measured eddy-current vector maps were in excellent agreement with predictions based on the theory, suggesting that both the experimental methods and the theory were successful and could be applied to a wide variety of thin conducting structures. PMID:24753629

2. Measures of skin conductance and heart rate in alcoholic men and women during memory performance

PubMed Central

Poey, Alan; Ruiz, Susan Mosher; Marinkovic, Ksenija; Oscar-Berman, Marlene

2015-01-01

We examined abnormalities in physiological responses to emotional stimuli associated with long-term chronic alcoholism. Skin conductance responses (SCR) and heart rate (HR) responses were measured in 32 abstinent alcoholic (ALC) and 30 healthy nonalcoholic (NC) men and women undergoing an emotional memory task in an MRI scanner. The task required participants to remember the identity of two emotionally-valenced faces presented at the onset of each trial during functional magnetic resonance imaging (fMRI) scanning. After viewing the faces, participants saw a distractor image (an alcoholic beverage, nonalcoholic beverage, or scrambled image) followed by a single probe face. The task was to decide whether the probe face matched one of the two encoded faces. Skin conductance measurements (before and after the encoded faces, distractor, and probe) were obtained from electrodes on the index and middle fingers on the left hand. HR measurements (beats per minute before and after the encoded faces, distractor, and probe) were obtained by a pulse oximeter placed on the little finger on the left hand. We expected that, relative to NC participants, the ALC participants would show reduced SCR and HR responses to the face stimuli, and that we would identify greater reactivity to the alcoholic beverage stimuli than to the distractor stimuli unrelated to alcohol. While the beverage type did not differentiate the groups, the ALC group did have reduced skin conductance and HR responses to elements of the task, as compared to the NC group. PMID:26020002

3. On-chip electrochemical microsystems for measurements of copper and conductivity in artificial seawater.

PubMed

Herzog, Grégoire; Moujahid, Waleed; Twomey, Karen; Lyons, Conor; Ogurtsov, Vladimir I

2013-11-15

The fabrication and characterisation of microelectrochemical sensors for Cu(2+) and conductivity suitable for operation in the marine environment are presented. The impact of the designs on sensor performance and their adequacy to operate in real conditions are discussed. The sensors, tailored to voltammetric and impedimetric measurements, are fabricated on silicon using photolithographic and thin film deposition techniques. The impedimetric sensor is made of Pt interdigitated electrodes which are used for the measurement of conductivity. The voltammetric sensors are based on a three electrode electrochemical cell with on-chip Ag|AgCl reference and Pt counter and working electrodes, used for detection of copper by underpotential deposition-stripping voltammetry at microelectrode array. The sensors operated in the Cu(2+) concentrations ranging from 0.48 to 3.97 µM with a limit of detection of 0.115 μM. The impact of the temperature, the pH and the salinity of the artificial seawater on the sensitivity for Cu(2+) detection are also considered. Measurements of copper concentration and conductivity are validated using certified reference materials and standard solutions. PMID:24148368

4. Study of single-nucleotide polymorphisms by means of electrical conductance measurements

PubMed Central

Hihath, Joshua; Xu, Bingqian; Zhang, Peiming; Tao, Nongjian

2005-01-01

Understanding the complexities of DNA has been a hallmark of science for over a half century, and one of the important topics in DNA research is recognizing the occurrence of mutations in the base-stack. In this article, we present a study of SNPs by direct-contact electrical measurements to a single DNA duplex. We have used short, 11- and 12-bp dsDNA to investigate the change in conductance that occurs if a single base pair, a single base, or two separate bases in the stack are modified. All measurements are carried out in aqueous solution with the DNA chemically bound to the electrodes. These measurements demonstrate that the presence of a single base pair mismatch can be identified by the conductance of the molecule and can cause a change in the conductance of dsDNA by as much as an order of magnitude, depending on the specific details of the double helix and the single nucleotide polymorphism. PMID:16284253

5. Thermal conductivity measurements via time-domain thermoreflectance for the characterization of radiation induced damage

DOE PAGESBeta

Cheaito, Ramez; Gorham, Caroline S.; Carnegie Mellon Univ., Pittsburgh, PA; Misra, Amit; Hattar, Khalid; Hopkins, Patrick E.

2015-05-01

The progressive build up of displacement damage and fission products inside different systems and components of a nuclear reactor can lead to significant defect formation, degradation, and damage of the constituent materials. This structural modification can highly influence the thermal transport mechanisms and various mechanical properties of solids. In this paper we demonstrate the use of time-domain thermoreflectance (TDTR), a non-destructive method capable of measuring the thermal transport in material systems from nano to bulk scales, to study the effect of radiation damage and the subsequent changes in the thermal properties of materials. We use TDTR to show that displacementmore » damage from ion irradiation can significantly reduce the thermal conductivity of Optimized ZIRLO, a material used as fuel cladding in several current nuclear reactors. We find that the thermal conductivity of copper-niobium nanostructured multilayers does not change with helium ion irradiation doses of up to 1015 cm-2 and ion energy of 200 keV suggesting that these structures can be used and radiation tolerant materials in nuclear reactors. We compare the effect of ion doses and ion beam energies on the measured thermal conductivity of bulk silicon. Results demonstrate that TDTR thermal measurements can be used to quantify depth dependent damage.« less

6. Thermal conductivity measurements via time-domain thermoreflectance for the characterization of radiation induced damage

SciTech Connect

Cheaito, Ramez; Gorham, Caroline S.; Misra, Amit; Hattar, Khalid; Hopkins, Patrick E.

2015-05-01

The progressive build up of displacement damage and fission products inside different systems and components of a nuclear reactor can lead to significant defect formation, degradation, and damage of the constituent materials. This structural modification can highly influence the thermal transport mechanisms and various mechanical properties of solids. In this paper we demonstrate the use of time-domain thermoreflectance (TDTR), a non-destructive method capable of measuring the thermal transport in material systems from nano to bulk scales, to study the effect of radiation damage and the subsequent changes in the thermal properties of materials. We use TDTR to show that displacement damage from ion irradiation can significantly reduce the thermal conductivity of Optimized ZIRLO, a material used as fuel cladding in several current nuclear reactors. We find that the thermal conductivity of copper-niobium nanostructured multilayers does not change with helium ion irradiation doses of up to 1015 cm-2 and ion energy of 200 keV suggesting that these structures can be used and radiation tolerant materials in nuclear reactors. We compare the effect of ion doses and ion beam energies on the measured thermal conductivity of bulk silicon. Results demonstrate that TDTR thermal measurements can be used to quantify depth dependent damage.

7. Free-electron x-ray laser measurements of collisionally-damped plasmons in warm dense matter

Sperling, Philipp; Gamboa, Eliseo; Chung, Hyun; Omarbakiyeva, Yultuz; Reinholz, Heidi; Röpke, Gerd; Zastrau, Ulf; Fletcher, Luke; Lee, Hae-Ja; Glenzer, Siegfried

2015-06-01

In this talk, we will discuss the first measurement of strong collisions and dynamical screening effects affecting the electron-ion collisions and the electric conductivity of solid matter. We observed collisionally-damped plasmons in highly-spectrally resolved measurements of x-ray scattering from isochorically heated solid aluminum, which permits the first determination of the effects of dynamical screening and strong electron-ion collisions on the dynamic electrical conductivity. X-ray pulses from the seeded Linac Coherent Light Source delivering an average of 0 . 3 mJ of 8 keV x-ray photons in a 0 . 005 % bandwidth pulse, have been focused to micrometer diameter focal spots isochorically heating solid aluminum foils to temperatures up to 6 eV. The forward scattering spectra show plasmons that directly determine the temperature from detailed balance indicating a warm dense matter state. These experiments show a reduced electrical conductivity as well as a non-quadratic plasmon dispersion relation best described by taking into account electron-electron collisions as well as strong electron-ion collisions and dynamical screening effects that are beyond the Born approximation. These findings will affect measurements in the compressed density regime.

8. Flow Velocimetry for Weakly Conducting Electrolytes Based on High Resolution Lorentzforce Measurement

Ebert, R.; Vasilyan, S.; Wiederhold, A.

We demonstrate that a flow velocity measurement can be transformed into a non-invasive force measurement by metering the dragforce acting on a system of magnets that is arranged around a flow channel. This method is called Lorentzforce velocimetry and has been developed in the last years in our institute. It is a highly feasible principle for materials with large conductivity like liquid metals. To evolve this method for weakly conducting fluids like salt water or molten glass the dragforce measurement is the challenging bottleneck. Here forces of 10-8 and less of the weightforce of the magnet system have to be resolved in the rather noisy environment of the flow channel. In this paper different force measurement techniques get tested and compared. In the first setup the drag-force is acting on the magnets that are hanging as a pendulum with 0.5 m long wires on a mounting. Here the displacement in the range of a few μm can be detected with a laser interferometer and another optical positioning sensor. For the second setup the magnet system is attached to a state of the art electromagnetic force compensation balance. The balance is used in an unusual orientation: It is turned by 90 degrees to measure the horizontally acting Lorentzforce. Different ways of getting the correct force signal out of the two measurement setups will be presented and discussed. For generalization of the measurement principle the Lorentzforce is determined for different fluid profiles. In addition to that we have developed new systematic noise reduction methods to increase the resolution of both force measurement techniques by a factor of ten or larger which we will present here.

9. ENERGY-DISPERSIVE, X-RAY REFLECTIVITY DENSITY MEASUREMENTS OF POROUS SIO2 XEROGELS

EPA Science Inventory

X-ray reflectivity has been used to nondestructively measure the density of thin, porous, SiO2-based xerogels. Critical angle, defined by total external reflection, was measured for multiple x-ray energies to correct for sample misalignment error in me determination of the densit...

10. Gamma ray attenuation coefficient measurement for neutron-absorbent materials

2008-05-01

The compounds Na 2B 4O 7, H 3BO 3, CdCl 2 and NaCl and their solutions attenuate gamma rays in addition to neutron absorption. These compounds are widely used in the shielding of neutron sources, reactor control and neutron converters. Mass attenuation coefficients of gamma related to the four compounds aforementioned, in energies 662, 778.9, 867.38, 964.1, 1085.9, 1173, 1212.9, 1299.1,1332 and 1408 keV, have been determined by the γ rays transmission method in a good geometry setup; also, these coefficients were calculated by MCNP code. A comparison between experiments, simulations and Xcom code has shown that the study has potential application for determining the attenuation coefficient of various compound materials. Experiment and computation show that H 3BO 3 with the lowest average Z has the highest gamma ray attenuation coefficient among the aforementioned compounds.

11. X-ray reflectivity measurements of vacuum deposited thin films

SciTech Connect

Chason, M.; Chason, E.

1992-12-31

X-ray reflectivity using energy dispersive X-ray detection, a nondestructive probe of surface roughness over the region of {approximately} 1--50 {Angstrom}, has been used to investigate the characteristicsof vacuum deposited thin films. With a surface roughness sensitivity better than 1 {Angstrom} X-ray reflectivity is sensitive to interfaces between different materials for sample thicknesses up to approximately2000 {Angstrom} (depending on material density). We have investigated discrete Cr/Al deposits on quartz substrates and determined the surface roughness at the interfaces. We have also monitored the evolution ofthe Cr/Al interface following annealing. The experimental data is presented and discussed. The use of the technique for studying thin film deposits is addressed.

12. X-ray reflectivity measurements of vacuum deposited thin films

SciTech Connect

Chason, M. ); Chason, E. )

1992-01-01

X-ray reflectivity using energy dispersive X-ray detection, a nondestructive probe of surface roughness over the region of [approximately] 1--50 [Angstrom], has been used to investigate the characteristicsof vacuum deposited thin films. With a surface roughness sensitivity better than 1 [Angstrom] X-ray reflectivity is sensitive to interfaces between different materials for sample thicknesses up to approximately2000 [Angstrom] (depending on material density). We have investigated discrete Cr/Al deposits on quartz substrates and determined the surface roughness at the interfaces. We have also monitored the evolution ofthe Cr/Al interface following annealing. The experimental data is presented and discussed. The use of the technique for studying thin film deposits is addressed.

13. Kinetic coupling between electron and proton transfer in cytochrome c oxidase: simultaneous measurements of conductance and absorbance changes.

PubMed Central

Adelroth, P; Sigurdson, H; Hallén, S; Brzezinski, P

1996-01-01

Bovine heart cytochrome c oxidase is an electron-current driven proton pump. To investigate the mechanism by which this pump operates it is important to study individual electron- and proton-transfer reactions in the enzyme, and key reactions in which they are kinetically and thermodynamically coupled. In this work, we have simultaneously measured absorbance changes associated with electron-transfer reactions and conductance changes associated with protonation reactions following pulsed illumination of the photolabile complex of partly reduced bovine cytochrome c oxidase and carbon monoxide. Following CO dissociation, several kinetic phases in the absorbance changes were observed with time constants ranging from approximately 3 microseconds to several milliseconds, reflecting internal electron-transfer reactions within the enzyme. The data show that the rate of one of these electron-transfer reactions, from cytochrome a3 to a on a millisecond time scale, is controlled by a proton-transfer reaction. These results are discussed in terms of a model in which cytochrome a3 interacts electrostatically with a protonatable group, L, in the vicinity of the binuclear center, in equilibrium with the bulk through a proton-conducting pathway, which determines the rate of proton transfer (and indirectly also of electron transfer). The interaction energy of cytochrome a3 with L was determined independently from the pH dependence of the extent of the millisecond-electron transfer and the number of protons released, as determined from the conductance measurements. The magnitude of the interaction energy, 70 meV (1 eV = 1.602 x 10(-19) J), is consistent with a distance of 5-10 A between cytochrome a3 and L. Based on the recently determined high-resolution x-ray structures of bovine and a bacterial cytochrome c oxidase, possible candidates for L and a physiological role for L are discussed. PMID:8901574

14. Automated multi-point mini-disk infiltrometer measurements of unsaturated hydraulic conductivity

Klipa, Vladimir; Sacha, Jan; Snehota, Michal; Dohnal, Michal; Zumr, David; Tacheci, Pavel

2014-05-01

Unsaturated hydraulic conductivity function K(h) is one of hydraulic characteristics needed for numerical modeling of water flow and solute transport in the vadose zone. Tension infiltrometer is advantageous tool to conduct the measurement of unsaturated hydraulic conductivity in field under near saturated conditions. Manually operated minidisk infiltrometers are often used for performing infiltration experiments, but their disadvantage is that permanent attendance is needed during experiments. Therefore automatization of the tension infiltrometer is desirable. A new automated multi-disk tension infiltrometer has been designed at the Faculty of Civil Engineering, Czech Technical University in Prague to facilitate the measurements of near-saturated hydraulic conductivity. Infiltration experiment performed by device is simultaneously carried out by six tension mini-disk infiltrometer modules forming a fixed matrix as they are held by a lightweight aluminum frame. This setup is divided into the two groups of three infiltrometers. Each triplet of modules is controlled by Mariottes bottle. Therefore it is possible to conduct six simultaneous infiltration experiments at two different pressure heads. Amount of infiltrated water is registered via changes of buoyant force of vertical bar attached to the weighing sensor in each infiltrometer module and recorded automatically using datalogger. Cumulative infiltration and volumetric flux are calculated and displayed in real time. Near saturated hydraulic conductivity is determined from cumulative infiltration data using nonlinear optimization and improved procedure of Zhang. Device developed was to date tested on four experimental locations. Two sites were arable land (Nucice and Kopaninsky stream) and two located in headwater catchments (Sumava and Jizera Mountains). Soils at experimental sites were classified as Cambisols (empirical van Genuchten parameters α and n ranged from 0.007 to 0.043 cm-1 and from 1.13 to 1

15. Time-domain reflectometry: Simultaneous measurement of soil water content and electrical conductivity with a single probe

USGS Publications Warehouse

Dalton, F.N.; Herkelrath, W.N.; Rawlins, D.S.; Rhoades, J.D.

1984-01-01

Two parallel metallic rods were used as a wave guide to measure the dielectric constant and electrical conductivity of soils having different electrical conductivities but the same water content. Measurements showed that the two parameters were sufficiently independent to permit simultaneous determinations of water content and bulk electrical conductivity.

16. Atmospheric ionization and cosmic rays: studies and measurements before 1912

de Angelis, Alessandro

2014-01-01

The discovery of cosmic rays, a milestone in science, was based on the work by scientists in Europe and the New World and took place during a period characterized by nationalism and lack of communication. Many scientists that took part in this research a century ago were intrigued by the penetrating radiation and tried to understand the origin of it. Several important contributions to the discovery of the origin of cosmic rays have been forgotten; historical, political and personal facts might have contributed to their substantial disappearance from the history of science.

17. X-ray photoelectron spectroscopy and micro-Raman analysis of conductive RuO2 thin films

Bhaskar, S.; Dobal, P. S.; Majumder, S. B.; Katiyar, R. S.

2001-03-01

Ruthenium oxide (RuO2) was synthesized in thin film and powder forms using the solution chemistry technique. The oxide electrodes on Si substrates were characterized in terms of their structure, composition, stoichiometry, and conductivity. X-ray lattice parameter calculations and micro-Raman analysis revealed the rutile structure in the material. Both films and powders exhibited an unassigned Raman band at about 477 cm-1 in their Raman spectra. Performing peak frequency calculations for B2g and A1g modes of RuO2 using the rigid-ion model, which ruled out the possibility that this band originated from disorder induced symmetry, allowed silent mode. Based on the x-ray photoelectron spectroscopy (XPS) and temperature dependent Raman studies, this band was assigned to hydrated RuO2. XPS characterizations of our samples revealed minute surface contamination of oxygen and chlorine, probably due to the film preparation and high temperature deposition processes. Films with uniform microstructure, low surface roughness, and good electrical properties meet the requirements for serving as the bottom electrode for the ferroelectric capacitor.

18. Getting saturated hydraulic conductivity from surface Ground-Penetrating Radar measurements inside a ring infiltrometer

Leger, E.; Saintenoy, A.; Coquet, Y.

2013-12-01

fixed time steps, during an infiltration of 5 cm of water, inside a ring infiltrometer. We used the ring to demarcate the infiltration area, and to create reflexions at known depths. GPR reflexions coming from the wetting front as well as the buried edges of the cylinder were recorded. Modeling of the infiltration were made using SWMS-2D, GPR data of the infiltration were computed using GprMax suite programs. We generated 2D water content profiles associated with a saturated hydraulic conductivity value, at each experimental time step with SWMS-2D. Then we convert those profiles to 2D permittivity profiles using the Complex Refractive Index Method relation, to compute the reflexion time of the wetting front. We found the saturated hydraulic conductivity of soil by minimizing the differences between experimental and simulated data. Our retrieved saturated hydraulic conductivity from GPR data was compared to disk infiltrometer measurements.

19. Measurements of Separate Neutron and Gamma-Ray Coincidences with Liquid Scintillators and Digital PSD Technique

SciTech Connect

2007-10-01

A new technique is presented for the measurement of neutron and/or gamma-ray coincidences. Separate neutron neutron, neutron gamma-ray, gamma-ray neutron, and gamma-ray gamma-ray coincidences are acquired with liquid scintillation detectors and a digital pulse shape discrimination (PSD) technique based on standard charge integration method. The measurement technique allows for the collection of fast coincidences in a time window of the order of a few tens of nanoseconds between the coincident particles. The PSD allows for the acquisition of the coincidences in all particle combinations. The measurements are compared to results obtained with the MCNP-PoliMi code, which simulates neutron and gamma-ray coincidences from from a source on an event-by-event basis. This comparison leads to good qualitative agreement.

20. Thermal conductivity measurements of high and low thermal conductivity films using a scanning hot probe method in the 3ω mode and novel calibration strategies.

PubMed

Wilson, Adam A; Muñoz Rojo, Miguel; Abad, Begoña; Perez, Jaime Andrés; Maiz, Jon; Schomacker, Jason; Martín-Gonzalez, Marisol; Borca-Tasciuc, Diana-Andra; Borca-Tasciuc, Theodorian

2015-10-01

This work discusses measurement of thermal conductivity (k) of films using a scanning hot probe method in the 3ω mode and investigates the calibration of thermal contact parameters, specifically the thermal contact resistance (R(th)C) and thermal exchange radius (b) using reference samples with different thermal conductivities. R(th)C and b were found to have constant values (with b = 2.8 ± 0.3 μm and R(th)C = 44,927 ± 7820 K W(-1)) for samples with thermal conductivity values ranging from 0.36 W K(-1) m(-1) to 1.1 W K(-1) m(-1). An independent strategy for the calibration of contact parameters was developed and validated for samples in this range of thermal conductivity, using a reference sample with a previously measured Seebeck coefficient and thermal conductivity. The results were found to agree with the calibration performed using multiple samples of known thermal conductivity between 0.36 and 1.1 W K(-1) m(-1). However, for samples in the range between 16.2 W K(-1) m(-1) and 53.7 W K(-1) m(-1), calibration experiments showed the contact parameters to have considerably different values: R(th)C = 40,191 ± 1532 K W(-1) and b = 428 ± 24 nm. Finally, this work demonstrates that using these calibration procedures, measurements of both highly conductive and thermally insulating films on substrates can be performed, as the measured values obtained were within 1-20% (for low k) and 5-31% (for high k) of independent measurements and/or literature reports. Thermal conductivity results are presented for a SiGe film on a glass substrate, Te film on a glass substrate, polymer films (doped with Fe nano-particles and undoped) on a glass substrate, and Au film on a Si substrate. PMID:26335503

1. Course Manual for X-Ray Measurements (GS-462).

ERIC Educational Resources Information Center

Oregon State Univ., Corvallis. Dept. of General Science.

This is the second of three sequential course manuals for instructors in X-Ray science and engineering developed at Oregon State University. It consists of outlines for fourteen lectures and eight laboratory exercises with problems and two examinations. Also included is a list of references, equipment, and materials. The purposes, teaching aids,…

2. Fluid flow volume measurements using a capacitance/conductance probe system

NASA Technical Reports Server (NTRS)

Nguyen, T. X.; Arndt, G. D.; Carl, J. R.

1995-01-01

A probe system has been developed to measure the flow volume of a single fluid passing through an orifice or flow line. The system employs both capacitance and a conductance probe at the orifice, together with phase detection and data acquisition circuitry to measure flow volume and salinity under low or zero gravity conditions. A wide variety of frequencies can be used for the radio frequency (RF) signal source which is chosen primarily by the capacitance of the orifice probe and the fluid passing through the orifice. Rapid measurements are made using the reflected signal from the orifice probe to determine the 'instantaneous' permittivity of the fluid/gas mixture passing through. The 'instantaneous' measurements are integrated over time to determine flow volume. Analysis reveals that a narrow orifice helps to reduce non-linearities caused by differing flow rates. The geometry of 'deflectors' and 'directors' for the flowing fluid are important in obtaining linearity. Measured data shows that a volume measurement accuracy of approximately four percent can be consistently achieved. The prototype hardware system and associated software have been optimized and are available for further applications. The system has immediate application in low or zero gravity environments for measurements of urine or other liquid volumes.

3. Flat Field Anomalies in an X-ray CCD Camera Measured Using a Manson X-ray Source

SciTech Connect

M. J. Haugh and M. B. Schneider

2008-10-31

The Static X-ray Imager (SXI) is a diagnostic used at the National Ignition Facility (NIF) to measure the position of the X-rays produced by lasers hitting a gold foil target. The intensity distribution taken by the SXI camera during a NIF shot is used to determine how accurately NIF can aim laser beams. This is critical to proper NIF operation. Imagers are located at the top and the bottom of the NIF target chamber. The CCD chip is an X-ray sensitive silicon sensor, with a large format array (2k x 2k), 24 μm square pixels, and 15 μm thick. A multi-anode Manson X-ray source, operating up to 10kV and 10W, was used to characterize and calibrate the imagers. The output beam is heavily filtered to narrow the spectral beam width, giving a typical resolution E/ΔE≈10. The X-ray beam intensity was measured using an absolute photodiode that has accuracy better than 1% up to the Si K edge and better than 5% at higher energies. The X-ray beam provides full CCD illumination and is flat, within ±1% maximum to minimum. The spectral efficiency was measured at 10 energy bands ranging from 930 eV to 8470 eV. We observed an energy dependent pixel sensitivity variation that showed continuous change over a large portion of the CCD. The maximum sensitivity variation occurred at 8470 eV. The geometric pattern did not change at lower energies, but the maximum contrast decreased and was not observable below 4 keV. We were also able to observe debris, damage, and surface defects on the CCD chip. The Manson source is a powerful tool for characterizing the imaging errors of an X-ray CCD imager. These errors are quite different from those found in a visible CCD imager.

4. Measurements of the Conduction-Zone Length and Mass Ablation Rate to Study the Hydrodynamic Coupling in Cryogenic Direct-Drive Implosions on OMEGA

Michel, D. T.; Davis, A. K.; Goncharov, V. N.; Regan, S. P.; Sangster, T. C.; Epstein, R.; Hu, S. X.; Igumenshchev, I. V.; Meyerhofer, D. D.; Seka, W.; Froula, D. H.

2015-11-01

The ablation-front trajectory and the averaged mass ablation rate is measured in direct-drive cryogenic target implosions on the OMEGA Laser System by imaging the soft x rays emitted by the coronal plasma. The length of the conduction zone is determined by coupling x-ray and scattered-light measurements. These measurements are compared to hydrodynamic simulations to study the modeling of the hydrodynamic coupling for various beam and target radii. Reducing the beam focal-spot radius relative to the target radius is a method that is being studied to reduce cross-beam energy transfer and increase the hydrodynamic efficiency. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

5. Lunar magnetic field measurements, electrical conductivity calculations and thermal profile inferences

NASA Technical Reports Server (NTRS)

Colburn, D. S.

1971-01-01

Steady magnetic field measurements of magnitude 30 to 100 gamma on the lunar surface impose problems of interpretation when coupled with the nondetectability of a lunar field at 0.4 lunar radius altitude and the limb induced perturbations of the solar wind at the Explorer orbit. The lunar time-varying magnetic field clearly indicates the presence of eddy currents in the lunar interior and permits calculation of an electrical conductivity profile. The problem is complicated by the day-night asymmetry of the moon's electromagnetic environment, the possible presence of the transverse magnetic mode, and the variable wave directions of the driving function. The electrical conductivity is calculated to be low near the surface, rising to a peak of .006/ohm meter at 250 km, dropping steeply inwards to a value of about .00005/ohm meter, and then rising toward the interior. A transition at 250 km depth from a high conductivity to a low conductivity material is inferred, suggesting an olivine-like core at approximately 800 C, although other models are possible.

6. Measurement of local two-phase flow parameters of nanofluids using conductivity double-sensor probe

PubMed Central

2011-01-01

A two-phase flow experiment using air and water-based γ-Al2O3 nanofluid was conducted to observe the basic hydraulic phenomenon of nanofluids. The local two-phase flow parameters were measured with a conductivity double-sensor two-phase void meter. The void fraction, interfacial velocity, interfacial area concentration, and mean bubble diameter were evaluated, and all of those results using the nanofluid were compared with the corresponding results for pure water. The void fraction distribution was flattened in the nanofluid case more than it was in the pure water case. The higher interfacial area concentration resulted in a smaller mean bubble diameter in the case of the nanofluid. This was the first attempt to measure the local two-phase flow parameters of nanofluids using a conductivity double-sensor two-phase void meter. Throughout this experimental study, the differences in the internal two-phase flow structure of the nanofluid were identified. In addition, the heat transfer enhancement of the nanofluid can be resulted from the increase of the interfacial area concentration which means the available area of the heat and mass transfer. PMID:21711823

7. Electronic conductivity measurement of yttria-stabilized zirconia solid electrolytes by a transient technique

Zhang, Lei; Zhu, Liangzhu; Virkar, Anil V.

2016-01-01

A new oxygen permeation technique is developed to measure the electronic conductivity of yttria-stabilized zirconia (YSZ). The permeation cell is a YSZ disc with an embedded Pt probe and a cavity at the center. Two porous platinum electrodes are applied on the disc surfaces. By applying a small DC bias (0.03 V) across one surface electrode and the embedded probe, oxygen is pumped into the YSZ disc and stored in the cavity. In steady state, a stable Nernst potential is developed between the cavity and the outer surfaces. The Nernst voltage is very close to the applied voltage since YSZ is essentially an ionic conductor. When the DC bias is removed, oxygen permeates out of the cavity leading to a decay of the Nernst potential. Electronic conductivity of YSZ corresponding to the ambient oxygen pressure (∼0.21 atm) is determined by analyzing the time dependence of the decay of Nernst potential. The measured electronic conductivity is in good agreement with values reported in the literature.

8. Thermal resistance technique for measuring the thermal conductivity of thin microporous membranes

García-Payo, M. C.; Izquierdo-Gil, M. A.

2004-11-01

The thermal resistance technique for measurement of the thermal conductivity of microporous thin membranes is described. A modified and enhanced Lees' disc apparatus was used. Several samples of membranes were held between a hot copper plate and a cold copper base, and the temperature differences between them were measured using thermocouples under steady-state conditions. The accuracy and reliability of the results were checked by means of a comparative test on a standard bad conductor. A dependence of the thermal resistance on the thickness of the samples was observed. The thermal conductivity of the membrane was deduced from a linear fit of the thermal resistance versus the number of membranes. Better results were obtained when the air layer effect was considered in the linear fit. Several models found in the literature and based on empirical correlations or on theoretical structure models (such as Maxwell's, Fricke's or Misra's models) were tested in order to calculate the effective thermal conductivity of the membrane. These values were compared with the experimental ones and they showed a better agreement than the parallel model commonly used in the literature for the membranes studied in this work.

9. A flash heating method for measuring thermal conductivity at high pressure and temperature: Application to Pt

McWilliams, R. Stewart; Konôpková, Zuzana; Goncharov, Alexander F.

2015-10-01

The transport properties of matter at high pressure and temperature are critical components in planetary interior models, yet are challenging to measure or predict at relevant conditions. Using a novel flash-heating method for in-situ high-temperature and high-pressure thermal conductivity measurement, we study the transport properties of platinum to 55 GPa and 2300 K. Experimental data reveal a simple high-pressure and high-temperature behavior of the thermal conductivity that is linearly dependent on both pressure and temperature. The corresponding electrical resistivity evaluated through the Wiedemann-Franz-Lorenz law is nearly constant along the melting curve, experimentally confirming the prediction of Stacey for an ideal metal. This study together with prior first-principles predictions of transport properties in Al and Fe at extreme conditions suggests a broad applicability of Stacey's law to diverse metals, supporting a limit on the thermal conductivity of iron at the conditions of Earth's outer core of 90 W/mK or less.

10. Measurement of local two-phase flow parameters of nanofluids using conductivity double-sensor probe

Park, Yu Sun; Chang, Soon Heung

2011-12-01

A two-phase flow experiment using air and water-based γ-Al2O3 nanofluid was conducted to observe the basic hydraulic phenomenon of nanofluids. The local two-phase flow parameters were measured with a conductivity double-sensor two-phase void meter. The void fraction, interfacial velocity, interfacial area concentration, and mean bubble diameter were evaluated, and all of those results using the nanofluid were compared with the corresponding results for pure water. The void fraction distribution was flattened in the nanofluid case more than it was in the pure water case. The higher interfacial area concentration resulted in a smaller mean bubble diameter in the case of the nanofluid. This was the first attempt to measure the local two-phase flow parameters of nanofluids using a conductivity double-sensor two-phase void meter. Throughout this experimental study, the differences in the internal two-phase flow structure of the nanofluid were identified. In addition, the heat transfer enhancement of the nanofluid can be resulted from the increase of the interfacial area concentration which means the available area of the heat and mass transfer.

11. Graphene Nanopore Support System for Simultaneous High-Resolution AFM Imaging and Conductance Measurements

PubMed Central

2015-01-01

Accurately defining the nanoporous structure and sensing the ionic flow across nanoscale pores in thin films and membranes has a wide range of applications, including characterization of biological ion channels and receptors, DNA sequencing, molecule separation by nanoparticle films, sensing by block co-polymers films, and catalysis through metal–organic frameworks. Ionic conductance through nanopores is often regulated by their 3D structures, a relationship that can be accurately determined only by their simultaneous measurements. However, defining their structure–function relationships directly by any existing techniques is still not possible. Atomic force microscopy (AFM) can image the structures of these pores at high resolution in an aqueous environment, and electrophysiological techniques can measure ion flow through individual nanoscale pores. Combining these techniques is limited by the lack of nanoscale interfaces. We have designed a graphene-based single-nanopore support (∼5 nm thick with ∼20 nm pore diameter) and have integrated AFM imaging and ionic conductance recording using our newly designed double-chamber recording system to study an overlaid thin film. The functionality of this integrated system is demonstrated by electrical recording (<10 pS conductance) of suspended lipid bilayers spanning a nanopore and simultaneous AFM imaging of the bilayer. PMID:24581087

12. High temperature thermal conductivity measurements on lanthanum sulfides using the flash method

NASA Technical Reports Server (NTRS)

Vandersande, J. W.; Wood, C.; Zoltan, A.; Whittenberger, D.

1988-01-01

In the past, high temperature specific heat and hence thermal conductivity measurements, using the flash method have not been very accurate. This is due to the difficulty of exactly determining the amount of heat deposited on the front face of a sample during each flash. This problem has now been solved by sputtering a thin layer of graphite on the standard reference and test samples. Data taken shows that the amount of heat deposited can now be determined to within about 2 percent resulting in more accurate thermal conductivity data. The results of measurements on several lanthanum sulfides with stoichiometries between LaS(1.35) and LaS(1.48) are reported and show a minimum in the lattice thermal conductivity at a composition of around LaS(1.41). This is believed to be due to the scattering of low-frequency phonons by large defects, i.e., second phase material (beta-phase) and pores.

13. A high sensitivity ultralow temperature RF conductance and noise measurement setup.

PubMed

Parmentier, F D; Mahé, A; Denis, A; Berroir, J-M; Glattli, D C; Plaçais, B; Fève, G

2011-01-01

We report on the realization of a high sensitivity RF noise measurement scheme to study small current fluctuations of mesoscopic systems at milli-Kelvin temperatures. The setup relies on the combination of an interferometric amplification scheme and a quarter-wave impedance transformer, allowing the measurement of noise power spectral densities with gigahertz bandwidth up to five orders of magnitude below the amplifier noise floor. We simultaneously measure the high frequency conductance of the sample by derivating a portion of the signal to a microwave homodyne detection. We describe the principle of the setup, as well as its implementation and calibration. Finally, we show that our setup allows to fully characterize a subnanosecond on-demand single electron source. More generally, its sensitivity and bandwidth make it suitable for applications manipulating single charges at GHz frequencies. PMID:21280842

14. UNSATURATED FLOW IN A CENTRIFUGAL FIELD: MEASUREMENT OF HYDRAULIC CONDUCTIVITY AND TESTING OF DARCY'S LAW.

USGS Publications Warehouse

Nimmo, J.R.; Rubin, J.; Hammermeister, D.P.

1987-01-01

A method has been developed to establish steady flow of water in unsaturated soil sample spinning in a centrifuge. Theoretical analysis predicts moisture conditions in the sample that depend strongly on soil type and certain operating parameter. For Oakley sand, measurements of flux, water content, and matric potential during and after centrifugation verify that steady state flow can be achieved. Experiments have confirmed the theoretical prediction of a nearly uniform moisture distribution for this medium and have demonstrated that the flow can be effectively one-dimensional. The method was used for steady state measurements of hydraulic conductivity K for relatively dry soil, giving values at low as 7. 6 multiplied by 10** minus **1**1 m/s with data obtained in a few hours. Darcy's law was tested by measuring K for different centrifugal driving forces but with the same water content.

15. Measurement of the high-frequency complex permittivity and conductivity of magnetic fluids

Fannin, P. C.; Charles, S. W.; Vincent, D.; Giannitsis, A. T.

2002-11-01

Measurements of the permittivity, ɛ( ω)= ɛ'( ω)-i ɛ″( ω), and conductivity, σ( ω)= ωɛ0ɛ″( ω), of two ferrofluid samples of ferrite particles in a hydrocarbon carrier, isopar M, over the frequency range 0.1-6 GHz are presented. It is shown that the sample with the highest concentration of particles has the highest permittivity and by means of profile fitting it is demonstrated, for the first time, that σ( ω) has a Debye-type profile. The frequency limitation of the used measurement technique is highlighted and a possible alternative technique capable of measuring in the 20-30 GHz region is presented.

16. G-300: The first French Getaway Special microgravity measurements of fluid thermal conductivity

NASA Technical Reports Server (NTRS)

Perron, J. C.; Chretien, P.; Garnier, C.; Lecaude, N.

1987-01-01

Thermal conductivity measurements on liquids are difficult to perform on Earth because of thermal motions due to convection. In microgravity, the convection due to buoyancy is evanescent, and a strong reduction of Rayleigh and Nusselt numbers can be expected. Three low viscosity liquids are selected to carry out the measurements; distilled water (standard) and two silicone oils. A modified hot plate method with a simplified guard ring is used; the reduction of convective motions permitted the use in the experimental cells of larger interplate distances and/or temperature differences than in Earth measurements, improving the accuracy. Comparisons between Earth and orbit results may help to understand the convection occurrence in the cells. Thermal, vibrational, and EMI tests have proved that the design satisfies the NASA requirements.

17. A high sensitivity ultralow temperature RF conductance and noise measurement setup

SciTech Connect

Parmentier, F. D.; Mahe, A.; Denis, A.; Berroir, J.-M.; Glattli, D. C.; Placais, B.; Feve, G.

2011-01-15

We report on the realization of a high sensitivity RF noise measurement scheme to study small current fluctuations of mesoscopic systems at milli-Kelvin temperatures. The setup relies on the combination of an interferometric amplification scheme and a quarter-wave impedance transformer, allowing the measurement of noise power spectral densities with gigahertz bandwidth up to five orders of magnitude below the amplifier noise floor. We simultaneously measure the high frequency conductance of the sample by derivating a portion of the signal to a microwave homodyne detection. We describe the principle of the setup, as well as its implementation and calibration. Finally, we show that our setup allows to fully characterize a subnanosecond on-demand single electron source. More generally, its sensitivity and bandwidth make it suitable for applications manipulating single charges at GHz frequencies.

18. Critical Review of Industrial Techniques for Thermal-Conductivity Measurements of Thermal Insulation Materials

2015-07-01

This paper presents a critical review of current industrial techniques and instruments to measure the thermal conductivity of thermal insulation materials, especially those insulations that can operate at temperatures above and up to . These materials generally are of a porous nature. The measuring instruments dealt with here are selected based on their maximum working temperature that should be higher than at least . These instruments are special types of the guarded hot-plate apparatus, the guarded heat-flow meter, the transient hot-wire and hot-plane instruments as well as the laser/xenon flash devices. All technical characteristics listed are quoted from the generally accessible information of the relevant manufacturers. The paper includes rankings of the instruments according to their standard retail price, the maximum sample size, and maximum working temperature, as well as the minimum in their measurement range.

19. Flash X-Ray (FXR) Accelerator Optimization Electronic Time-Resolved Measurement of X-Ray Source Size

SciTech Connect

Jacob, J; Ong, M; Wargo, P

2005-07-21

Lawrence Livermore National Laboratory (LLNL) is currently investigating various approaches to minimize the x-ray source size on the Flash X-Ray (FXR) linear induction accelerator in order to improve x-ray flux and increase resolution for hydrodynamic radiography experiments. In order to effectively gauge improvements to final x-ray source size, a fast, robust, and accurate system for measuring the spot size is required. Timely feedback on x-ray source size allows new and improved accelerator tunes to be deployed and optimized within the limited run-time constraints of a production facility with a busy experimental schedule; in addition, time-resolved measurement capability allows the investigation of not only the time-averaged source size, but also the evolution of the source size, centroid position, and x-ray dose throughout the 70 ns beam pulse. Combined with time-resolved measurements of electron beam parameters such as emittance, energy, and current, key limiting factors can be identified, modeled, and optimized for the best possible spot size. Roll-bar techniques are a widely used method for x-ray source size measurement, and have been the method of choice at FXR for many years. A thick bar of tungsten or other dense metal with a sharp edge is inserted into the path of the x-ray beam so as to heavily attenuate the lower half of the beam, resulting in a half-light, half-dark image as seen downstream of the roll-bar; by measuring the width of the transition from light to dark across the edge of the roll-bar, the source size can be deduced. For many years, film has been the imaging medium of choice for roll-bar measurements thanks to its high resolution, linear response, and excellent contrast ratio. Film measurements, however, are fairly cumbersome and require considerable setup and analysis time; moreover, with the continuing trend towards all-electronic measurement systems, film is becoming increasingly difficult and expensive to procure. Here, we shall

20. Measurements of the cosmic-ray Be/B ratio and the age of cosmic rays

NASA Technical Reports Server (NTRS)

Brown, J. W.; Stone, E. C.; Vogt, R. E.

1974-01-01

The ratio Be/B depends on whether the confinement time of cosmic rays in the Galaxy is long or short compared to the radioactive half-life of Be-10. We report observations of this ratio which were obtained with a dE/dx-Cerenkov detector launched into a polar orbit on OGO-6 as part of the Caltech Solar and Galactic Cosmic Ray Experiment. Be/B ratios were determined for various rigidity thresholds up to 15 GV. We find no statistically significant rigidity dependence of the ratio, which is 0.41 plus or minus 0.02 when averaged over all observed cutoffs. Additional calculations suggest that if the present fragmentation parameters are correct, then the lifetime of cosmic rays in the Galaxy is less then 10 m.y.
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