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Apparent Linear Attenuation Coefficients in Phase Contrast X-Ray Tomography
Yan, Aimin; Wu, Xizeng
In the inline phase contrast x-ray tomography the reconstructed apparent linear attenuation coefficient values may be greatly larger than sampleÆs linear attenuation coefficients or even be negative. In this work we present a general formula to quantitatively relate the apparent linear attenuation coefficient values in cone-beam phase contrast tomography to sampleÆs linear attenuation coefficients and refractive indices. This formula overcomes the gross inaccuracy of the existing formula in the literature in analyzing high-resolution phase contrast tomography, and it will be useful for correctly interpreting and quantifying the apparent linear attenuation coefficients in cone-beam x-ray phase contrast tomography. PMID:21691420
Uranium soft x-ray total attenuation coefficients
Del Grande, N.K.; Oliver, A.J.
Uranium total attenuation coefficients were measured continuously from 0.84 to 6.0 keV and at selected higher energies using a vacuum single crystal diffractometer and flow-proportional counter. Statistical fluctuations ranged from 0.5% to 2%. The overall accuracy was 3%. Prominent structure was measured within 20 eV of the M/sub 5/ (3.552 keV) and M/sub 4/ (3.728 keV) edges. Jump ratios were determined from log-log polynomial fits to data at energies apart from the near-edge regions. These data were compared with calculations based on a relativistic HFS central potential model and with previously tabulated data.
X-Ray Attenuation Coefficients from 13 to 80 Mev for Hydrogen, Carbon, Water, and Aluminum
J. M. Wyckoff; H. W. Koch
The x-ray attenuation coefficients for hydrogen, carbon, water, and aluminum have been measured in the energy range from 13 to 80 Mev by placing varying lengths of attenuators in a 90-Mev bremsstrahlung beam in a good geometry experiment using a large sodium-iodide total-absorption spectrometer as the detector. In the hydrogen case, a difference method employing cyclohexane (C6H12) and graphite was
New consistency tests for high-accuracy measurements of X-ray mass attenuation coefficients by the X-ray extended-range technique
Chantler, C.T.; Islam, M.T.; Rae, N.A.; Tran, C.Q.; Glover, J.L.; Barnea, Z. (La Trobe); (Melbourne)
An extension of the X-ray extended-range technique is described for measuring X-ray mass attenuation coefficients by introducing absolute measurement of a number of foils - the multiple independent foil technique. Illustrating the technique with the results of measurements for gold in the 38-50 keV energy range, it is shown that its use enables selection of the most uniform and well defined of available foils, leading to more accurate measurements; it allows one to test the consistency of independently measured absolute values of the mass attenuation coefficient with those obtained by the thickness transfer method; and it tests the linearity of the response of the counter and counting chain throughout the range of X-ray intensities encountered in a given experiment. In light of the results for gold, the strategy to be ideally employed in measuring absolute X-ray mass attenuation coefficients, X-ray absorption fine structure and related quantities is discussed.
Beam hardening: Analytical considerations of the effective attenuation coefficient of x-ray tomography
Alles, J.; Mudde, R. F. [Kramers Laboratorium voor Fysische Technology, Department of Multi-Scale Physics, Delft University of Technology, Pr. Bernhardlaan 6, 2628 Delft (Netherlands)
Polychromatic x-ray beams traveling though material are prone to beam hardening, i.e., the high energy part of the incident spectrum gets over represented when traveling farther into the material. This study discusses the concept of a mean attenuation coefficient in a formal way. The total energy fluence is one-to-one related to the traveled distance in case of a polychromatic beam moving through a given, inhomogeneous material. On the basis of this one-to-one relation, it is useful to define a mean attenuation coefficient and study its decrease with depth. Our results are based on a novel parametrization of the energy dependence of the attenuation coefficient that allows for closed form evaluation of certain spectral integrals. This approach underpins the ad hoc semianalytical expressions given in the literature. An analytical model for the average attenuation coefficient is proposed that uses a simple fit of the attenuation coefficient as a function of the photon energy as input. It is shown that a simple extension of this model gives a rather good description of beam hardening for x-rays traveling through water.
Measurement of mass attenuation coefficients of biological materials by energy dispersive X-ray fluorescence spectrometry
N. Ekinci; N. Astam
The mass attenuation coefficients for cornea taken from keratitis patient and soft contact lens (-1.75, -3.75, -4 dioptres), leiomyomata uteri and uterus were measured in the X-ray energy (5.9keV) using a SiLi detector and Fe55 annular source. Full details of the experimental method, experimental set up, the procedure of sample preparation and the results within estimated error are presented. Energy
Measurement of mass attenuation coefficients and effective atomic numbers for MgB 2 superconductor using X-ray energies
H. Balta?; ?. Ūelik; U. Ūevik; E. Yanmaz
The powder and bulk MgB2 superconductors sintered in different Ar gas pressures were investigated using X-ray diffraction patterns, mass density and mass attenuation coefficient measurements. During the sintering process, 2, 4, 6, 8 and 10bar argon pressures were used to minimize the evaporation of Mg from the compound. Mass attenuation coefficients (?\\/?) of powder and bulk samples were determined by
Determination of the mass attenuation coefficients for X-ray fluorescence measurements correction by the Rayleigh to Compton scattering ratio
NASA Astrophysics Data System (ADS)
Conti, C. C.; Anjos, M. J.; Salgado, C. M.
X-ray fluorescence technique plays an important role in nondestructive analysis nowadays. The development of equipment, including portable ones, enables a wide assortment of possibilities for analysis of stable elements, even in trace concentrations. Nevertheless, despite of the advantages, one important drawback is radiation self-attenuation in the sample being measured, which needs to be considered in the calculation for the proper determination of elemental concentration. The mass attenuation coefficient can be determined by transmission measurement, but, in this case, the sample must be in slab shape geometry and demands two different setups and measurements. The Rayleigh to Compton scattering ratio, determined from the X-ray fluorescence spectrum, provides a link to the mass attenuation coefficient by means of a polynomial type equation. This work presents a way to construct a Rayleigh to Compton scattering ratio versus mass attenuation coefficient curve by using the MCNP5 Monte Carlo computer code. The comparison between the calculated and literature values of the mass attenuation coefficient for some known samples showed to be within 15%. This calculation procedure is available on-line at www.macx.net.br.
Measurement of X-ray mass attenuation coefficients in biological and geological samples in the energy range of 7-12keV.
Trunova, Valentina; Sidorina, Anna; Kriventsov, Vladimir
Information about X-ray mass attenuation coefficients in different materials is necessary for accurate X-ray fluorescent analysis. The X-ray mass attenuation coefficients for energy of 7-12keV were measured in biological (Mussel and Oyster tissues, blood, hair, liver, and Cabbage leaves) and geological (Baikal sludge, soil, and Alaskite granite) samples. The measurements were carried out at the EXAFS Station of Siberian Synchrotron Radiation Center (VEPP-3). Obtained experimental mass attenuation coefficients were compared with theoretical values calculated for some samples. PMID:25464176
Measurements of the X-ray linear attenuation coefficient for low atomic number materials at energies 32¢66 and 140 keV
S. M. Midgley
The X-ray linear attenuation coefficient was measured for materials containing elements hydrogen to calcium. Characteristic X-rays with energies 32¢66keV were produced by X-ray fluorescence using a secondary target system, and 140keV gamma rays were obtained from an unsealed 99mTc source. The photon beams were highly collimated and recorded using energy dispersive detection. A high-purity germanium detector was utilised to distinguish
Measurements of the X-ray linear attenuation coefficient for low atomic number materials at energies 32-66 and 140keV
S. M. Midgley
The X-ray linear attenuation coefficient was measured for materials containing elements hydrogen to calcium. Characteristic X-rays with energies 32-66keV were produced by X-ray fluorescence using a secondary target system, and 140keV gamma rays were obtained from an unsealed 99mTc source. The photon beams were highly collimated and recorded using energy dispersive detection. A high-purity germanium detector was utilised to distinguish
Measurement of the x-ray mass attenuation coefficients of gold in the 38?50-keV energy range
Islam, M.T.; Rae, N.A.; Glover, J.L.; Barnea, Z.; de Jonge, M.D.; Tran, C.Q.; Wang, J.; Chantler, C.T. (Melbourne)
We used synchrotron x rays to measure the x-ray mass attenuation coefficients of gold at nine energies from 38 to 50 keV with accuracies of 0.1%. Our results are much more accurate than previous measurements in this energy range. A comparison of our measurements with calculated mass attenuation coefficients shows that our measurements fall almost exactly midway between the XCOM and FFAST calculated theoretical values, which differ from one another in this energy region by about 4%, even though the range includes no absorption edge. The consistency and accuracy of these measurements open the way to investigations of the x-ray attenuation in the region of the L absorption edge of gold.
X-Ray Form Factor, Attenuation and Scattering Tables
National Institute of Standards and Technology Data Gateway
SRD 66 X-Ray Form Factor, Attenuation and Scattering Tables (Web, free access)ĀĀ This database collects tables and graphs of the form factors, the photoabsorption cross section, and the total attenuation coefficient for any element (Z <= 92).
Measurement of x-ray attenuation coefficients for elements in the range 79 less than or equal to Z less than or equal to 92
N. S. Saleh; M. A. Sharif; K. A. Al-Saleh
A method for measuring the X-ray attenuation coefficients for elements with 79 less than or equal to Z less than or equal to 92 at the excitation energy of 121.9 keV (Gamma-rays emitted by Co-57 radioisotope source) is described. The accuracy is greatly improved by intensity ratio measurements of infinitely thin and thick targets; thus the uncertainties in the fundamental
Chemical effects on K?/K? X-ray intensity ratios of Mo, Ag, Cd, Ba, La, Ce compounds and total mass attenuation coefficients of Fe and Cu
NASA Astrophysics Data System (ADS)
S÷g³t, ų.; Seven, S.; Baydas, E.; B³y³kkasap, E.; K³ń³k÷nder, A.
The K?/K? intensity ratios for pure Mo, Ag, Cd, Ba, La and Ce elements and for some of their compounds were investigated. The vacancies in the K shell were created by 59.5-keV ?-rays from a heavily filtered 241Am radioactive source. K X-rays were measured using a Si(Li) detector with a resolution of 155 eV at 5.9 keV. We observed chemical effects on K?/K? intensity ratios of Mo, Ag, Cd, Ba, La and Ce compounds. Detailed interpretation of data obtained from X-ray transmission measurements usually depends on the assumption that the contribution of each element is additive. This assumption yields the mixture rule for X-ray attenuation coefficients which is valid if molecular and chemical effects are negligible. We measured the total mass attenuation coefficients of Fe and Cu in various compounds. Self-absorption corrections were carried out on data for ligands in the different compounds. Our values were compared with the theoretical values for pure elements.
Tables of X-ray mass attenuation coefficients and mass energy-absorption coefficients 1 keV to 20 MeV for elements Z=1 to 92 and 48 additional substances of dosimetric interest
J. H. Hubbell; Stephen M Seltzer
Tables and graphs of the photon mass attenuation coefficient mu\\/rho and the mass energy-absorption coefficient mu(en)\\/rho are presented for all of the elements Z=1 to 92, and for 48 compounds and mixtures of radiological interest. The tables cover energies of the photon (x ray, gamma ray, bremsstrahlung) from 1 keV to 20 MeV. The mu\\/rho values are taken from the
Measurement of the x-ray mass attenuation coefficient and determination of the imaginary component of the atomic form factor of tin over the energy range of 29-60 keV
Martin D. de Jonge; Chanh Q. Tran; Christopher T. Chantler; Zwi Barnea; Bipin B. Dhal; David Paterson; Elliot P. Kanter; Stephen H. Southworth; Linda Young; Mark A. Beno; Jennifer A. Linton; Guy Jennings
We use the x-ray extended-range technique (XERT) [C. T. Chantler et al., Phys. Rev. A 64, 062506 (2001)] to measure the mass attenuation coefficients of tin in the x-ray energy range of 29-60 keV to 0.04-3 % accuracy, and typically in the range 0.1-0.2 %. Measurements made over an extended range of the measurement parameter space are critically examined to
Measurement of the x-ray mass attenuation coefficient and determination of the imaginary component of the atomic form factor of tin over the energy range of 29-60keV
Martin D. de Jonge; Chanh Q. Tran; Christopher T. Chantler; Zwi Barnea; Bipin B. Dhal; David Paterson; Elliot P. Kanter; Stephen H. Southworth; Linda Young; Mark A. Beno; Jennifer A. Linton; Guy Jennings
We use the x-ray extended-range technique (XERT) [C. T. Chantler , Phys. Rev. A 64, 062506 (2001)] to measure the mass attenuation coefficients of tin in the x-ray energy range of 29-60keV to 0.04-3% accuracy, and typically in the range 0.1-0.2% . Measurements made over an extended range of the measurement parameter space are critically examined to identify, quantify, and
Measurement of the x-ray mass attenuation coefficient and determination of the imaginary component of the atomic form-factor of tin over the energy range of 29 keV-60 keV.
de Jonge, M. D.; Tran, C. Q.; Chantler, C. T.; Barnea, Z.; Dhal, B. P.; Paterson, D.; Kanter, E. P.; Southworth, S. H.; Young, L.; Beno, M. A.; Linton, J. A.; Jennings, G.; Univ. of Melbourne; Australian Synchrotron Project
We use the x-ray extended-range technique (XERT) [C. T. Chantler et al., Phys. Rev. A 64, 062506 (2001)] to measure the mass attenuation coefficients of tin in the x-ray energy range of 29-60 keV to 0.04-3 % accuracy, and typically in the range 0.1-0.2 %. Measurements made over an extended range of the measurement parameter space are critically examined to identify, quantify, and correct a number of potential experimental systematic errors. These results represent the most extensive experimental data set for tin and include absolute mass attenuation coefficients in the regions of x-ray absorption fine structure, extended x-ray absorption fine structure, and x-ray absorption near-edge structure. The imaginary component of the atomic form factor f{sub 2} is derived from the photoelectric absorption after subtracting calculated Rayleigh and Compton scattering cross sections from the total attenuation. Comparison of the result with tabulations of calculated photoelectric absorption coefficients indicates that differences of 1-2 % persist between calculated and observed values.
Measurement of the x-ray mass attenuation coefficient and determination of the imaginary component of the atomic form factor of tin over the energy range of 29-60 keV
Jonge, Martin D. de; Tran, Chanh Q.; Chantler, Christopher T.; Barnea, Zwi; Dhal, Bipin B.; Paterson, David; Kanter, Elliot P.; Southworth, Stephen H.; Young, Linda; Beno, Mark A.; Linton, Jennifer A.; Jennings, Guy [X-Ray Operations and Research, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States); School of Physics, University of Melbourne, Victoria 3010 (Australia); Australian Synchrotron Project, Major Projects Victoria, 800 Blackburn Road, Clayton, Victoria 3168 (Australia); Chemistry Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States); BESSRC-CAT, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States)
We use the x-ray extended-range technique (XERT) [C. T. Chantler et al., Phys. Rev. A 64, 062506 (2001)] to measure the mass attenuation coefficients of tin in the x-ray energy range of 29-60 keV to 0.04-3 % accuracy, and typically in the range 0.1-0.2 %. Measurements made over an extended range of the measurement parameter space are critically examined to identify, quantify, and correct a number of potential experimental systematic errors. These results represent the most extensive experimental data set for tin and include absolute mass attenuation coefficients in the regions of x-ray absorption fine structure, extended x-ray absorption fine structure, and x-ray absorption near-edge structure. The imaginary component of the atomic form factor f{sub 2} is derived from the photoelectric absorption after subtracting calculated Rayleigh and Compton scattering cross sections from the total attenuation. Comparison of the result with tabulations of calculated photoelectric absorption coefficients indicates that differences of 1-2 % persist between calculated and observed values.
X-Ray Attenuation and Absorption for Materials of Dosimetric Interest
National Institute of Standards and Technology Data Gateway
SRD 126 X-Ray Attenuation and Absorption for Materials of Dosimetric Interest (Web, free access)ĀĀ Tables and graphs of the photon mass attenuation coefficient and the mass energy-absorption coefficient are presented for all of the elements Z = 1 to 92, and for 48 compounds and mixtures of radiological interest. The tables cover energies of the photon (x-ray, gamma ray, bremsstrahlung) from 1 keV to 20 MeV.
X-ray attenuation coefficients of Fe compounds in the Kedge region at different energies and the validity of the mixture rule
U. Turgut; E. Buyukkasap; O. ?im?ek; M. Ertugrul
The total mass attenuation coefficients for element Fe and compounds FeF3, Fe2O3, FeCl2Ę4H2O, FeCl32NH4ClĘH2O were measured at different energies between 4.508¢17.443keV range by using secondary excitation method. Ti, V, Cr, Ni, Cu, Zn, As, Se, Br, Rb, Sr, Y, Zr, Nb, Mo were chosen as secondary exciter. 59.5keV gamma rays emitted from an 241Am annular source were used to excite
X-ray attenuation properties of stainless steel (u)
Wang, Lily L [Los Alamos National Laboratory; Berry, Phillip C [Los Alamos National Laboratory
Stainless steel vessels are used to enclose solid materials for studying x-ray radiolysis that involves gas release from the materials. Commercially available stainless steel components are easily adapted to form a static or a dynamic condition to monitor the gas evolved from the solid materials during and after the x-ray irradiation. Experimental data published on the x-ray attenuation properties of stainless steel, however, are very scarce, especially over a wide range of x-ray energies. The objective of this work was to obtain experimental data that will be used to determine how a poly-energetic x-ray beam is attenuated by the stainless steel container wall. The data will also be used in conjunction with MCNP (Monte Carlos Nuclear Particle) modeling to develop an accurate method for determining energy absorbed in known solid samples contained in stainless steel vessels. In this study, experiments to measure the attenuation properties of stainless steel were performed for a range of bremsstrahlung x-ray beams with a maximum energy ranging from 150 keV to 10 MeV. Bremsstrahlung x-ray beams of these energies are commonly used in radiography of engineering and weapon components. The weapon surveillance community has a great interest in understanding how the x-rays in radiography affect short-term and long-term properties of weapon materials.
X-Ray attenuation coefficients at different energies and the validity of the mixture rule for compounds around the absorption edge
▄. Turgut; ų ?im?ek; E. B³y³kkasap; M. Ertu?rul
The total mass attenuation coefficients for the elements Co, Mn and Co2O3, compounds CoCl2.6H2O, CoSO4, CoSO4.7H2O, MnCO3, KMnO4, MnCl2.2H2O, and MnCl2.4H2O were measured at different energies between 4.508 and 11.210 keV using a secondary excitation method. Ti, Co, Ni, Cu, Zn, As, Se were chosen as secondary exciter. Gamma rays (59.5 keV) emitted from an 241Am annular source were used
Novel x-ray attenuation mechanism: Role of interatomic distance
Poelzing, Steven; Smoot, Adam F.; Veeraraghavan, Rengasayee [Nora Eccles Harrison Cardiovascular Research and Training Institute and Bioengineering, University of Utah, 95 South 2000 East, Salt Lake City, Utah 84112 (United States)
Little progress has been made over the last 30 years for improving attenuation by x-ray contrast agents, in part because the mechanisms of x-ray attenuation are thought to be well understood. We hypothesized that x-ray absorbance can be modulated by altering the interatomic spacing between K-edge attenuating atoms. Iodomethane, diiodomethane, 2,6-diiodo-4-nitroanaline, and diiodobenzene isomers were dissolved in DMSO and imaged with an OEC Compact 7600 fluoroscope. At a tube voltage of 42 kVp, absorbance of equimolar diiodomethane (150 mM) was significantly (p<0.01) greater than iodomethane (150 mM) by 45%. Interestingly, 150 mM diiodomethane absorbance was significantly greater than 300 mM iodomethane (by 5%, p<0.01) despite equal amounts of iodine in both solutions. 1,3-diiodobenzene absorbance was significantly greater than 1,2- and 1,4-diiodobenzene (p<0.01). However, 2,6-diiodo-4-nitroanaline absorbance was similar to 1,3-diiodobenzene. When a linear model was fit for absorbance as a function of density and harmonic error (the fractional remainder of the inter-iodine distance and the K-shell ionizing wavelength) at different beam energies, a significant overall fit was obtained for both unfiltered and hardened beams (p<0.01). While the slope of absorbance as a function of harmonic error was significant for all conditions (p<0.01), the slope with respect to density was significant only when the beam was unfiltered (p<0.05). Also harmonic error, but not density, displayed significant energy-dependent effects on absorbance (p<0.01). These data suggest that harmonic error is a strong determinant of absorbance, particularly when the beam energy is concentrated near the iodine K-edge and is likely a descriptor of K-characteristic photon interactions. Therefore, x-ray absorbance may be modulated by the distance between covalently linked x-ray K-edge attenuating atoms. This finding has important implications for increasing contrast agent absorbance as well as for designing molecular transducers capable of modulating K-edge attenuating atomic distances and thereby x-ray absorbance.
X-ray attenuation coefficient measurements for photon energies 4.508¢13.375 keV in Cu, Cr and their compounds and the validity of the mixture rule
▄ Turgut; ų ?im?ek; E B³y³kkasap; M Ertu?rul
To investigate the validity of the mixture rule which is used to compute the mass attenuation coefficients in compounds, the total mass attenuation coefficients for Cu, Cr elements and Cu2O, CuC2O4, CuCl2Ę2H2O, Cu(C2H3O2)2ĘH2O, Cr2O3, Cr(NO3)3, Cr2(SO4)3ĘH2O, Cr3(CH3CO7)(OH)2 compounds were measured at photon energies between 4.508 and 13.375keV by using the secondary excitation method. Ti, Mn, Fe, Ni, Zn, Ge, As,
Sparse signal reconstruction from polychromatic X-ray CT measurements via mass attenuation discretization
NASA Astrophysics Data System (ADS)
Gu, Renliang; Dogand×i?, Aleksandar
We propose a method for reconstructing sparse images from polychromatic x-ray computed tomography (ct) measurements via mass attenuation coefficient discretization. The material of the inspected object and the incident spectrum are assumed to be unknown. We rewrite the Lambert-Beer's law in terms of integral expressions of mass attenuation and discretize the resulting integrals. We then present a penalized constrained least-squares optimization approach for reconstructing the underlying object from log-domain measurements, where an active set approach is employed to estimate incident energy density parameters and the nonnegativity and sparsity of the image density map are imposed using negative-energy and smooth ?1-norm penalty terms. We propose a two-step scheme for refining the mass attenuation discretization grid by using higher sampling rate over the range with higher photon energy, and eliminating the discretization points that have little effect on accuracy of the forward projection model. This refinement allows us to successfully handle the characteristic lines (Dirac impulses) in the incident energy density spectrum. We compare the proposed method with the standard filtered backprojection, which ignores the polychromatic nature of the measurements and sparsity of the image density map. Numerical simulations using both realistic simulated and real x-ray ct data are presented.
Determination of total x-ray absorption coefficient using non-resonant x-ray emission
A. J. Achkar; T. Z. Regier; E. J. Monkman; K. M. Shen; D. G. Hawthorn
An alternative measure of x-ray absorption spectroscopy (XAS) called inverse partial fluorescence yield (IPFY) has recently been developed that, unlike conventional electron yield (EY) and fluorescence yield (FY) measurements, is both bulk sensitive and does not experience saturation or self-absorption effects. In this manuscript, we show that the angle dependence of IPFY can also provide a direct measure of the
On the estimation of spectral density of X-ray sources using attenuation measurements
NASA Astrophysics Data System (ADS)
Huerta, Claudia; Vazquez, Luis; Manciu, Marian; Vulcan, Teodor; Manciu, Felicia; Waggener, Robert
The high energy X-rays typically used in Medical Physics (100s kV -20 MeV ) have such short wavelengths, that creating a diffraction grating is impossible. Because the absorption coefficient depends on the wavelength, one can use transmission data through filters of various thicknesses to obtain information about the spectral density of the X-ray source. Neglecting non-linear processes, there is a linear dependence of the transmission data on the spectral distribution. Unfortunately, the corresponding underdetermined system is ill-conditioned, and traditional methods used to solve inverse problems (such as Singular Valued Decomposition) typically fails, even for very small levels of noise affecting the attenuation data (much lower than is typically obtained in an experiment). We will present a very robust algorithm for detecting the bremsstrahlung spectrum, which seek for a smooth function that minimizes the distance to the experimental transmission data. We will show that the algorithm works very well even for very noisy attenuation data, even when no prior knowledge of spectral distribution is available.
Attenuation correction of myocardial SPECT images with X-ray CT: Effects of registration errors between X-ray CT and SPECT
Yasuyuki Takahashi; Hiroshi Higashino; Teruhito Mochizuki; Nobutoku Motomura
Purpose: Attenuation correction with an X-ray CT image is a new method to correct attenuation on SPECT imaging, but the effect of\\u000a the registration errors between CT and SPECT images is unclear. In this study, we investigated the effects of the registration\\u000a errors on myocardial SPECT, analyzing data from a phantom and a human volunteer.Methods: Registerion (fusion) of the X-ray
Interference absorption coefficient of X-rays in crystals in the presence of temperature gradient
V. R. Kocharyan; R. Sh. Aleksanyan; K. G. Truni
We investigate experimentally and theoretically the behavior of the interference coefficient of absorption of X-ray radiation\\u000a of a quartz single crystal in Laue geometry in the presence of temperature gradient. The total intensity of transmitted X-ray\\u000a radiation and that reflected from different families of reflecting atomic planes of the quartz single crystal has been recorded.\\u000a It was shown that with
Building Human Brain Network in 3D Coefficient Map Determined by X-ray Microtomography
NASA Astrophysics Data System (ADS)
Mizutani, R.; Takeuchi, A.; Uesugi, K.; Takekoshi, S.; Nakamura, N.; Suzuki, Y.
X-ray microtomography can visualize 3D structures of biological soft tissues at cellular to subcellular resolution. Such 3D structures are composed of a great number of cells and extracellular matrices that should be assigned separately as tissue constituents. Here, we report a method for building a skeletonized model of the human brain network in a 3D distribution map of linear absorption coefficients determined by microtomography. The 3D models of neurons were automatically built by using a Sobel filter and manually edited via a graphical interface. The simplification of the 3D coefficient map facilitates understanding of microtomographic structures composed of huge numbers of voxels. We suggest that x-ray microtomography along with model building in the 3D coefficient map is a potential method for understanding 3D microstructures relevant to biological functions, like x-ray crystallography in molecular biology.
The X-ray attenuation characteristics and density of human calcaneal marrow do not change significantly during adulthood
NASA Technical Reports Server (NTRS)
Les, C. M.; Whalen, R. T.; Beaupre, G. S.; Yan, C. H.; Cleek, T. M.; Wills, J. S.
Changes in the material characteristics of bone marrow with aging can be a significant source of error in measurements of bone density when using X-ray and ultrasound imaging modalities. In the context of computed tomography, dual-energy computed techniques have been used to correct for changes in marrow composition. However, dual-energy quantitative computed tomography (DE-QCT) protocols, while increasing the accuracy of the measurement, reduce the precision and increase the radiation dose to the patient in comparison to single-energy quantitative computed tomography (SE-QCT) protocols. If the attenuation properties of the marrow for a particular bone can be shown to be relatively constant with age, it should be possible to use single-energy techniques without experiencing errors caused by unknown marrow composition. Marrow was extracted by centrifugation from 10 mm thick frontal sections of 34 adult cadaver calcanei (28 males, 6 females, ages 17-65 years). The density and energy-dependent linear X-ray attenuation coefficient of each marrow sample were determined. For purposes of comparing our results, we then computed an effective CT number at two GE CT/i scan voltages (80 and 120 kVp) for each specimen. The coefficients of variation for the density, CT number at 80 kVp and CT number at 120 kVp were each less than 1%, and the parameters did not change significantly with age (p > 0.2, r2 < 0.02, power > 0.8 where the minimum acceptable r2 = 0.216). We could demonstrate no significant gender-associated differences in these relationships. These data suggest that calcaneal bone marrow X-ray attenuation properties and marrow density are essentially constant from the third through sixth decades of life.
Spatial Gradients in Particle Reinforced Polymers Characterized by X-Ray Attenuation and Laser Confocal Microscopy
The goal of this work is to develop techniques for measuring gradients in particle concentration within filled polymers, such as encapsulant. A high concentration of filler particles is added to such materials to tailor physical properties such as thermal expansion coefficient. Sedimentation and flow-induced migration of particles can produce concentration gradients that are most severe near material boundaries. Therefore, techniques for measuring local particle concentration should be accurate near boundaries. Particle gradients in an alumina-filled epoxy resin are measured with a spatial resolution of 0.2 mm using an x-ray beam attenuation technique, but an artifact related to the finite diameter of the beam reduces accuracy near the specimen's edge. Local particle concentration near an edge can be measured more reliably using microscopy coupled with image analysis. This is illustrated by measuring concentration profiles of glass particles having 40 {micro}m median diameter using images acquired by a confocal laser fluorescence microscope. The mean of the measured profiles of volume fraction agrees to better than 3% with the expected value, and the shape of the profiles agrees qualitatively with simple theory for sedimentation of monodisperse particles. Extending this microscopy technique to smaller, micron-scale filler particles used in encapsulant for microelectronic devices is illustrated by measuring the local concentration of an epoxy resin containing 0.41 volume fraction of silica.
X-ray pulsing methods for reduced-dose computed tomography in PET/CT attenuation correction
NASA Astrophysics Data System (ADS)
Wiedmann, Uwe; Neculaes, V. Bogdan; Harrison, Dan; Asma, Evren; Kinahan, Paul E.; De Man, Bruno
The image quality needed for CT-based attenuation correction (CTAC) is significantly lower than what is used currently for diagnostic CT imaging. Consequently, the X-ray dose required for sufficient image quality with CTAC is relatively small, potentially smaller than the lowest X-ray dose clinical CT scanners can provide. Operating modes have been proposed in which the X-rays are periodically turned on and off during the scan in order to reduce X-ray dose. This study reviews the different methods by which X-rays can be modulated in a CT scanner, and assesses their adequacy for lowdose acquisitions as required for CTAC. Calculations and experimental data are provided to exemplify selected X-ray pulsing scenarios. Our analysis shows that low-dose pulsing is possible but challenging with clinically available CT tubes. Alternative X-ray tube designs would lift this restriction.
Research on reducing radiation exposure for clinical applications of X-ray attenuation
NASA Astrophysics Data System (ADS)
Jeon, Min-Cheol; Han, Man-Seok; So, Woon-Young; Lee, Hyeon-Guck; Kim, Yong-Kyun; Lee, Seung-Yeol
This study was aimed at identifing areas with low radiation exposure where workers could be taken in the examination room in case that they had to hold the patients by estimating the attenuation of primary radiation and measuring the spatial distribution of scattered radiation. The laboratory equipment included on the X-ray generator, a phantom (human phantom), and a dosimeter. The experiment measured the performance of the examination system (dose reproducibility), the dose of primary radiation (X-rays), and the dose of scattered radiation (secondary radiation). Both the primary and the scattered radiation were attenuated by a factor of tube in vacuum experimental tests of the inverse square law. In this study, the attenuation was 2 ś 2.246 for primary radiation and 2 ś 2.105 for secondary radiation. Natural attenuation occurred as the X-rays passed through air, and an attenuation equation was established in this study. The equation for primary radiation (1st dose) was y = A1* exp(- x/t1)+ y0. The high-intensity contour of the direction for the cathode was wider than that of the direction for the anode, showing a wide range on the rear side of the cathode and on the rear side of the anode. We tried to find the positions where the workers' radiation exposure could be reduced. When the medical radiation workers have to hold the patient for an abdominal examination, they should be placed towards the tube anode and on the left side of the patient. For a lumbar-spine lateral examination, they should be placed towards the tube anode and behind the patient, and for a femur AP (anterior-posterior) examination, they should be placed towards the tube anode and on the right side of the patient.
An elastically compressible phantom material with mechanical and x-ray attenuation properties equivalent to breast tissue
NASA Astrophysics Data System (ADS)
Price, B. D.; Gibson, A. P.; Tan, L. T.; Royle, G. J.
We have developed a novel phantom material: a solution of polyvinyl alcohol (PVAL) in ethanol and water, freeze-thawed to produce a solid yet elastically compressible gel. The x-ray attenuation and mechanical properties of these gels are compared with published measurements of breast tissue. Gels with PVAL concentrations from 5 to 20% w/v were produced. The linear x-ray attenuation coefficients of these gels range from 0.76 to 0.86 cm-1 at 17.5 keV, increasing with PVAL concentration. These values are very similar to the published values of breast tissue at this energy, 0.8-0.9 cm-1. Under compression cancerous breast tissue is approximately ten times stiffer than healthy breast tissue. The Young's moduli of the gels increase with PVAL concentration. Varying the PVAL concentration from 7.5 to 20% w/v produces gels with Young's moduli from 20 to 220 kPa at 15% strain. These values are characteristic of normal and cancerous breast tissue, respectively.
Attenuation coefficients of Rayleigh and Lg waves
Igor B. Morozov
Analysis of the frequency dependence of the attenuation coefficient leads to significant changes in interpretation of seismic\\u000a attenuation data. Here, several published surface-wave attenuation studies are revisited from a uniform viewpoint of the temporal\\u000a attenuation coefficient, denoted by ?. Theoretically, ?( f) is expected to be linear in frequency, with a generally non-zero intercept ??=??(0) related to the variations of
Imaging method based on attenuation, refraction and ultra-small-angle-scattering of x-rays
Wernick, Miles N.; Chapman, Leroy Dean; Oltulu, Oral; Zhong, Zhong
A method for detecting an image of an object by measuring the intensity at a plurality of positions of a transmitted beam of x-ray radiation emitted from the object as a function of angle within the transmitted beam. The intensity measurements of the transmitted beam are obtained by a crystal analyzer positioned at a plurality of angular positions. The plurality of intensity measurements are used to determine the angular intensity spectrum of the transmitted beam. One or more parameters, such as an attenuation property, a refraction property and a scatter property, can be obtained from the angular intensity spectrum and used to display an image of the object.
Neutron Analysis for Microvoids in an Adhesive Layer between High X-ray Attenuation Materials
NASA Astrophysics Data System (ADS)
Nguyen, Thanhhai; Vavrik, Daniel; Lehmann, Eberhard H.; Jeon, Insu
We demonstrate the potential of neutron systems for detecting microscale defects in a thin epoxy adhesive layer between two metal plates. Neutron tomography has been used to ascertain the internal structure of the adhesive layer. The distribution of defects including microvoids is found in three-dimensionally reconstructed models that are obtained from neutron tomography images and is compared with that obtained from a magnified real image of the layer. From the results, we find that a neutron system can be the most suitable tool for detecting microscale defects in a thin adhesive layer that lies between two high X-ray attenuation plates.
Measurement of atomic number and mass attenuation coefficient in magnesium ferrite
R. H. Kadam; S. T. Alone; G. K. Bichile; K. M. Jadhav
Pure magnesium ferrite sample was prepared by standard ceramic technique and characterized by X-ray diffraction method. XRD pattern revealed that the sample possess single-phase cubic spinel structure. The linear attenuation coefficient (mu), mass attenuation coefficient (mu\\/rho), total atomic cross-section (sigma_{tot}), total electronic cross-section (sigma_{ele}) and the effective atomic number (Z_{eff}) were calculated for pure magnesium ferrite (MgFe_{2}O_{4}). The values of
Estimation of effective x-ray tissue attenuation differences for volumetric breast density measurement
NASA Astrophysics Data System (ADS)
Chen, Biao; Ruth, Chris; Jing, Zhenxue; Ren, Baorui; Smith, Andrew; Kshirsagar, Ashwini
Breast density has been identified to be a risk factor of developing breast cancer and an indicator of lesion diagnostic obstruction due to masking effect. Volumetric density measurement evaluates fibro-glandular volume, breast volume, and breast volume density measures that have potential advantages over area density measurement in risk assessment. One class of volume density computing methods is based on the finding of the relative fibro-glandular tissue attenuation with regards to the reference fat tissue, and the estimation of the effective x-ray tissue attenuation differences between the fibro-glandular and fat tissue is key to volumetric breast density computing. We have modeled the effective attenuation difference as a function of actual x-ray skin entrance spectrum, breast thickness, fibro-glandular tissue thickness distribution, and detector efficiency. Compared to other approaches, our method has threefold advantages: (1) avoids the system calibration-based creation of effective attenuation differences which may introduce tedious calibrations for each imaging system and may not reflect the spectrum change and scatter induced overestimation or underestimation of breast density; (2) obtains the system specific separate and differential attenuation values of fibroglandular and fat for each mammographic image; and (3) further reduces the impact of breast thickness accuracy to volumetric breast density. A quantitative breast volume phantom with a set of equivalent fibro-glandular thicknesses has been used to evaluate the volume breast density measurement with the proposed method. The experimental results have shown that the method has significantly improved the accuracy of estimating breast density.
Measurements of Gamma-Ray Attenuation Coefficients
B. Goswami; N. Chaudhuri
Measurements have been made to determine gamma-ray attenuation coefficients very accurately by using an extremely-narrow-collimated-beam transmission method which effectively excluded corrections due to small-angle and multiple scattering of photons. The measured mass attenuation coefficients with maximum errors less than 3% for 34 elements in the range from hydrogen to lead are given.
Attenuation of x-ray in muscle and alveolar bone during mandibular premolar periapical radiographic procedure.
Chiu, P C; Yan, Y H; Lin, L M; Chang, P S
The main purpose of this study is to find out the degree of attenuation when the x-ray entrances the skin and reaches the film at the bone area near the mandibular premolar root apex. In this study we used thermaluminescent dosimeters (TLDs) to measure the entrance dose and exit dose directly at the area of interest and calculated the penetration value P. We also simulated the attenuation process and calculated the P value in similar conditions. The results indicate that the mean P value of direct measurement from patient is 0.071 +/- 0.018 (60kVp, HVL = 1.5mm Al), while that for theoretical calculation is 0.06458 at 27keV. We concluded that P value of direct measurement can match with the theoretical value and further studies in jaw bone density and other related portions is worthwhile. PMID:9385780
Correction of nonuniform attenuation and image fusion in SPECT imaging by means of separate X-ray CT
Toru Kashiwagi; Kenji Yutani; Minoru Fukuchi; Hitoshi Naruse; Tadaaki Iwasaki; Koichi Yokozuka; Shinichi Inoue; Shoji Kondo
Improvements in image quality and quantitation measurement, and the addition of detailed anatomical structures are important\\u000a topics for single-photon emission tomography (SPECT). The goal of this study was to develop a practical system enabling both\\u000a nonuniform attenuation correction and image fusion of SPECT images by means of high-performance X-ray computed tomography\\u000a (CT). A SPECT system and a helical X-ray CT
X-rays in Atomic and Nuclear Physics
NASA Astrophysics Data System (ADS)
Dyson, N. A.
Preface to the second edition; Preface to the first edition; 1. Historical introduction; 2. The continuous X-ray spectrum; 3. Characteristic X-rays; 4. Experimental techniques for the study of X-rays; 5. The absorption and scattering of X-rays; 6. X-ray production by protons, ?-particles and heavy ions; 7. X-rays in radioactive decay; 8. Some additional fields of X-ray study; Appendix 1. Range energy relations, etc., for electrons; 2. Experimentally determined mass attenuation coefficients; 3. Decay schemes of some radionuclides; 4. Absorption edges and characteristic emission energies in keV; 5. K-shell fluorescence yields; Bibliography; Index.
Gamma-Ray Attenuation Coefficient Measurements
S. Gopal; B. Sanjeevaiah
In an earlier paper, published by the authors elsewhere, it was shown that for 661.6-keV gamma rays the measurements of gamma-ray attenuation coefficients would greatly improve if one uses the counting sequence of Conner et al. together with a new criterion mut<1, where mu is the gamma-ray attenuation coefficient and t is the thickness of the sample. In this paper
Flat panel X-ray detector with reduced internal scattering for improved attenuation accuracy and dynamic range
Smith, Peter D. (Santa Fe, NM); Claytor, Thomas N. (White Rock, NM); Berry, Phillip C. (Albuquerque, NM); Hills, Charles R. (Los Alamos, NM)
An x-ray detector is disclosed that has had all unnecessary material removed from the x-ray beam path, and all of the remaining material in the beam path made as light and as low in atomic number as possible. The resulting detector is essentially transparent to x-rays and, thus, has greatly reduced internal scatter. The result of this is that x-ray attenuation data measured for the object under examination are much more accurate and have an increased dynamic range. The benefits of this improvement are that beam hardening corrections can be made accurately, that computed tomography reconstructions can be used for quantitative determination of material properties including density and atomic number, and that lower exposures may be possible as a result of the increased dynamic range.
Measurement of $gamma$-ray attenuation coefficients
Gamma-ray attenuation coefficients have been determined for aluminum, ; copper, tin, platinum and lead (elements with Z between 13 and 82) using gamma -; rays with energies between 295 and 2440 keV from a sealed Ra-226 source. A ; lithium-drifted germanium detector was employed without collimation or shielding. ; The average standard error of the experimental results was 1%. (auth)
Measurement of atomic number and mass attenuation coefficient in magnesium ferrite
R H Kadam; S T Alone; G K Bichile; K M Jadhav
Pure magnesium ferrite sample was prepared by standard ceramic technique and characterized by X-ray diffraction method. XRD\\u000a pattern revealed that the sample possess single-phase cubic spinel structure. The linear attenuation coefficient (Ą), mass attenuation coefficient (Ą\\/?), total atomic cross-section (?\\u000a tot), total electronic cross-section (?\\u000a ele) and the effective atomic number (Z\\u000a eff) were calculated for pure magnesium ferrite (MgFe2O4).
Analytical ansatz for self-consistent calculations of x-ray transmission and reflection coefficients at graded interfaces
NASA Astrophysics Data System (ADS)
Feranchuk, I. D.; Feranchuk, S. I.; Komarov, L.; Sytova, S.; Ulyanenkov, A.
We propose a particular analytical representation (ansatz) for analytical solution of MaxwellÆs equations with one-dimensional potential. The resulting expressions are presented as self-consistent equations for the calculation of x-ray reflection and transmission coefficients at the interfaces with an arbitrary potential profile. The reported approach is testified for typical model potentials, and the convergence of the successive iterations for improvement of solution accuracy is demonstrated. The equations derived in the paper can be used for the solution of the inverse problem in x-ray reflectometry.
Measurement of the linear attenuation coefficients of breast tissues by synchrotron radiation computed tomography
NASA Astrophysics Data System (ADS)
Chen, R. C.; Longo, R.; Rigon, L.; Zanconati, F.; De Pellegrin, A.; Arfelli, F.; Dreossi, D.; Menk, R.-H.; Vallazza, E.; Xiao, T. Q.; Castelli, E.
The measurement of the linear attenuation coefficients of breast tissues is of fundamental importance in the field of breast x-ray diagnostic imaging. Different groups have evaluated the linear attenuation coefficients of breast tissues by carrying out direct attenuation measurements in which the specimens were thin and selected as homogeneous as possible. Here, we use monochromatic and high-intensity synchrotron radiation computed tomography (SR CT) to evaluate the linear attenuation coefficients of surgical breast tissues in the energy range from 15 to 26.5 keV. X-ray detection is performed by a custom digital silicon micro-strip device, developed in the framework of the PICASSO INFN experiment. Twenty-three human surgical breast samples were selected for SR CT and histological study. Six of them underwent CT, both as fresh tissue and after formalin fixation, while the remaining 17 were imaged only as formalin-fixed tissues. Our results for fat and fibrous tissues are in good agreement with the published values. However, in contrast to the published data, our measurements show no significant differences between fibrous and tumor tissues. Moreover, our results for fresh and formalin-fixed tissues demonstrate a reduction of the linear attenuation coefficient for fibrous and tumor tissues after fixation.
Determination of attenuation coefficients, thicknesses and effective atomic numbers for CuInSe 2 semiconductor
Hasan Baltas; Ahmet Ūelik; Emin Bacaksiz
The X-rays attenuation coefficients for Cu, In and Se in elemental state and the semiconductor CuInSe2 were measured at 15 different energies from 11.9 to 37.3keV by using the secondary excitation method. Monochromatic photons were obtained using the following secondary targets: Br, Sr, Mo, Cd, Te and Ba. 59.5keV gamma rays emitted from an annular 241Am radioactive source were used
Comparison of the x-ray attenuation properties of breast calcifications, aluminium, hydroxyapatite and calcium oxalate
NASA Astrophysics Data System (ADS)
Warren, L. M.; Mackenzie, A.; Dance, D. R.; Young, K. C.
Aluminium is often used as a substitute material for calcifications in phantom measurements in mammography. Additionally, calcium oxalate, hydroxyapatite and aluminium are used in simulation studies. This assumes that these materials have similar attenuation properties to calcification, and this assumption is examined in this work. Sliced mastectomy samples containing calcification were imaged at ū5 magnification using a digital specimen cabinet. Images of the individual calcifications were extracted, and the diameter and contrast of each calculated. The thicknesses of aluminium required to achieve the same contrast as each calcification when imaged under the same conditions were calculated using measurements of the contrast of aluminium foils. As hydroxyapatite and calcium oxalate are also used to simulate calcifications, the equivalent aluminium thicknesses of these materials were also calculated using tabulated attenuation coefficients. On average the equivalent aluminium thickness was 0.85 times the calcification diameter. For calcium oxalate and hydroxyapatite, the equivalent aluminium thicknesses were 1.01 and 2.19 times the thickness of these materials respectively. Aluminium and calcium oxalate are suitable substitute materials for calcifications. Hydroxyapatite is much more attenuating than the calcifications and aluminium. Using solid hydroxyapatite as a substitute for calcification of the same size would lead to excessive contrast in the mammographic image.
Comparison of the x-ray attenuation properties of breast calcifications, aluminium, hydroxyapatite and calcium oxalate.
Warren, L M; Mackenzie, A; Dance, D R; Young, K C
Aluminium is often used as a substitute material for calcifications in phantom measurements in mammography. Additionally, calcium oxalate, hydroxyapatite and aluminium are used in simulation studies. This assumes that these materials have similar attenuation properties to calcification, and this assumption is examined in this work. Sliced mastectomy samples containing calcification were imaged atĀū5 magnification using a digital specimen cabinet. Images of the individual calcifications were extracted, and the diameter and contrast of each calculated. The thicknesses of aluminium required to achieve the same contrast as each calcification when imaged under the same conditions were calculated using measurements of the contrast of aluminium foils. As hydroxyapatite and calcium oxalate are also used to simulate calcifications, the equivalent aluminium thicknesses of these materials were also calculated using tabulated attenuation coefficients. On average the equivalent aluminium thickness was 0.85Ātimes the calcification diameter. For calcium oxalate and hydroxyapatite, the equivalent aluminium thicknesses were 1.01 and 2.19Ātimes the thickness of these materials respectively. Aluminium and calcium oxalate are suitable substitute materials for calcifications. Hydroxyapatite is much more attenuating than the calcifications and aluminium. Using solid hydroxyapatite as a substitute for calcification of the same size would lead to excessive contrast in the mammographic image. PMID:23470559
Unbiased Estimation of Atmosphere Attenuation Coefficient
G. D. Dikic; Z. M. Djurovic
According to the passive sensorsÆ nature, only the azimuth and elevation angles are used for the target state estimation.\\u000a In some scenarios, additional information like the irradiances generated by the passive sensors must be introduced to improve\\u000a the estimation process. On the other hand, irradiances are strongly dependent on the atmosphere properties that may be described\\u000a by attenuation coefficient. An
Linear attenuation coefficients for compensator based imrt
T. Bartrum; M. Bailey; V. Nelson; M. Grace
With rapid technological improvements in computer driven 3-D radiotherapy treatment planning systems (RTPS) the use of compensating\\u000a filters for intensity modulated radiation therapy (IMRT) will dramatically increase the ease of treatment. The procedure for\\u000a commissioning .decimalÖ (Sanford, Florida) compensators involved the measurement of the effective linear attenuation coefficients\\u000a for aluminium and brass. Field sizes to be measured vary from small
Gamma-Ray Attenuation-Coefficient Measurements
A. L. Conner; H. F. Atwater; Elizabeth H. Plassmann; J. H. McCrary
Total gamma-ray attenuation coefficients have been measured at nine energies in the range of 88 keV to 2.75 MeV for the following elements: Be, C, Mg, Al, S, Ti, Fe, Ni, Cu, Zn, Zr, Nb, Mo, Ag, Sn, La, Gd, Hf, W, Au, Pb, Th, U, and Pu. Radioactive isotopes were used as sources of monoenergetic gamma radiation in a
Noninvasive Femur Bone Volume Estimation Based on X-Ray Attenuation of a Single Radiographic Image and Medical Knowledge
NASA Astrophysics Data System (ADS)
Kiattisin, Supaporn; Chamnongthai, Kosin
Bone Mineral Density (BMD) is an indicator of osteoporosis that is an increasingly serious disease, particularly for the elderly. To calculate BMD, we need to measure the volume of the femur in a noninvasive way. In this paper, we propose a noninvasive bone volume measurement method using x-ray attenuation on radiography and medical knowledge. The absolute thickness at one reference pixel and the relative thickness at all pixels of the bone in the x-ray image are used to calculate the volume and the BMD. First, the absolute bone thickness of one particular pixel is estimated by the known geometric shape of a specific bone part as medical knowledge. The relative bone thicknesses of all pixels are then calculated by x-ray attenuation of each pixel. Finally, given the absolute bone thickness of the reference pixel, the absolute bone thickness of all pixels is mapped. To evaluate the performance of the proposed method, experiments on 300 subjects were performed. We found that the method provides good estimations of real BMD values of femur bone. Estimates shows a high linear correlation of 0.96 between the volume Bone Mineral Density (vBMD) of CT-SCAN and computed vBMD (all P<0.001). The BMD results reveal 3.23% difference in volume from the BMD of CT-SCAN.
X-ray attenuation of the liver and kidney in cats considered at varying risk of hepatic lipidosis.
Lam, Richard; Niessen, Stijn J; Lamb, Christopher R
X-ray attenuation of the liver has been measured using computed tomography (CT) and reported to decrease in cats with experimentally induced hepatic lipidosis. To assess the clinical utility of this technique, medical records and noncontrast CT scans of a series of cats were retrospectively reviewed. A total of 112 cats met inclusion criteria and were stratified into three hepatic lipidosis risk groups. Group 1 cats were considered low-risk based on no history of inappetence or weight loss, and normal serum chemistry values; Group 2 cats were considered intermediate risk based on weight loss, serum hepatic enzymes above normal limits, or reasonably controlled diabetes mellitus; and Group 3 cats were considered high risk based on poorly controlled diabetes mellitus due to hypersomatotropism. Mean CT attenuation values (Hounsfield units, HU) were measured using regions of interest placed within the liver and cranial pole of the right kidney. Hepatic and renal attenuation were weakly positively correlated with each other (r = 0.2, P = 0.03) and weakly negatively correlated with body weight (r = -0.21, P = 0.05, and r = -0.34, P = 0.001, respectively). Mean (SD) hepatic and renal cortical attenuation values were 70.7 (8.7) HU and 49.6 (9.2) HU for Group 1 cats, 71.4 (7.9) HU and 48.6 (9.1) HU for Group 2, and 68.9 (7.6) HU and 47.6 (7.2) HU for Group 3. There were no significant differences in hepatic or renal attenuation among groups. Findings indicated that CT measures of X-ray attenuation in the liver and kidney may not be accurate predictors of naturally occurring hepatic lipidosis in cats. PMID:24131209
Scattered X-ray beam nondestructive testing
G. Harding; J. Kosanetzky
X-ray scatter interactions generally dominate the linear attenuation coefficient at the photon energies typical of medical and industrial radiography. Specific advantages of X-ray scatter imaging, including a flexible choice of measurement geometry, direct 3D-imaging capability (tomography) and improved information for material characterization, are illustrated with results from Compton and coherent scatter devices. Applications of a Compton backscatter scanner (ComScan) in
Infrared Radiography: Modeling X-ray Imaging without Harmful Radiation
ERIC Educational Resources Information Center
Zietz, Otto; Mylott, Elliot; Widenhorn, Ralf
Planar x-ray imaging is a ubiquitous diagnostic tool and is routinely performed to diagnose conditions as varied as bone fractures and pneumonia. The underlying principle is that the varying attenuation coefficients of air, water, tissue, bone, or metal implants within the body result in non-uniform transmission of x-ray radiation. Through theģ
X-ray Microtomographic Imaging and Analysis for Basic Research
J. Dunsmuir; S. Bennett; L. Fareria; A. Mingino; M. Sansone
For research facilities with access to synchrotron X-ray sources, X-ray absorption microtomography (XMT) has evolved from an experimental imaging method to a specialized, if not yet routine, microscopy for imaging the three-dimensional (3D) distribution of linear attenuation coefficients and, in some cases, elemental concentration with micron spatial resolution. Recent advances in source and detector design have produced conventional X-ray source
Model based 3D CS-catheter tracking from 2D X-ray projections: binary versus attenuation models.
Haase, Christian; Schõfer, Dirk; D÷ssel, Olaf; Grass, Michael
Tracking the location of medical devices in interventional X-ray data solves different problems. For example the motion information of the devices is used to determine cardiac or respiratory motion during X-ray guided procedures or device features are used as landmarks to register images. In this publication an approach using a 3D deformable catheter model is presented and used to track a coronary sinus (CS) catheter in 3D plus time through a complete rotational angiography sequence. The benefits of using voxel based models with attenuation information for 2D/3D registration are investigated in comparison to binary catheter models. The 2D/3D registration of the model allows to extract a 3D catheter shape from every individual 2D projection. The tracking accuracy is evaluated on simulated and clinical rotational angiography data of the contrast enhanced left atrium. The quantitative evaluation of the experiments delivers an average registration accuracy for all catheter electrodes of 0.23 mm in 2D and 0.95 mm in 3D when using an attenuation model of the catheter. The overall tracking accuracy is lower when using binary catheter models. PMID:24444681
Initial study of quasimonochromatic X-ray beam performance for X-ray computed mammotomography
Randolph L. McKinley; Martin P. Tornai; Ehsan Samei; Marques L. Bradshaw
We evaluate the feasibility, benefits, and operating parameters of a quasimonochromatic beam for a newly developed X-ray cone beam computed mammotomography application. The value of a near monochromatic X-ray source for a fully 3D tomography application is the expected improved ability to separate tissues with very small differences in attenuation coefficients while maintaining dose level at or below existing dual
Gamma-ray attenuation coefficients for human tissues
P S Rao; E C Gregg
The diagnosis of soft tissue disease such as cancer by radiographic means depends to some extent on the difference in the attenuation of gamma -rays in healthy and diseased tissues. Since devices for imaging very small changes in attenuation are now being introduced, a more exact knowledge of such attenuation coefficients in various tissues would be of help in the
A generalized method of converting CT image to PET linear attenuation coefficient distribution in PET/CT imaging
NASA Astrophysics Data System (ADS)
Wang, Lu; Wu, Li-Wei; Wei, Le; Gao, Juan; Sun, Cui-Li; Chai, Pei; Li, Dao-Wu
The accuracy of attenuation correction in positron emission tomography scanners depends mainly on deriving the reliable 511-keV linear attenuation coefficient distribution in the scanned objects. In the PET/CT system, the linear attenuation distribution is usually obtained from the intensities of the CT image. However, the intensities of the CT image relate to the attenuation of photons in an energy range of 40 keV-140 keV. Before implementing PET attenuation correction, the intensities of CT images must be transformed into the PET 511-keV linear attenuation coefficients. However, the CT scan parameters can affect the effective energy of CT X-ray photons and thus affect the intensities of the CT image. Therefore, for PET/CT attenuation correction, it is crucial to determine the conversion curve with a given set of CT scan parameters and convert the CT image into a PET linear attenuation coefficient distribution. A generalized method is proposed for converting a CT image into a PET linear attenuation coefficient distribution. Instead of some parameter-dependent phantom calibration experiments, the conversion curve is calculated directly by employing the consistency conditions to yield the most consistent attenuation map with the measured PET data. The method is evaluated with phantom experiments and small animal experiments. In phantom studies, the estimated conversion curve fits the true attenuation coefficients accurately, and accurate PET attenuation maps are obtained by the estimated conversion curves and provide nearly the same correction results as the true attenuation map. In small animal studies, a more complicated attenuation distribution of the mouse is obtained successfully to remove the attenuation artifact and improve the PET image contrast efficiently.
Mammography spectrum measurement using an x-ray diffraction device
NASA Astrophysics Data System (ADS)
Boone, John M.; Yu, Tong; Seibert, Anthony
The use of a diffraction spectrometer developed by Deslattes for the determination of mammographic kV is extended to the measurement of accurate, relative x-ray spectra. Raw x-ray spectra (photon fluence versus energy) are determined by passing an x-ray beam through a bent quartz diffraction crystal, and the diffracted x-rays are detected by an x-ray intensifying screen coupled to a charge coupled device. Two nonlinear correction procedures, one operating on the energy axis and the other operating on the fluence axis, are described and performed on measured x-ray spectra. The corrected x-ray spectra are compared against tabulated x-ray spectra measured under nearly identical conditions. Results indicate that the current device is capable of producing accurate relative x-ray spectral measurements in the energy region from 12 keV to 40 keV, which represents most of the screen-film mammography energy range. Twelve keV is the low-energy cut-off, due to the design geometry of the device. The spectrometer was also used to determine the energy-dependent x-ray mass attenuation coefficients for aluminium, with excellent results in the 12-30 keV range. Additional utility of the device for accurately determining the attenuation characteristics of various normal and abnormal breast tissues and phantom substitutes is anticipated.
Linear attenuation coefficients of tissues from 1 keV to 150 keV
NASA Astrophysics Data System (ADS)
B÷ke, Aysun
The linear attenuation coefficients and three interaction processes have been computed for liver, kidney, muscle, fat and for a range of x-ray energies from 1 keV to 150 keV. Molecular photoelectric absorption cross sections were calculated from atomic cross section data. Total coherent (Rayleigh) and incoherent (Compton) scattering cross sections were obtained by numerical integration over combinations of F2m(x) with the Thomson formula and Sm(x) with the Klein-Nishina formula, respectively. For the coherent (Rayleigh) scattering cross section calculations, molecular form factors were obtained from recent experimental data in the literature for values of x<1 ┼-1 and from the relativistic modified atomic form factors for values of x?1 ┼-1. With the inclusion of molecular interference effects in the coherent (Rayleigh) scattering, more accurate knowledge of the scatter from these tissues will be provided. The number of elements involved in tissue composition is 5 for liver, 47 for kidney, 44 for muscle and 3 for fat. The results are compared with previously published experimental and theoretical linear attenuation coefficients. In general, good agreement is obtained. The molecular form factors and scattering functions and cross sections are incorporated into a Monte Carlo program. The energy distributions of x-ray photons scattered from tissues have been simulated and the results are presented.
Gamma Ray Attenuation Coefficient of Microalloyed Stainless Steel
I. Akkurt; H. Aky?ld?r?m; A. Calik; O. B. Aytar; N. Uńar
Gamma ray attenuation coefficients of microalloyed steel have been investigated. For this purposes the linear attenuation\\u000a coefficients of steel have been measured at the photon energy of 0.662, 1.173 and 1.332ĀMeV and the results were compared\\u000a with the calculation at the photon energy of 1¢105ĀMeV obtained using XCOM.
Electron-ion recombination rate coefficients and photoionization cross-sections for Al XI, Al XII, Si XII, Si XIII for UV and X-ray modeling
Nahar, Sultana Nurun
Electron-ion recombination rate coefficients and photoionization cross-sections for Al XI, Al XII-ion recombination UV and X-rays Al XI, Al XII, Si XII, Si XIII a b s t r a c t Results are presented from detailed study of inverse processes of photoionization and electron-ion recombination of (hm + Al XI Al XII + e
Optical attenuation coefficient in individual ZnO nanowires.
Little, Anree; Hoffman, Abigail; Haegel, Nancy M
Attenuation coefficient measurements for the propagation of bandedge luminescence are made on individual ZnO nanowires by combining the localized excitation capability of a scanning electron microscope (SEM) with near-field scanning optical microscopy (NSOM) to record the distribution and intensity of wave-guided emission. Measurements were made for individual nanostructures with triangular cross-sections ranging in diameter from 680 to 2300 nm. The effective attenuation coefficient shows an inverse dependence on nanowire diameter (d(-1)), indicating scattering losses due to non-ideal waveguiding behavior. PMID:23482201
Hygrothermal degradation of 3-glycidoxypropyltrimethoxysilane films studied by neutron and X-ray reflectivity and attenuated total reflection infrared spectroscopy.
Tallant, David Robert; Garcia, Manuel Joseph; Majewski, Jaroslaw (Los Alamos National Lab, Los Alamos, NM); Kent, Michael Stuart; Yim, Hyun
Thin films of organosilanes have great technological importance in the areas of adhesion promotion, durability, and corrosion resistance. However, it is well-known that water can degrade organosilane films, particularly at elevated temperatures. In this work, X-ray and neutron reflectivity (XR and NR) were combined with attenuated total reflection infrared (ATR-IR) spectroscopy to study the chemical and structural changes within thin films of (3-glycidoxypropyl)trimethoxysilane (GPS) after exposure for various periods of time to air saturated with either D{sub 2}O or H{sub 2}O at 80 C. For NR and XR, ultrathin ({approx}100 {angstrom}) films were prepared by spin-coating. Both D{sub 2}O and H{sub 2}O provide neutron scattering contrast with GPS. Variations in the neutron scattering length density (SLD) profiles (a function of mass density and atomic composition) with conditioning time were measured after drying the samples out and also swelled with H{sub 2}O or D{sub 2}O vapor at room temperature. For samples that were dried out prior to measurement, little or no change was observed for H{sub 2}O conditioning up to 3.5 days, but large changes were observed after 30 days of conditioning. The range of conditioning time for this structural change was narrowed to between 4 and 10 days with XR. The SLD profiles indicated that the top portion of the GPS film was transformed into a thick low-density layer after conditioning, but the bottom portion showed little structural change. A previous NR study of as-prepared GPS films involving swelling with deuterated nitrobenzene showed that the central portion of the film has much lower cross-link density than the region nearest the substrate. The present data show that the central portion also swells to a much greater extent with water and hydrolyzes more rapidly. The chemical degradation mechanism was identified by IR as hydrolysis of siloxane bonds. For ATR-IR, GPS films were prepared by dip-coating, which resulted in a greater and more variable thickness than for the spin-coated samples. The IR spectra revealed an increase in vicinal silanol generation over the first 3 days of conditioning followed by geminal silanol generation. Thus, the structural change detected by NR and XR roughly coincided with the onset of geminal silanol generation. Finally, little change in the reflectivity data was observed for films conditioned with D{sub 2}O at 80 C for 1 month. This indicates that hydrolysis of Si-O-Si is much slower with D{sub 2}O than with H{sub 2}O.
Determination of mass attenuation coefficients for threshold contrast evaluation in digital mammography
NASA Astrophysics Data System (ADS)
Hummel, Johann; Semturs, Friedrich; Menhart, Susanne; Figl, Michael
According to the 'European protocol for the quality control of the physical and technical aspects of mammography screening' (EPQC) image quality digital mammography units has to be evaluated at different breast thicknesses. At the standard thickness of 50 mm polymethyl methacrylate (PMMA) image quality is determined by the analysis of CDMAM contrast detail phantom images where threshold contrasts are calculated for different gold disc diameters. To extend these results to other breast thicknesses contrast-to-noise ratios (CNR) and threshold contrast (TC) visibilities have to be calculated for all required thicknesses. To calculate the latter the mass attenuation coefficient (MAC) of gold has to be known for all possible beam qualities in the tube voltage range between 26 and 32 kV. In this paper we first determined the threshold contrast visibility using the CDMAM phantom with the same beam quality at different current-time products (mAs). We can derive from Rose theory that CNR Ģ CT Ģ ? = const, where ? is the diameter of the gold cylinder. From this the corresponding attenuation coefficients can be calculated. This procedure was repeated for four different beam qualities (Mo/Mo 27kV, Rh/Rh 29kV, Rh/Rh 31 kV, and W/Rh 29 kV)). Next, we measured the aluminium half value layer (HVL) of all x-ray spectra relevant for mammography. Using a first order Taylor expansion of MAC as a function of HVL, all other desired MAC can be calculated. The MAC as a function of the HVL was derived to MAChvl = -286.97 * hvl+186.03 with R2 = 0.997, where MAChvl indicates the MAC for all specific x-ray spectrum defined by its aluminium half value layer. Based on this function all necessary MACs needed for quality assurance (QA) were calculated. The results were in good agreement with the data found in the protocol.
Measurement of Acoustic Attenuation and Absorption Coefficients using Thermometry
Hugh Morris; Ian Rivens; Adam Shaw; Gail Ter Haar
Accurate knowledge of both the attenuation and the absorption coefficient of tissue are required when planning an optimal high intensity focused ultrasound treatment. A novel technique for simple measurement of this parameters has been developed in which a thin-film thermocouple (TFT) is placed between two layers of tissue of different thicknesses. The sample can be rotated about an axis through
Gamma-ray attenuation coefficients in bismuth borate glasses
Kulwant Singh; Harvinder Singh; Vishal Sharma; Rohila Nathuram; Atul Khanna; Rajesh Kumar; Surjit Singh Bhatti; Hari Singh Sahota
Mass attenuation coefficients of glasses in the system: xBi2O3(1?x)B2O3 (x=0.30, 0.35, 0.40, 0.45 and 0.55) were determined at 356, 662, 1173 and 1332 keV photon energies using a narrow beam transmission method. Appreciable variations were observed in these coefficients due to changes in the chemical composition of glasses. These coefficients were then used to determine effective atomic numbers of glass
Using Variable Temperature Powder X-Ray Diffraction to Determine the Thermal Expansion Coefficient of Solid MgO
ERIC Educational Resources Information Center
Corsepius, Nicholas C.; DeVore, Thomas C.; Reisner, Barbara A.; Warnaar, Deborah L.
A laboratory exercise was developed by using variable temperature powder X-ray diffraction (XRD) to determine [alpha] for MgO (periclase)and was tested in the Applied Physical Chemistry and Materials Characterization Laboratories at James Madison University. The experiment which was originally designed to provide undergraduate students with aģ
Gamma ray attenuation coefficient measurement for neutron-absorbent materials
Majid Jalali; Ali Mohammadi
The compounds Na2B4O7, H3BO3, CdCl2 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 1408keV, have been determined
Simultaneous estimation of ultrasonic wave speed, sample thickness, attenuation coefficient, and reflection coefficient
NASA Astrophysics Data System (ADS)
Kinzie, Aaron Wagner
Acoustic wave speed, sample thickness, acoustic attenuation coefficient, and acoustic reflection coefficient are routinely estimated for materials characterization and flaw detection. Previous work at MU yielded a new technique to estimate the wave speed and sample thickness simultaneously. Prior work at MU has also lead to a new approach for simultaneous estimation of attenuation and reflection coefficients given prior knowledge of the sample wave speed and thickness. The research reported in this thesis shows that the simultaneous wave speed and sample thickness estimation technique can be combined with the simultaneous attenuation and reflection coefficient estimation approach. Once the wave speed and Reflection coefficient are estimated the material density can also be estimated. This study shows that without prior knowledge of a sample's properties, it is possible to estimate thickness, acoustic wave speed, acoustic attenuation coefficient, and acoustic reflection coefficient. This is shown theoretically and demonstrated experimentally. The models used are for an isotropic material with a sample of plate type geometry. This is a single sided approach using pulse-echo ultrasonic techniques. The technique utilizes axial scans to find equal diffraction points of interface reflections. The knowledge of the location in the water path length of the equal diffraction points of the interface reflections allows for the estimation of the wave speed and thickness of the sample. Data at the equal diffraction points is then used to calculate the attenuation and reflection coefficients simultaneously. Validity of the combined approach is demonstrated experimentally. Measurement procedures and data processing methods are detailed. Results are given for plastic, copper, and quartz samples. These results are shown with different broadband focused transducers with nominal center frequencies of 5, 10, and 15MHz.
K-shell absorption jump factors and jump ratios in elements between Tm ( Z = 69) and Os ( Z = 76) derived from new mass attenuation coefficient measurements
Necati Kaya; Engin Tirasoglu; G÷khan Apaydin; Volkan Aylikci; Erhan Cengiz
The K-shell absorption jump factors and jump ratios were derived from new mass attenuation coefficients measured using an energy dispersive X-ray fluorescence (EDXRF) spectrometer for Tm, Yb elements being Tm2O3, Yb2O3 compounds and pure Lu, Hf, Ta, W, Re and Os. The measurements, in the region 56¢77keV, were done in a transmission geometry utilizing the K?1, K?2, K?1 and K?2
X-Ray Phase-Contrast Imaging: Phase Reconstructions
Xizeng Wu; Hong Liu
Clinical X-ray imaging has always been based on the biological tissue's differences in X-ray attenuation ever since Roentgen discovered X-ray over 100 years ago. However X-ray-tissue interaction causes X-ray phase changes as well. We have identified the four clinically important factors that affect the X-ray phase visibility in clinical imaging. These factors are: body part attenuation, the spatial coherence of
Electron-Ion Recombination Rate Coefficients and Photoionization Cross Sections for Astrophysically Abundant Elements. V. Relativistic calculations for Fe XXIV and Fe XXV for X-ray modeling
Sultana N. Nahar; Anil K. Pradhan; Hong Lin Zhang
Photoionization and recombination cross sections and rate coefficients are calculated for Li-like Fe XXIV and He-like Fe XXV using the Breit-Pauli R-matrix (BPRM) method. A complete set of total and level-specific parameters is obtained to enable X-ray photoionization and spectral modeling. The ab initio calculations for the unified (e + ion) recombination rate coefficients include both the non-resonant and the resonant recombination (radiative and di-electronic recombination, RR and DR, respectively) for (e + Fe XXV) -> Fe XXIV and (e + Fe XXVI) -> Fe XXV. The level specific rates are computed for all fine structure levels up to n = 10, enabling accurate computation of recombination-cascade matrices and effective rates for the X-ray lines. The total recombination rate coefficients for both Fe XXIV and Fe XXV differ considerably, by several factors, from the sum of RR and DR rates currently used to compute ionization fractions in astrophysical models. As the photoionization/recombination calculations are carried out using an identical eigenfunction expansion, the cross sections for both processes are theoretically self-consistent; the overall uncertainty is estimated to be about 10-20%. All data for Fe XXIV and Fe XXV (and also for H-like Fe XXVI, included for completeness) are available electronically.
Investigations of the attenuation coefficient of a narrow-bandwidth pulsed laser beam in water
Jianhui Bai; Juan Liu; Yi Huang; Yinan Liu; Lu Sun; Dahe Liu; E. S. Fry
The attenuation coefficient of a pulsed laser beam in water is investigated experimentally. It is found that the attenuation coefficient is dependent on the pulse energy and the linewidth of the laser, rather than a constant. The attenuation coefficient for a narrow linewidth laser can exceed that of a broad linewidth laser due to stimulated Brillouin scattering when the laser
Temporal Variations of Seismic Coda: Attenuation-Coefficient View
NASA Astrophysics Data System (ADS)
Morozov, I. B.
When monitoring spatial or temporal variations of the subsurface, it is important to use properties that objectively exist and are insensitive to observational uncertainties. Although the frequency-dependent seismic coda quality factor, Qc is often found to change prior and following relation to major earthquakes and volcanic eruptions, it does not represent such a property. Qc is strongly dependent on the assumed theoretical models, which are usually insufficiently accurate for constraining the actual relationships between the geometrical spreading, anelastic dissipation, and scattering of seismic waves. This inaccuracy often leads to significant exaggeration of attenuation effects, and particularly to interpretations of temporal variations in Qc as related to changes in lithospheric scattering. To overcome this bias, we use an approach based on the temporal attenuation-coefficient, ?(f), instead of Q(f) for describing coda attenuation. Several attenuation case studies suggest that ?(f) typically linearly depends on f, with both the intercept ? = ?(0) and slope d?(f)/df = ?Qe-1 being sensitive to the physical state of the subsurface. Two published examples of temporal variations of local-earthquake coda Q are revisited: non-volcanic (near Stone Canyon in central California) and volcanic (Mt. St. Helens, Washington). In both cases, linear ?(f) patterns are found, with the effects of geometrical spreading (?) on coda attenuation being significantly stronger than those of Qe-1. At Stone Canyon, ? values ranged from 0.035 to 0.06 s-1 and Qe varies from 3000 to 10000, with ? increasing and Qe decreasing during the winter season. At Mt. St. Helens, ? ? 0.18 s-1, and Qe changed from 400 before the eruption to 750 after it. The observed temporal variations are explained by near-surface effects (seasonal variations in the non-volcanic case and gas-, magma-, and geothermal-system related in the volcanic case),which mostly affect the geometrical spreading and anelastic attenuation. Scattering does not appear to be a significant attenuation factor in these areas, or otherwise it may be indistinguishable from the intrinsic attenuation in the data.
X-ray transmissive debris shield
Spielman, R.B.
An X-ray debris shield for use in X-ray lithography that is comprised of an X-ray window having a layer of low density foam exhibits increased longevity without a substantial increase in exposure time. The low density foam layer serves to absorb the debris emitted from the X-ray source and attenuate the shock to the window so as to reduce the chance of breakage. Because the foam is low density, the X-rays are hardly attenuated by the foam and thus the exposure time is not substantially increased.
X-Ray Spectroscopy of Gold Nanoparticles
NASA Astrophysics Data System (ADS)
Nahar, Sultana N.; Montenegro, M.; Pradhan, A. K.; Pitzer, R.
Inner shell transitions, such as 1s-2p, in heavy elements can absorb or produce hard X-rays, and hence are widely used in nanoparticles. Bio-medical research for cancer treatment has been using heavy element nanoparticles, embeded in malignant tumor, for efficient absorption of irradiated X-rays and leading emission of hard X-rays and energetic electrons to kill the surrounding cells. Ejection of a 1s electron during ionization of the element by absorption of a X-ray photon initiates the Auger cascades of emission of photons and electrons. We have investigated gold nanoparticles for the optimal energy range, below the K-edge (1s) ionization threshold, that corresponds to resonant absorption of X-rays with large attenuation coefficients, orders of magnitude higher over the background as well as to that at K-edge threshold. We applied these attenuation coefficients in Monte Carlo simulation to study the intensities of emission of photons and electrons by Auger cascades. The numerical experiments were carried out in a phantom of water cube with a thin layer, 0.1mm/g, of gold nanoparticles 10 cm inside from the surface using the well-known code Geant4. We will present results on photon and electron emission spectra from passing monochromatic X-ray beams at 67 keV, which is the resonant energy for resonant K_{?} lines, at 82 keV, the K-shell ionization threshold, and at 2 MeV where the resonant effect is non-existent. Our findings show a high peak in the gold nanoparticle absorption curve indicating complete absorption of radiation within the gold layer. The photon and electron emission spectra show resonant features. Acknowledgement: Partially supported by a Large Interdisciplinary Grant award of the Ohio State University and NASA APRA program (SNN). The computational work was carried out on the Cray X1 and Itanium 4 cluster at the Ohio Supercomputer Center, Columbus Ohio. "Resonant X-ray Irradiation of High-Z Nanoparticles For Cancer Theranostics" (refereed presentation), A Pradhan, S Nahar, M Montenegro, C Sur, M Mrozik, R Pitzer, E Silver, Y Yu, 50th Annual Meeting of the American Association of Physicists in Medicine in Houston, Texas, July 27 - 31, 2008
X-ray attenuation around K -edge of Zr, Nb, Mo and Pd: A comparative study using proton-induced X-ray emission and 241 Am gamma rays
K. K. Abdullah; K. Karunakaran Nair; N. Ramachandran; K. M. Varier; B. R. S. Babu; Antony Joseph; Rajive Thomas; P. Magudapathy; K. G. M. Nair
Mass attenuation coefficients (Ą\\/?) for Zr, Nb, Mo and Pd elements around their K-edges are measured at 14 energies in the range 15.744¢28.564 keV using secondary excitation from thin Zr, Nb, Mo, Rh, Pd,\\u000a Cd and Sn foils. The measurements were carried out at the K\\u000a \\u000a ?\\u000a and K\\u000a \\u000a ?\\u000a energy values of the target elements by two techniques: (1)
Measurement of Acoustic Attenuation and Absorption Coefficients using Thermometry
NASA Astrophysics Data System (ADS)
Morris, Hugh; Rivens, Ian; Shaw, Adam; ter Haar, Gail
Accurate knowledge of both the attenuation and the absorption coefficient of tissue are required when planning an optimal high intensity focused ultrasound treatment. A novel technique for simple measurement of this parameters has been developed in which a thin-film thermocouple (TFT) is placed between two layers of tissue of different thicknesses. The sample can be rotated about an axis through the junction of the TFT so that it can be insonated from either side leaving the tissue adjacent to the junction unchanged, but changing the overlying thickness. The attenuation and absorption coefficients can be calculated from the heating curves measured in the two orientations. Experiments have been carried out in both tissue mimicking material (TMM) and in ex vivo liver tissue. Weakly focused transducers, resonant at 1.05 MHz, 2.4 MHz and 3.55 MHz were used at free-field spatial peak intensities of 9-14 W/cm2. The temperature rise was measured as a function of time using a TFT. These thermocouples are not subject to the viscous heating artefact that is common to other thermocouple devices and so are advantageous for this purpose. Alignment was achieved with a 3D automated gantry system, which was controlled with specialised software. Timing and data acquisition were also controlled with this software. All experiments were carried out in degassed water. Results for TMM and degassed excised bovine liver are presented.
PET attenuation coefficients from CT images: experimental evaluation of the transformation of CT into PET 511keV attenuation coefficients
C. Burger; G. Goerres; S. Schoenes; A. Buck; A. Lonn; G. von Schulthess
The CT data acquired in combined PET\\/CT studies provide a fast and essentially noiseless source for the correction of photon attenuation in PET emission data. To this end, the CT values relating to attenuation of photons in the range of 40-140 keV must be transformed into linear attenuation coefficients at the PET energy of 511 keV. As attenuation depends on
Measurements of the hard-x-ray reflectivity of iridium
Romaine, S.; Bruni, R.; Gorenstein, P.; Zhong, Z
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.
Infrared Radiography: Modeling X-ray Imaging Without Harmful Radiation
NASA Astrophysics Data System (ADS)
Zietz, Otto; Mylott, Elliot; Widenhorn, Ralf
Planar x-ray imaging is a ubiquitous diagnostic tool and is routinely performed to diagnose conditions as varied as bone fractures and pneumonia. The underlying principle is that the varying attenuation coefficients of air, water, tissue, bone, or metal implants within the body result in non-uniform transmission of x-ray radiation. Through the detection of transmitted radiation, the spatial organization and composition of materials in the body can be ascertained. In this paper, we describe an original apparatus that teaches these concepts by utilizing near infrared radiation and an up-converting phosphorescent screen to safely probe the contents of an opaque enclosure.
Quantitative 3D petrography using x-ray tomography: Application to Bishop Tuff pumice clasts
Guilherme A. R. Gualda; Mark Rivers
Textures are traditionally studied using the petrographic microscope, which limits observations to 2D sections of 3D objects. Given the difficulty in retrieving information on shapes, sizes and spatial distribution of objects in 3D from random sections, a method that can yield observations in 3D is highly desirable.X-ray tomography yields a 3D map of the linear X-ray attenuation coefficient, which is
Erik L. Ritman
Biomedical x-ray imaging has proven to be an indispensable component of many medical diagnostic and treatment techniques. Major technical advances over the years, culminating in helical scanning, multi slice, x-ray computed tomography, can now provide ? 0.5 mm3 resolution 3D images of the spatial distribution of tissue attenuation coefficients of an entire adult human thorax or abdomen. The utility of
Electrical conductivity anomaly and X-ray photoelectron spectroscopy investigation of YCr1-xMnxO3 negative temperature coefficient ceramics
NASA Astrophysics Data System (ADS)
Zhang, Bo; Zhao, Qing; Chang, Aimin; Li, Yiyu; Liu, Yin; Wu, Yiquan
Electrical conductivity anomaly of perovskite-type YCr1-xMnxO3 negative temperature coefficient (NTC) ceramics produced by spark plasma sintering (SPS) has been investigated by using defect chemistry theory combination with X-ray photoelectron spectroscopy (XPS) analysis. From the results of the ln?-1/T curves and the XPS analysis, it can be considered that YCr1-xMnxO3 ceramics exhibit the hopping conductivity. The major carriers in YCrO3 are holes, which are compensated by the oxygen vacancies produced due to the introduction of Mn ions. The Mn4+ ion contents increase monotonically in the range of 0.2 ? x ? 0.5. The resistivity increases at first and then decreases with increasing Mn contents, which has the same varying tendency with activation energy. The electrical conductivity anomaly appearing in these ceramics may be due to the variation of Cr4+ and Mn4+ ions concentration as Mn content changes.
Representative Elementary Length to Measure Soil Mass Attenuation Coefficient
Borges, J. A. R.; Pires, L. F.; Costa, J. C.
With increasing demand for better yield in agricultural areas, soil physical property representative measurements are more and more essential. Nuclear techniques such as computerized tomography (CT) and gamma-ray attenuation (GAT) have been widely employed with this purpose. The soil mass attenuation coefficient (?s) is an important parameter for CT and GAT analysis. When experimentally determined (?es), the use of suitable sized samples enable to evaluate it precisely, as well as to reduce measurement time and costs. This study investigated the representative elementary length (REL) of sandy and clayey soils for ?es measurements. Two radioactive sources were employed (241Am and 137Cs), three collimators (2¢4?mm diameters), and 14 thickness (x) samples (2¢15?cm). Results indicated ideal thickness intervals of 12¢15 and 2¢4?cm for the sources 137Cs and 241Am, respectively. The application of such results in representative elementary area (REA) evaluations in clayey soil clods via CT indicated that ?es average values obtained for x?>?4?cm and source 241Am might induce to the use of samples which are not large enough for soil bulk density evaluations (?s). As a consequence, ?s might be under- or overestimated, generating inaccurate conclusions about the physical quality of the soil under study. PMID:24672338
Representative elementary length to measure soil mass attenuation coefficient.
Borges, J A R; Pires, L F; Costa, J C
With increasing demand for better yield in agricultural areas, soil physical property representative measurements are more and more essential. Nuclear techniques such as computerized tomography (CT) and gamma-ray attenuation (GAT) have been widely employed with this purpose. The soil mass attenuation coefficient (?(s)) is an important parameter for CT and GAT analysis. When experimentally determined (?(es)), the use of suitable sized samples enable to evaluate it precisely, as well as to reduce measurement time and costs. This study investigated the representative elementary length (REL) of sandy and clayey soils for ?(es) measurements. Two radioactive sources were employed ((241)Am and (137)Cs), three collimators (2-4 mm diameters), and 14 thickness (x) samples (2-15 cm). Results indicated ideal thickness intervals of 12-15 and 2-4 cm for the sources (137)Cs and (241)Am, respectively. The application of such results in representative elementary area (REA) evaluations in clayey soil clods via CT indicated that ?(es) average values obtained for x > 4 cm and source (241)Am might induce to the use of samples which are not large enough for soil bulk density evaluations (?(s)). As a consequence, ?(s) might be under- or overestimated, generating inaccurate conclusions about the physical quality of the soil under study. PMID:24672338
Material Identification from X-ray Images Made by Energy-Differentiation Type X-ray Line Sensor
Masao Matsumoto; Naoki Takayama
\\u000a It was confirmed that linear attenuation coefficient and effective atomic number of objects could be identified by X-ray 2D\\u000a and CT images discriminated by different energy. The differences between theoretical and experimental values of linear attenuation\\u000a coefficient of each object from Xray images were 0.01-22.6% for carbon, 0.01%-23.1% for acrylic resin, and 0.07-22.1% for\\u000a aluminum. The effective atomic number of
Natale M. Ceglio; Daniel S. Stearns; Andrew M. Hawryluk; Barbee Jr. Troy W
An x-ray beamsplitter which splits an x-ray beam into two coherent parts by reflecting and transmitting some fraction of an incident beam has applications for x-ray interferometry, x-ray holography, x-ray beam manipulation, and x-ray laser cavity output couplers. The beamsplitter is formed of a wavelength selective multilayer thin film supported by a very thin x-ray transparent membrane. The beamsplitter resonantly
Measurement of the mass attenuation coefficients and electron densities for BiPbSrCaCuO superconductor at different energies
U. Ūevik; H. Baltas
The mass attenuation coefficients for Bi, Pb, Sr, Ca, Cu metals, Bi2O3, PbO, SrCO3, CaO, CuO compounds and solid-state forms of Bi1.7Pb0.3Sr2Ca2Cu3O10 superconductor were determined at 57.5, 65.2, 77.1, 87.3, 94.6, 122 and 136keV energies. The samples were irradiated using a 57Co point source emitted 122 and 136keV ?-ray energies. The X-ray energies were obtained using secondary targets such as
Measurement of mass attenuation coefficients of some boron compounds and the trommel sieve waste in the energy range 15.746¢ 40.930 keV
Orhan ?ńelli; Salih Erzeneo?lu; Recep Boncukńuo?lu
Mass attenuation coefficients of some boron compounds (H3BO3,Na2B4O7 and B3Al2O3) and the trommel sieve waste (TSW) have been measured by using an extremely narrow collimated-beam transmission method in the energy range 15.746¢40.930keV. The characteristic K? and K? X-rays of Zr, Mo, Ag, In, Sb, Ba and Pr passed through H3BO3,Na2B4O7, B3Al2O3 and TSW were detected with a high-resolution Si(Li) detector.
NASA Technical Reports Server (NTRS)
Mccammon, Dan; Cox, D. P.; Kraushaar, W. L.; Sanders, W. T.
The annual progress report on Cosmic X Ray Physics for the period 1 Jan. to 31 Dec. 1990 is presented. Topics studied include: soft x ray background, new sounding rocket payload: x ray calorimeter, and theoretical studies.
Self-compensating x-ray or. gamma. -ray thickness gauge
A gauge is described for determining the mass per unit area, or alternatively the thickness of sheet material by measuring the attenuation, as well as backscatter, of an x-ray beam or the like, while continuously taking into account deviations and changes in localized material composition, insofar as these have an effect on the transmission coefficient of the beam. Electrical signals
A realistic projection simulator for laboratory based X-ray micro-CT
NASA Astrophysics Data System (ADS)
Dhaene, Jelle; Pauwels, Elin; De Schryver, Thomas; De Muynck, Amelie; Dierick, Manuel; Van Hoorebeke, Luc
In X-ray computed tomography (CT) each voxel of the reconstructed image contains a calculated grey value which represents the linear attenuation coefficient for the materials in that voxel. Conventional laboratory based CT scanners use polychromatic X-ray sources and integrating detectors with an energy dependent efficiency. Consequently the reconstructed attenuation coefficients will depend on the spectrum of the source and the spectral sensitivity of the detector. Beam hardening will alter the spectrum significantly as the beam propagates through the sample. Therefore, sample composition and shape will affect the reconstructed attenuation coefficients as well. A polychromatic projection simulator has been developed at the 'Centre for X-ray Tomography' of the Ghent University (UGCT) which takes into account the aforementioned variables, allowing for complete and realistic simulations of CT scans for a wide range of geometrical setups. Monte Carlo simulations of the X-ray tubes and detectors were performed to model their spectral behaviour. In this paper, the implementation and features of the program are discussed. Simulated and real CT scans are compared to demonstrate the quantitative correctness of the simulations. Experiments performed at two different UGCT scanners yield a maximum deviation of 3.9% and 6.5% respectively, between the measured and simulated reconstructed attenuation coefficients.
Electrical conductivity anomaly and X-ray photoelectron spectroscopy investigation of YCr{sub 1?x}Mn{sub x}O{sub 3} negative temperature coefficient ceramics
Zhang, Bo [Key Laboratory of Functional Materials and Devices for Special Environments of CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, Xinjiang Technical Institute of Physics and Chemistry of CAS, Urumqi 830011 (China) [Key Laboratory of Functional Materials and Devices for Special Environments of CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, Xinjiang Technical Institute of Physics and Chemistry of CAS, Urumqi 830011 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Zhao, Qing; Chang, Aimin, E-mail: firstname.lastname@example.com, E-mail: email@example.com [Key Laboratory of Functional Materials and Devices for Special Environments of CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, Xinjiang Technical Institute of Physics and Chemistry of CAS, Urumqi 830011 (China)] [Key Laboratory of Functional Materials and Devices for Special Environments of CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, Xinjiang Technical Institute of Physics and Chemistry of CAS, Urumqi 830011 (China); Li, Yiyu; Liu, Yin; Wu, Yiquan, E-mail: email@example.com, E-mail: email@example.com [Kazuo Inamori School of Engineering, New York State College of Ceramics at Alfred University, Alfred, New York 14802 (United States)] [Kazuo Inamori School of Engineering, New York State College of Ceramics at Alfred University, Alfred, New York 14802 (United States)
Electrical conductivity anomaly of perovskite-type YCr{sub 1?x}Mn{sub x}O{sub 3} negative temperature coefficient (NTC) ceramics produced by spark plasma sintering (SPS) has been investigated by using defect chemistry theory combination with X-ray photoelectron spectroscopy (XPS) analysis. From the results of the ln?-1/T curves and the XPS analysis, it can be considered that YCr{sub 1?x}Mn{sub x}O{sub 3} ceramics exhibit the hopping conductivity. The major carriers in YCrO{sub 3} are holes, which are compensated by the oxygen vacancies produced due to the introduction of Mn ions. The Mn{sup 4+} ion contents increase monotonically in the range of 0.2???x???0.5. The resistivity increases at first and then decreases with increasing Mn contents, which has the same varying tendency with activation energy. The electrical conductivity anomaly appearing in these ceramics may be due to the variation of Cr{sup 4+} and Mn{sup 4+} ions concentration as Mn content changes.
Computer Reconstructed X-Ray Imaging
G. N. Hounsfield
Computed tomography is a method for obtaining a series of radiographic pictures of contiguous slices through a solid object such as the human body. Each picture is computed from a set of X-ray transmission measurements and represents the distribution of X-ray attenuation in the slice. The high sensitivity of the method to changes in both density and atomic number has
Diffraction enhanced x-ray imaging
D. Chapman; W. Thomlinson; R. E. Johnston; D. Washburn; E. Pisano; N. Gm³r; Z. Zhong; R. Menk; F. Arfelli; D. Sayers
Diffraction enhanced imaging is a new x-ray radiographic imaging modality using monochromatic x-rays from a synchrotron which produces images of thick absorbing objects that are almost completely free of scatter. They show dramatically improved contrast over standard imaging applied to the same phantom. The contrast is based not only on attenuation but also the refraction and diffraction properties of the
T. Suresh; Madhubala Talaulikar; Elgar Desa; Antonio Mascaranhas; S. G. Prabhu
Spectral diffuse attenuation Kd(?) is an important apparent optical property that provide information about the attenuation of the spectral downwelling solar irradiance with depth in water. Here we have compared the spectral Kd(?) at ?= 412, 443, 490, 510, 555 and 670 nm derived from the ocean color satellite sensor, SeaWiFS with the in-situ measured values from the Arabian Sea.
X-ray imaging is perhaps the most familiar type of imaging. Images produced by X-rays are due to the different absorption rates of different tissues. Calcium in bones absorbs X-rays the most, so bones look white on a film recording of the X-ray image,
NASA Astrophysics Data System (ADS)
Schroer, Christian G.; Lengeler, Bruno
Due to the weak interaction of hard x-rays with matter it is generally difficult to manipulate x-rays by optical components. As a result, there have been many complementary approaches to making x-ray optics, exploiting refraction, reflection, and diffraction of x-rays by matter. In this chapter, we describe the physics that underly x-ray optics and explain the working principles and performances of a variety of x-ray optics, including refractive x-ray lenses, reflective optics, such as mirrors and waveguides, and diffractive optics,such as multilayer and crystal optics and Fresnel zone plates.
Vaughan, D. (ed.)
A compilation of data is presented. Included are properties of the elements, electron binding energies, characteristic x-ray energies, fluorescence yields for K and L shells, Auger energies, energy levels for hydrogen-, helium-, and neonlike ions, scattering factors and mass absorption coefficients, and transmission bands of selected filters. Also included are selected reprints on scattering processes, x-ray sources, optics, x-ray detectors, and synchrotron radiation facilities. (WRF)
Monitoring changes of optical attenuation coefficients of acupuncture points during laser acupuncture by optical coherence tomography
NASA Astrophysics Data System (ADS)
Huang, Yimei; Yang, Hongqin; Wang, Yuhua; Zheng, Liqin; Xie, Shusen
The physical properties of acupuncture point were important to discover the mechanism of acupuncture meridian. In this paper, we used an optical coherence tomography to monitor in vivo the changes of optical attenuation coefficients of Hegu acupuncture point and non-acupuncture point during laser irradiation on Yangxi acupuncture point. The optical attenuation coefficients of Hegu acupuncture point and non-acupuncture point were obtained by fitting the raw data according to the Beer-Lambert's law. The experimental results showed that the optical attenuation coefficient of Hegu acupuncture point decreased during the laser acupuncture, in contrast to a barely changed result in that of non-acupuncture point. The significant change of optical attenuation coefficient of Hegu acupuncture point indicated that there was a correlation between Hegu and Yangxi acupuncture points to some extent.
NXcom ¢ A program for calculating attenuation coefficients of fast neutrons and gamma-rays
A. M. El-Khayatt
This work is concerned with a construction and use of NXcom computer program for calculating the removal and attenuation coefficients of transmitted fast neutrons and ?-rays, respectively, through mixtures, composites, concretes and compounds. The program uses only one input data file for neutrons and ?-rays calculations. For ?-ray attenuation, the program predictions were tested by comparing them with the well-known
A Precision Measurement of some Attenuation Coefficients for 1.33 MeV Gamma Rays
A-M Roux
Measurements of some mass attenuation coefficients for 1.33 MeV ? radiation of 60Co have been performed in excellent narrow beam collimated geometry. The mass attenuation coefficient of aluminum was determined from the experimental transmission curve with a good accuracy (less than 2 ū 10-3) and the value obtained was then used as a reference for other elements or compounds: copper,
A method to determine the gamma-ray linear attenuation coefficient
C. Celiktas
In this work, gamma-ray linear attenuation coefficients of the materials such as Pb, Fe, Cu and Al were determined by means of traditional energy method and the developed timing detection technique. 1.33MeV-energy radiation emitted from 60Co radioisotope was used in the experiments. The gamma-ray linear attenuation coefficient values of the materials were calculated by using Xcom code, and the experimental
A Precision Measurement of some Attenuation Coefficients for 1.33 MeV Gamma Rays
A.-M. Roux
Measurements of some mass attenuation coefficients for 1.33 MeV gamma radiation of 60Co have been performed in excellent narrow beam collimated geometry. The mass attenuation coefficient of aluminum was determined from the experimental transmission curve with a good accuracy (less than 2 ū 10-3) and the value obtained was then used as a reference for other elements or compounds: copper,
Study of effective atomic numbers and mass attenuation coefficients in some compounds
K. Singh; Rajinderjit Kaur; Vandana Kumar; Vijay Kumar
The effective atomic numbers and mass attenuation coefficients of some different compounds for total and partial photon interactions have been calculated in the energy range 10?2¢105 MeV. The effective atomic numbers and mass attenuation coefficients have also been determined experimentally in the energy range 123¢1132 keV by a transmission method. Experimental and theoretical values are in good agreement. The values
X-ray properties of an anthropomorphic breast phantom for MRI and x-ray imaging.
Freed, Melanie; Badal, Andreu; Jennings, Robert J; de las Heras, Hugo; Myers, Kyle J; Badano, Aldo
The purpose of this study is to characterize the x-ray properties of a dual-modality, anthropomorphic breast phantom whose MRI properties have been previously evaluated. The goal of this phantom is to provide a platform for optimization and standardization of two- and three-dimensional x-ray and MRI breast imaging modalities for the purpose of lesion detection and discrimination. The phantom is constructed using a mixture of lard and egg whites, resulting in a variable, tissue-mimicking structure with separate adipose- and glandular-mimicking components. The phantom can be produced with either a compressed or uncompressed shape. Mass attenuation coefficients of the phantom materials were estimated using elemental compositions from the USDA National Nutrient Database for Standard Reference and the atomic interaction models from the Monte Carlo code PENELOPE and compared with human values from the literature. The image structure was examined quantitatively by calculating and comparing spatial covariance matrices of the phantom and patient mammography images. Finally, a computerized version of the phantom was created by segmenting a computed tomography scan and used to simulate x-ray scatter of the phantom in a mammography geometry. Mass attenuation coefficients of the phantom materials were within 20% and 15% of the values for adipose and glandular tissues, respectively, which is within the estimation error of these values. Matching was improved at higher energies (>20 keV). Tissue structures in the phantom have a size similar to those in the patient data, but are slightly larger on average. Correlations in the patient data appear to be longer than those in the phantom data in the anterior-posterior direction; however, they are within the error bars of the measurement. Simulated scatter-to-primary ratio values of the phantom images were as high as 85% in some areas and were strongly affected by the heterogeneous nature of the phantom. Key physical x-ray properties of the phantom have been quantitatively evaluated and shown to be comparable to those of breast tissue. Since the MRI properties of the phantom have been previously evaluated, we believe it is a useful tool for quantitative evaluation of two- and three-dimensional x-ray and MRI breast imaging modalities for the purpose of lesion detection and characterization. PMID:21606556
ATTENUATION COEFFICIENTS FOR GAMMA RAYS FROM CoŌüČ┬░
S. S. R. Sastry; S. Jnanananda
Attention coefficients in seven different alloys and in Perspex for the ; 1.1715 and 1.3316 Mev gamma radiations from a 17 mc CoŌüČ┬░ source have been ; estimated by the method of least squares, employing the narrow beam geometry of ; Davisson and Evans with provision for accurate collimation. The experimental ; values for the coefficients and the theoretical values,
Illinois at Urbana-Champaign, University of
states that the Langevin radiation pressure on a perfectly absorbing target in an open vessel is 2-PL the speed of sound in the medium (1). Multiplying Langevin radiation pressure by the area of the sound beam. Multiplying that force by the speed of sound yields total acoustic power. Attenuation measurements can be made
Comparison of RNFL thickness and RPE-normalized RNFL attenuation coefficient for glaucoma diagnosis
NASA Astrophysics Data System (ADS)
Vermeer, K. A.; van der Schoot, J.; Lemij, H. G.; de Boer, J. F.
Recently, a method to determine the retinal nerve fiber layer (RNFL) attenuation coefficient, based on normalization on the retinal pigment epithelium, was introduced. In contrast to conventional RNFL thickness measures, this novel measure represents a scattering property of the RNFL tissue. In this paper, we compare the RNFL thickness and the RNFL attenuation coefficient on 10 normal and 8 glaucomatous eyes by analyzing the correlation coefficient and the receiver operator curves (ROCs). The thickness and attenuation coefficient showed moderate correlation (r=0.82). Smaller correlation coefficients were found within normal (r=0.55) and glaucomatous (r=0.48) eyes. The full separation between normal and glaucomatous eyes based on the RNFL attenuation coefficient yielded an area under the ROC (AROC) of 1.0. The AROC for the RNFL thickness was 0.9875. No statistically significant difference between the two measures was found by comparing the AROC. RNFL attenuation coefficients may thus replace current RNFL thickness measurements or be combined with it to improve glaucoma diagnosis.
Mathematical approach to determine the linear attenuation coefficient without collimator in gamma-ray spectrometry.
Kim, Chang-Jong; Cho, Yoon-Hae; Byun, Jong-In; Yun, Ju-Yong
The linear attenuation coefficient is an important factor in the correction of self-attenuation. In this study, a cone beam from a source of ?1 ?Ci was utilised, not equipped with the collimator, and a complete geometric configuration was mathematically modelled. Samples of NaCl, Na2CO3 and (NH4)2SO4 were used to verify the mathematical model. The linear attenuation coefficient can be calculated within ?4 % of difference in the cylindrical sample at energies of 59.5, 121.8, 244.7, 344.2 and 444.0 keV. PMID:23230217
TOTAL ATTENUATION COEFFICIENTS OF 5-11 Mev GAMMA RAYS
The attenuation of neutron-capture gamma rays in Be, Al, Cu, Sn, and ; Pb was measured at energies of 5.44, 6.40, 7.73, and 10.83 Mev. Absorption of ; thermal neutrons frora a reactor by different elements, with the subsequent ; emission of photons, provided the monoenergetic gamma -ray source. An intense ; well-collimated photon beam allowed uncertainties to be held
Abdominal film; X-ray - abdomen; Flat plate; KUB x-ray ... Diagnose a pain in the abdomen or unexplained nausea Identify suspected problems in the urinary system, such as a kidney stone Identify blockage in the intestine Locate ...
Microionization chamber air-kerma calibration coefficients as a function of photon energy for x-ray spectra in the range of 20-250 kVp relative to {sup 60}Co
Snow, J. R.; Micka, J. A.; DeWerd, L. A. [Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53705 (United States)
Purpose: To investigate the applicability of a wide range of microionization chambers for reference dosimetry measurements in low- and medium-energy x-ray beams. Methods: Measurements were performed with six cylindrical microchamber models, as well as one scanning chamber and two Farmer-type chambers for comparison purposes. Air-kerma calibration coefficients were determined at the University of Wisconsin Accredited Dosimetry Calibration Laboratory for each chamber for a range of low- and medium-energy x-ray beams (20-250 kVp), with effective energies ranging from 11.5 keV to 145 keV, and a {sup 60}Co beam. A low-Z proof-of-concept microchamber was developed and calibrated with and without a high-Z silver epoxy on the collecting electrode. Results: All chambers composed of low-Z materials (Z{<=} 13), including the Farmer-type chambers, the scanning chamber, and the PTW TN31014 and the proof-of-concept microchambers, exhibited air-kerma calibration coefficients with little dependence on the quality of the beam. These chambers typically exhibited variations in calibration coefficients of less than 3% with the beam quality, for medium energy beams. However, variations in air-kerma calibration coefficients of greater than 50% were measured over the range of medium-energy x-ray beams for each of the microchambers containing high-Z collecting electrodes (Z > 13). For these high-Z chambers, which include the Exradin A14SL and A16 chambers, the PTW TN31006 chamber, the IBA CC01 chamber, and the proof-of-concept chamber containing silver, the average variation in air-kerma calibration coefficients between any two calibration beams was nearly 25% over the entire range of beam qualities investigated. Conclusions: Due to the strong energy dependence observed with microchambers containing high-Z components, these chambers may not be suitable dosimeters for kilovoltage x-ray applications, as they do not meet the TG-61 requirements. It is recommended that only microchambers containing low-Z materials (Z{<=} 13) be considered for air-kerma calibrations for reference dosimetry in low- and medium-energy x-ray beams.
Modeling spectral diffuse attenuation, absorption, and scattering coefficients in a turbid estuary
Spectral diffuse attenuation coefficients were measured in the Rhode River and Chesapeake Bay, Maryland, on 28 occasions in 1988 and 1989. The model of Kirk was used to extract scattering and absorption coefficients from the measurements in waters considerably more turbid than those in which the model was previously applied. Estimated scattering coefftcients were linearly related to mineral suspended solids.
Paranasal sinus radiography; X-ray - sinuses ... sinus x-ray is taken in a hospital radiology department. Or the x-ray may be taken ... Anslow P. Ear, nose and throat radiology. In: Adam A, Dixon AK, ... Radiology: A Textbook of Medical Imaging . 5th ed. Philadelphia, ...
A Generalised Porosity Formalism for Isotropic and Anisotropic Effective Opacity and Its Effects on X-ray Line Attenuation in Clumped O Star Winds
NASA Technical Reports Server (NTRS)
Sundqvist, Jon O.; Owocki, Stanley P.; Cohen, David H.; Leutenegger, Maurice A.; Townsend, Richard H. D.
We present a generalised formalism for treating the porosity-associated reduction in continuum opacity that occurs when individual clumps in a stochastic medium become optically thick. As in previous work, we concentrate on developing bridging laws between the limits of optically thin and thick clumps. We consider geometries resulting in either isotropic or anisotropic effective opacity, and, in addition to an idealised model in which all clumps have the same local overdensity and scale, we also treat an ensemble of clumps with optical depths set by Markovian statistics. This formalism is then applied to the specific case of bound-free absorption of X- rays in hot star winds, a process not directly affected by clumping in the optically thin limit. We find that the Markov model gives surprisingly similar results to those found previously for the single clump model, suggesting that porous opacity is not very sensitive to details of the assumed clump distribution function. Further, an anisotropic effective opacity favours escape of X-rays emitted in the tangential direction (the venetian blind effect), resulting in a bump of higher flux close to line centre as compared to profiles computed from isotropic porosity models. We demonstrate how this characteristic line shape may be used to diagnose the clump geometry, and we confirm previous results that for optically thick clumping to significantly influence X-ray line profiles, very large porosity lengths, defined as the mean free path between clumps, are required. Moreover, we present the first X-ray line profiles computed directly from line-driven instability simulations using a 3-D patch method, and find that porosity effects from such models also are very small. This further supports the view that porosity has, at most, a marginal effect on X-ray line diagnostics in O stars, and therefore that these diagnostics do indeed provide a good clumping insensitive method for deriving O star mass-loss rates.
A Generalised Porosity Formalism for Isotropic and Anisotropic Effective Opacity and its Effects on X-ray Line Attenuation in Clumped O Star Winds
NASA Technical Reports Server (NTRS)
Sundqvist, Jon O.; Owocki, Stanley P.; Cohen, David H.; Leutenegger, Maurice A.
We present a generalised formalism for treating the porosity-associated reduction in continuum opacity that occurs when individual clumps in a stochastic medium become optically thick. As in previous work, we concentrate on developing bridging laws between the limits of optically thin and thick clumps. We consider geometries resulting in either isotropic or anisotropic effective opacity, and, in addition to an idealised model in which all clumps have the same local overdensity and scale, we also treat an ensemble of clumps with optical depths set by Markovian statistics. This formalism is then applied to the specific case of bound-free absorption of X- rays in hot star winds, a process not directly affected by clumping in the optically thin limit. We find that the Markov model gives surprisingly similar results to those found previously for the single clump model, suggesting that porous opacity is not very sensitive to details of the assumed clump distribution function. Further, an anisotropic effective opacity favours escape of X-rays emitted in the tangential direction (the venetian blind effect), resulting in a bump of higher flux close to line centre as compared to profiles computed from isotropic porosity models. We demonstrate how this characteristic line shape may be used to diagnose the clump geometry, and we confirm previous results that for optically thick clumping to significantly influence X-ray line profiles, very large porosity lengths, defined as the mean free path between clumps, are required. Moreover, we present the first X-ray line profiles computed directly from line-driven instability simulations using a 3-D patch method, and find that porosity effects from such models also are very small. This further supports the view that porosity has, at most, a marginal effect on X-ray line diagnostics in O stars, and therefore that these diagnostics do indeed provide a good clumping insensitive method for deriving O star mass-loss rates.
Stefan Immler; Walter H. G. Lewin
We present a review of X-ray observations of supernovae (SNe). By observing the (~0.1-100 keV) X-ray emission from young SNe, physical key parameters such as the circumstellar matter (CSM) density, mass-loss rate of the progenitor and temperature of the outgoing and reverse shock can be derived as a function of time. Despite intensive search over the last ~25 years, only 15 SNe have been detected in X-rays. We review the individual X-ray observations of these SNe and discuss their implications as to our understanding of the physical processes giving rise to the X-ray emission.
NSDL National Science Digital Library
Neil Fetter
In this activity, learners use simple materials to simulate the effect of X-rays in a safe way. Learners place a piece of window screen over a box and a cardboard pattern on top of the screen. They sprinkle sand over the area of the box. The sand simulates X-rays passing through the screen to the bottom of the box, except where they are blocked by the cardboard. Use this activity to demonstrate how X-rays create an image, including "soft" and shorter wavelength X-rays as well as X-rays from space.
Suppression of Radiation-Induced Testicular Germ Cell Apoptosis by 2,5-Hexanedione Pretreatment. III. Candidate Gene Analysis Identifies a Role for Fas in the Attenuation of X-ray¢Induced Apoptosis
Campion, Sarah N.; Sandrof, Moses A.; Yamasaki, Hideki; Boekelheide, Kim
Germ cell apoptosis directly induced by x-radiation (x-ray) exposure is stage specific, with a higher incidence in stage II/III seminiferous tubules. A priming exposure to the Sertoli cell toxicant 2,5-hexanedione (HD) results in a marked reduction in x-ray¢induced germ cell apoptosis in these affected stages. Because of the stage specificity of these responses, examination of associated gene expression in whole testis tissue has clear limitations. Laser capture microdissection (LCM) of specific cell populations in the testis is a valuable technique for investigating the responses of different cell types following toxicant exposure. LCM coupled with quantitative real-time PCR was performed to examine the expression of apoptosis-related genes at both early (3 h) and later (12 h) time points after x-ray exposure, with or without the priming exposure to HD. The mRNAs examined include Fas, FasL, caspase 3, bcl-2, p53, PUMA, and AEN, which were identified either by literature searches or microarray analysis. Group 1 seminiferous tubules (stages I¢VI) exhibited the greatest changes in gene expression. Further analysis of this stage group (SG) revealed that Fas induction by x-ray is significantly attenuated by HD co-exposure. Selecting only for germ cells from seminiferous tubules of the most sensitive SG has provided further insight into the mechanisms involved in the co-exposure response. It is hypothesized that following co-exposure, germ cells adapt to the lack of Sertoli cell support by reducing the Fas response to normal FasL signals. These findings provide a better understanding and appreciation of the tissue complexity and technical difficulties associated with examining gene expression in the testis. PMID:20616204
Elemental quantification using multiple-energy x-ray absorptiometry
NASA Astrophysics Data System (ADS)
Kozul, N.; Davis, G. R.; Anderson, P.; Elliott, J. C.
A novel implementation of multiple-energy x-ray absorptiometry (MEXA) for elemental quantification has been developed. Species are resolved on the basis of their differential attenuation spectra across a wide energy range, ideally including absorption edges. By measuring the incident and exiting x-ray spectra and using known values of mass attenuation coefficients over selected energy bands, the density line integral of the species along the x-ray path can be calculated from all the selected energy channels simultaneously by non-linear least squares methods. Effects of `escape' peak phenomena are modelled and corrections for them are included in the MEXA software. The applications of MEXA are illustrated by single measurements on aluminium and zirconium foils, quantitation of aqueous KI diffusing into a porous solid, simultaneous measurement of acidic diffusant 0957-0233/10/3/023/img1 and porous solid with which it reacts and which it dissolves and microtomographic reconstructions of liquid and solid specimens containing caesium and/or iodine.
Reconstruction of Ultrasonic Sound Velocity and Attenuation Coefficient Using Linear Arrays: Clinical Assessment
Chen-Han Chang; Sheng-Wen Huang; Hsin-Chia Yang; Yi-Hong Chou; Pai-Chi Li
The aim of this study was to determine the efficacy of using sound velocity and tissue attenuation to clinically discriminate breast cancer from healthy tissues. The methods for reconstructing the sound-velocity and attenuation-coefficient distributions were previously proposed and tested on tissue-mimicking phantoms. The methods require only raw channel data acquired by a linear transducer array and can therefore be implemented
Linear attenuation coefficient and build up factor of MCP-96 alloy for radiation shielding and protection
Deidre Hopkins; Muhammad Maqbool; Mohammed Islam
Build-up factors and linear attenuation coefficients of MCP-96 alloy are determined for radiation shielding and protection, using ^60Co and ^137Cs gamma emitters. A narrow collimated beam of gamma-rays is passed through various thicknesses of MCP-96 alloy and the attenuation in the intensity of the beam is determined. The thickness of the 4 x 4 cm^2 blocks varies from 0.5 cm
IEEE TRANSACTIONSON SONICS ANDULTRASONICS, VOL. SU-32,NO. 2, MARCH 1985 259 Attenuation Coefficient Measurement Technique at
Illinois at Urbana-Champaign, University of
is the ultrasonic attenuation coefficient, which is the de- crease in energy of the sound wavewhenit propagates throughamaterial. The attenuation includes absorption and scattering.Absorption represents the loss of energy
Electron-Ion Recombination Rate Coefficients and Photoionization Cross Sections for Astrophysically Abundant Elements. VII. Relativistic calculations for O VI and O VII for UV and X-ray modeling
Sultana N. Nahar; Anil K. Pradhan
Aimed at ionization balance and spectral analysis of UV and X-ray sources, we present self-consistent sets of photoionization cross sections, recombination cross sections, and rate coefficients for Li-like O VI and He-like O VII. Relativistic fine structure is considered through the Breit-Pauli R-matrix (BPRM) method in the close coupling approximation, implementing the unified treatment for total electron-ion recombination subsuming both radiative and di-electronic recombination processes. Self-consistency is ensured by using an identical wavefunction expansion for the inverse processes of photoionization and photo-recombination. Radiation damping of resonances, important for H-like and He-like core ions, is included. Compared to previous LS coupling results without radiative decay of low-n (cross sections and recombination rates are presented for all fine structure levels n (lSLJ) up to n <= 10, to enable accurate computation of recombination-cascade matrices and spectral formation of prominent UV and X-ray lines such as the 1032,1038 A doublet of O VI, and the `triplet' forbidden, intercombination, and resonance X-ray lines of O VII at 22.1, 21.8, and 21.6 \\ang respectively. Altogether, atomic parameters for 98 levels of O VI and 116 fine structure levels of O VII are theoretically computed. These data should provide a reasonably complete set of photoionization and recombination rates in collisional or radiative equilibrium.
Remote sensing algorithm of particle attenuation coefficient in East China Sea
NASA Astrophysics Data System (ADS)
Bai, Yan; He, Xianqiang; Pan, Delu; Hao, Zengzhou; Song, Qingjun; Lei, Hui
China coastal sea is characteristic of the high concentration of suspended matter which has complex components of mineral particles, organic detritus and phytoplankton, etc. The similarity of spectrum characters of mineral particles and organic particles in backscattering coefficient, and the organic detritus and color dissolve organic matters (CDOM) in absorption coefficient makes the information inverse of coastal ocean color become a very difficult work. In this paper, based on the in situ data of optical investigation in East China Sea in the spring of 2003, including the absorption coefficients of CDOM and de-pigment particles from laboratory spectrophotometer measurement, and the field measurement with ac-9 (WET labs, Inc.), the optical properties of suspended particles were studied. And then, a semi-analysis algorithm of particle attenuation coefficient (Cp) in ECS was developed. There are two key steps in this algorithm, one is the estimation of the ratio of particle backscattering coefficient to the total scattering coefficient; and the other is the retrieval of absorption coefficient of CDOM. With this inversion algorithm of Cp and the input of remote sensing reflectance obtained from the underwater profiler radiometer (Satlantic. Inc.), the particle attenuation coefficient was inversed, which was consistent well with the in situ data of Cp . In the high turbid water, the scattering signal is dominant in the Cp values, so the modeled-Cp was less than the in situ data due to the underestimation of backscattering coefficient in IOPs semi-analysis algorithms. The modeled -Cp at 660nm wavelength has the R2 of 0.84 and RMSE=0.22 compared with the attenuation coefficient at 650nm measured by the ac-9, in which the absorption coefficient of CDOM is neglect. The semi-analysis algorithms of Cp developed in this paper showed a good potential to estimate the biogeochemical parameters, like POC, but the further study should be focused on the distinguish of the sub-division materials with more in situ data set.
NASA Astrophysics Data System (ADS)
Bellazzini, Ronaldo; Costa, Enrico; Matt, Giorgio; Tagliaferri, Gianpiero
1. X-ray polarimetry: historical remarks and other considerations; Part I. Polarimetry Techniques: 2. Scattering polarimetry in high energy astronomy; 3. Photoelectric polarimeters; 4. Bragg crystal polarimeters; 5. X-ray polarimetry with the photon counting pixel detector timepix; 6. HE polarized photon interactions with matter: simulations with geant4; 7. The GPD as a polarimeter: theory and facts; 8. Ideal gas electron multipliers (GEMs) for x-ray polarimeters; 9. Broad-band soft x-ray polarimetry; 10. Feasibility of x-ray photoelectric polarimeters with large field of view; 11. Angular resolution of a photoelectric polarimeter; 12. Development of a Thomson x-ray polarimeter; 13. Hard x / soft gamma ray polarimetry using a Laue lens; Part II. Polarized Emission in X-ray Sources: 14. Probing strong gravity effects with x-ray polarimetry; 15. X-ray polarization from black holes in the thermal state; 16. Strong-gravity effects acting on polarization from orbiting spots; 17. Polarization of thermal emission from accreting black holes; 18. X-ray polarimetry and radio-quiet AGN; 19. The soft x-ray polarization in obscured AGN; 20. The polarization of complex x-ray sources; 21. Polarization of Compton x-rays from jets in AGN; 22. Polarization of x-ray lines from galaxy clusters and elliptical galaxies; 23. Polarization characteristics of rotation-powered pulsars; 24. Polarized x-rays from magnetized neutron stars; 25. Polarization properties of x-ray millisecond pulsars; 26. X-ray polarization signatures of neutron stars; 27. Polarization from the oscillating magnetized accretion torus; 28. X-ray polarization from accreting white dwarfs and associated systems; 29. Polarization of pulsar wind nebulae; 30. X-ray polarization of gamma-ray bursts; 31. Central engine afterglow from GRBs and the polarization signature; 32. GRB afterglow polarimetry. Past, present and future; 33. Gamma-ray polarimetry with SPI; 34. INTEGRAL/IBIS observations of the Crab Nebula and GRB 041219A; 35. Fermi results on the origin of high energy emission in pulsars; 36. Diagnostics of the evolution of spiral galaxies in a cluster environment; Part III. Future Missions: 37. Gravity and extreme magnetism SMEX (GEMS); 38. Programs of x-ray polarimetry in Italy; 39. A polarimeter for IXO; 40. Polarimetry with ASTRO-H soft gamma-ray detector; 41. EXIST and its polarization sensitivity; 42. PoGOLite: a balloon-borne soft gamma-ray polarimeter; 43. Studies of neutron background rejection in the PoGOLite polarimeter; 44. Observing polarized x-rays with PoGOLite; 45. Pre-flight qualification tests of the PoGOLite detector system; 46. The gamma-ray polarimeter experiment (GRAPE) Balloon Payload; 47. POLAR: an instrument dedicated to GRB polarization measurement; 48. Polarisation detection capability of GRIPS; 49. X-ray and y-ray polarimetry small satellite mission polaris; 50. GAP aboard the solar powered sail mission; 51. Hard x-ray polarimeter for small satellite missions; 52. Performance of hard x-ray polarimeter: PHENEX; 53. GRB polarimetry with POET; Index.
Electron-Ion Recombination Rate Coefficients and Photoionization Cross Sections for Astrophysically Abundant Elements. VII. Relativistic calculations for O VI and O VII for UV and X-ray modeling
Sultana N. Nahar; Anil K. Pradhan; Hong Lin Zhang
Aimed at ionization balance and spectral analysis of UV and X-ray sources, we\\u000apresent self-consistent sets of photoionization cross sections, recombination\\u000across sections, and rate coefficients for Li-like O VI and He-like O VII.\\u000aRelativistic fine structure is considered through the Breit-Pauli R-matrix\\u000a(BPRM) method in the close coupling approximation, implementing the unified\\u000atreatment for total electron-ion recombination subsuming both
NASA Technical Reports Server (NTRS)
Satellite X-ray experiments and ground-based programs aimed at observation of X-ray binaries are discussed. Experiments aboard OAO-3, OSO-8, Ariel 5, Uhuru, and Skylab are included along with rocket and ground-based observations. Major topics covered are: Her X-1, Cyg X-3, Cen X-3, Cyg X-1, the transient source A0620-00, other possible X-ray binaries, and plans and prospects for future observational programs.
Linear attenuation coefficient and build up factor of MCP-96 alloy for radiation shielding and protection
NASA Astrophysics Data System (ADS)
Hopkins, Deidre; Maqbool, Muhammad; Islam, Mohammed
Build-up factors and linear attenuation coefficients of MCP-96 alloy are determined for radiation shielding and protection, using ^60Co and ^137Cs gamma emitters. A narrow collimated beam of ?-rays is passed through various thicknesses of MCP-96 alloy and the attenuation in the intensity of the beam is determined. The thickness of the 4 x 4 cm^2 blocks varies from 0.5 cm to 6 cm. Plotting the thickness of the alloy and the corresponding intensity of the beam allowed us to determine its linear attenuation coefficient. The narrow beam geometry is then replaced by broad beam geometry by removing the collimator and the radiation beam is able to interact with the MCP-96 alloy at all possible positions facing the radiation source. Additional radiations obtained by the detector as a result from the scattering of radiation develops the build-up factor. The buildup factor is then calculated using the attenuated beam received by the detector in the broad beam geometry and in the narrow beam geometry. The buildup factor is found to be dependent on the thickness of the MCP-96 attenuator, the beam energy and the source to attenuator distance. These values are providing ways for dose correction in radiation oncology and radiation shielding and protection when MCP-96 is used as tissue compensator or for radiation protection purposes.
Gamma ray attenuation coefficient measurements at 1115, 1173, and 1332 keV
S. Gopal; B. Sanjeevaiah
Gamma ray attenuation coefficients in C, Al, Cu, Zr, Sn and Pb were measured for gamma ray energies 1115, 1173 and 1330 keV using the technique employed earlier by the authors for similar measurements at lower energies. The results will be presented here and discussed.
Two media method for gamma ray attenuation coefficient measurement of archaeological ceramic samples
R. M Cunha e Silva; C. R Appoloni; P. S Parreira; F. R Espinoza-Qui±ones; M. M Coimbra; P. H. A AragŃo
This work reports the application of an alternative methodology for the linear attenuation coefficient determination of irregular shape samples, in such a way that it is not necessary to know the sample thickness. Based on this method, indigenous archaeological ceramic fragments from the region of Londrina, north of Parana State in Brazil, were studied. On the other hand, theoretical mass
Improvements in the two media method for measurements of gamma-ray linear attenuation coefficients
Elimoel A. Elias
The two media method has been previously presented as a solution to the problem of measuring gamma-ray attenuation coefficients of odd-shaped samples. We propose that air is chosen as one of the two media. We theoretically demonstrate that this choice simplifies the equation used, as well as the laboratory work, and also reduces some of the terms associated with experimental
Modeling the vertical distributions of downwelling plane irradiance and diffuse attenuation coefficient in optically deep waters
Xiaoju Pan; Richard C. Zimmerman
The diffuse attenuation coefficient (Kd) is critical to understand the vertical distribution of underwater downwelling irradiance (Ed). Theoretically Ed is composed of the direct solar beam and the diffuse sky irradiance. Applying the statistical results from Hydrolight radiative transfer simulations, Kd is expressed into a mathematical equation (named as PZ06) integrated from the contribution of direct solar beam and diffuse
Total photon attenuation coefficients in some rare earth elements using selective excitation method
NASA Astrophysics Data System (ADS)
SitaMahalakshmi, N. V.; Kareem, M. A.; Premachand, K.
The total mass attenuation coefficients were measured in the elements La, Nd, Sm, Gd and Dy belonging to rare earth region in the energy range 30-55 keV by employing the selective excitation method. This method facilitates selection of excitation energies near the K edge. The present experimental results were compared with the theoretical values due to Chantler and XCOM.
A patient-equivalent attenuation phantom for estimating patient exposures from automatic exposure controlled x-ray examinations of the abdomen and lumbo-sacral spine
Conway, B.J.; Duff, J.E.; Fewell, T.R.; Jennings, R.J.; Rothenberg, L.N.; Fleischman, R.C. (Food and Drug Administration, Rockville, MD (USA))
The Joint Commission on Accreditation of Healthcare Organizations requires diagnostic radiology facilities to known the approximate amount of radiation received by an average patient during radiographic examinations at the facility. Automatic exposure controlled (AEC) techniques are used for many of these exams, and a standard patient-equivalent phantom is necessary when estimating patient exposure on such systems. This is of particular importance if exposures are to be compared among AEC systems with different entrance x-ray spectra. We have developed a phantom, LucA1 Abdomen, to facilitate determining the average patient exposure from AEC anteroposterior (AP) abdomen and lumbo-sacral (LS) spine radiography. The phantom is relatively lightweight, transportable, sturdy, and made of readily available inexpensive materials (Lucite and aluminum). It accurately simulates the primary and scatter transmission through the soft tissue and L-4 spinal regions of a patient-equivalent anthropomorphic phantom for x-ray spectra typically used in abdomen/LS spine radiography. A clinical evaluation to verify the patient-equivalence of three commercial anthropomorphic phantoms (Humanoid, Rando, 3-M) and two acrylic/aluminum phantoms (ANSI and LucA1 Abdomen) has been conducted. The design and development of the LucA1 Abdomen phantom and the evaluation of all phantoms is described.
Experimental spectral measurements of heavy Kedge filtered beams for x-ray computed mammotomography
D J Crotty; R L McKinley; M P Tornai
A dual modality computed mammotomography (CmT) and single photon emission computed tomography (SPECT) system for dedicated 3D breast imaging is in development. Using heavy K-edge filtration, the CmT component narrows the energy spectrum of the cone-shaped x-ray beam incident on the patient's pendant, uncompressed breast. This quasi-monochromatic beam is expected to improve discrimination of tissue with similar attenuation coefficients while
Ceglio, Natale M. (Livermore, CA); Stearns, Daniel S. (Mountain View, CA); Hawryluk, Andrew M. (Modesto, CA); Barbee, Jr., Troy W. (Palo Alto, CA)
An x-ray beamsplitter which splits an x-ray beam into two coherent parts by reflecting and transmitting some fraction of an incident beam has applications for x-ray interferometry, x-ray holography, x-ray beam manipulation, and x-ray laser cavity output couplers. The beamsplitter is formed of a wavelength selective multilayer thin film supported by a very thin x-ray transparent membrane. The beamsplitter resonantly transmits and reflects x-rays through thin film interference effects. A thin film is formed of 5-50 pairs of alternate Mo/Si layers with a period of 20-250 A. The support membrane is 10-200 nm of silicon nitride or boron nitride. The multilayer/support membrane structure is formed across a window in a substrate by first forming the structure on a solid substrate and then forming a window in the substrate to leave a free-standing structure over the window.
R. Rocchia
The observation of X-rays is a relatively new branch of Astronomy. As every new field of science this astronomy had an extremely fast and fruitful development. After twenty years of X ray exploration it is time to summarize the results and to envisage the future. This is the aim of this expose.After a brief review of the birth conditions of
Ceglio, N.M.; Stearns, D.G.; Hawryluk, A.M.; Barbee, T.W. Jr.
An x-ray beamsplitter which splits an x-ray beam into two coherent parts by reflecting and transmitting some fraction of an incident beam has applications for x-ray interferometry, x-ray holography, x-ray beam manipulation, and x-ray laser cavity output couplers. The beamsplitter is formed of a wavelength selective multilayer thin film supported by a very thin x-ray transparent membrane. The beamsplitter resonantly transmits and reflects x-rays through thin film interference effects. A thin film is formed of 5--50 pairs of alternate Mo/Si layers with a period of 20--250 A. The support membrane is 10--200 nm of silicon nitride or boron nitride. The multilayer/support membrane structure is formed across a window in a substrate by first forming the structure on a solid substrate and then forming a window in the substrate to leave a free-standing structure over the window. 6 figs.
... Most experts feel that the benefits of appropriate x-ray imaging greatly outweigh any risks. Young children and babies in the womb are more sensitive to the risks of x-rays. Tell your health care provider if you think ...
Boone, John M. (Folsom, CA); Lane, Stephen M. (Oakland, CA)
A hybrid grid-detector apparatus for x-ray systems wherein a microchannel plate structure has an air-interspaced grid portion and a phosphor/optical fluid-filled grid portion. The grids are defined by multiple adjacent channels separated by lead-glass septa. X-rays entering the air-interspaced grid portion at an angle of impingement upon the septa are attenuated, while non-impinging x-rays pass through to the phosphor/fluid filled portion. X-ray energy is converted to luminescent energy in the phosphor/fluid filled portion and the resultant beams of light are directed out of the phosphor/optical fluid filled portion to an imaging device.
Estimate of attenuation coefficient for ultrasonic tissue characterization using time-varying state-space model.
Shih, L Y; Barnes, C W; Ferrari, L A
The images generated from ultrasound pulse-echo signals have long been used to aid clinical diagnosis. Recently, there has been a growing interest in quantitatively determining the acoustic parameters of the tissue as a means of classification and diagnosis. For example, the frequency-dependent attenuation is known to be correlated with different diseases in the liver. In this paper we introduce a new technique for estimating the attenuation coefficient. The effect of attenuation on an interrogating signal with a gaussian-shaped spectrum can be obtained by studying the Wigner distribution of reflected rf data based on a one-dimensional signal model. We show that under the condition that the attenuation varies linearly with frequency, the spectral mean of the reflected signal decreases linearly with time. The estimation algorithm models the pulse-echo signal as the output of a second-order time-varying state-space innovations model driven by white noise. The state coupling matrix A and the output coupling vector C vary with time in a known fashion; moreover, they are also functions of an unknown constant parameter theta. The attenuation coefficient, which is one of the elements of theta, can be estimated directly using a recursive system identification algorithm. The algorithm was verified using both computer-generated synthetic data and in-vivo liver data of known diagnosis. The results show correlation between the estimated parameter and the pathological state of the tissue. PMID:3057715
Determination of attenuation coefficient for self-absorption correction in routine gamma ray spectrometry of environmental bulk sample
K. Satoh; N. Ohashi; H. Higuchi; M. Noguchi
A simple method to determine -ray attenuation coefficients using Ba-133 -rays has been developed and applied to self-absorption correction in routine -ray spectrometry for environmental samples composed of unknown matrix elements. Experimental values of the mass attenuation coefficient obtained by the method agree well with calculated values for samples of known elemental composition which was determined by means of chemical
Vertebral radiography; X-ray - spine; Thoracic x-ray; Spine x-ray; Thoracic spine films; Back films ... The test is done in a hospital radiology department or in the health care provider's office. You will lie on the x-ray table in different positions. If the x-ray ...
Quantitative RNFL attenuation coefficient measurements by RPE-normalized OCT data
NASA Astrophysics Data System (ADS)
Vermeer, K. A.; van der Schoot, J.; Lemij, H. G.; de Boer, J. F.
We demonstrate significantly different scattering coefficients of the retinal nerve fiber layer (RNFL) between normal and glaucoma subjects. In clinical care, SD-OCT is routinely used to assess the RNFL thickness for glaucoma management. In this way, the full OCT data set is conveniently reduced to an easy to interpret output, matching results from older (non- OCT) instruments. However, OCT provides more data, such as the signal strength itself, which is due to backscattering in the retinal layers. For quantitative analysis, this signal should be normalized to adjust for local differences in the intensity of the beam that reaches the retina. In this paper, we introduce a model that relates the OCT signal to the attenuation coefficient of the tissue. The average RNFL signal (within an A-line) was then normalized based on the observed RPE signal, resulting in normalized RNFL attenuation coefficient maps. These maps showed local defects matching those found in thickness data. The average (normalized) RNFL attenuation coefficient of a fixed band around the optic nerve head was significantly lower in glaucomatous eyes than in normal eyes (3.0mm-1 vs. 4.9mm-1, P<0.01, Mann-Whitney test).
... x-rays. top of page What does the equipment look like? A panoramic x-ray machine consists ... current x-ray images for diagnosis and disease management. The digital format also allows the dentist to ...
Outstanding X-ray shielding effects of carbon nanotubes Toshihiko Fujimori1, Shuji Tsuruoka1, Bunshi Fugetsu2, Shigeo Maruyama3, Akihiko
Maruyama, Shigeo
1 Outstanding X-ray shielding effects of carbon nanotubes Toshihiko Fujimori1, Shuji Tsuruoka1 by carbon nanotubes (CNTs). We observed that the mass attenuation coefficient of CNTs was significantly higher (> 100%) than that observed for highly oriented pyrolytic graphite (HOPG) and fullerenes (C60
Hard x-ray nanofocusing with refractive x-ray optics: full beam characterization by ptychographic imaging
NASA Astrophysics Data System (ADS)
Schroer, Christian G.; Brack, Florian-Emanuel; Brendler, Roman; H÷nig, Susanne; Hoppe, Robert; Patommel, Jens; Ritter, Stephan; Scholz, Maria; Schropp, Andreas; Seiboth, Frank; Nilsson, Daniel; Rahomõki, Jussi; Uhlķn, Fredrik; Vogt, Ulrich; Reinhardt, Juliane; Falkenberg, Gerald
Hard x-ray scanning microscopy relies on small and intensive nanobeams. Refractive x-ray lenses are well suited to generate hard x-ray beams with lateral dimensions of 100 nm and below. The diffraction limited beam size of refractive x-ray lenses mainly depends on the focal length and the attenuation inside the lens material. The numerical aperture of refractive lenses scales with the inverse square root of the focal length until it reaches the critical angle of total reflection. We have used nanofocusing refractive x-ray lenses made of silicon to focus hard x-rays at 8 and 20 keV to (sub-)100 nm dimensions. Using ptychographic scanning coherent diffraction imaging we have characterized these nanobeams with high accuracy and sensitivity, measuring the full complex wave field in the focus. This gives access to the full caustic and aberrations of the x-ray optics.
ERIC Educational Resources Information Center
Smith, D. K.; Smith, K. L.
Reviews applications in research and analytical characterization of compounds and materials in the field of X-ray diffraction, emphasizing new developments in applications and instrumentation in both single crystal and powder diffraction. Cites 414 references. (CS)
NSDL National Science Digital Library
This site from the University of London presents a tutorial on several methods of X-ray diffraction, including the powder, rotating crystal, and Laue methods Each section includes interactive Java applets, exercises, and links to a glossary of terms.
Effective recombination coefficient and solar zenith angle effects on low-latitude D-region ionosphere evaluated from VLF signal amplitude and its time delay during X-ray solar flares
NASA Astrophysics Data System (ADS)
Basak, Tamal; Chakrabarti, Sandip Kumar
Excess solar X-ray radiation during solar flares causes an enhancement of ionization in the ionospheric D-region and hence affects sub-ionospherically propagating VLF signal amplitude and phase. VLF signal amplitude perturbation (DeltaA) and amplitude time delay (Deltat) (vis- ┤a-vis corresponding X-ray light curve as measured by GOES-15) of NWC/19.8 kHz signal have been computed for solar flares which is detected by us during Jan-Sep 2011. The signal is recorded by SoftPAL facility of IERC/ICSP, Sitapur (22(░) 27'N, 87(░) 45'E), West Bengal, India. In first part of the work, using the well known LWPC technique, we simulated the flare induced excess lower ionospheric electron density by amplitude perturbation method. Unperturbed D-region electron density is also obtained from simulation and compared with IRI-model results. Using these simulation results and time delay as key parameters, we calculate the effective electron recombination coefficient (alpha_{eff}) at solar flare peak region. Our results match with the same obtained by other established models. In the second part, we dealt with the solar zenith angle effect on D-region during flares. We relate this VLF data with the solar X-ray data. We find that the peak of the VLF amplitude occurs later than the time of the X-ray peak for each flare. We investigate this so-called time delay (Deltat). For the C-class flares we find that there is a direct correspondence between Deltat of a solar flare and the average solar zenith angle Z over the signal propagation path at flare occurrence time. Now for deeper analysis, we compute the Deltat for different local diurnal time slots DT. We find that while the time delay is anti-correlated with the flare peak energy flux phi_{max} independent of these time slots, the goodness of fit, as measured by reduced-chi(2) , actually worsens as the day progresses. The variation of the Z dependence of reduced-chi(2) seems to follow the variation of standard deviation of Z along the T_x-R_x propagation path. In other words, for the flares having almost constant Z over the path a tighter anti-correlation between Deltat and phi_{max} was observed.
Effective recombination coefficient and solar zenith angle effects on low-latitude D-region ionosphere evaluated from VLF signal amplitude and its time delay during X-ray solar flares
NASA Astrophysics Data System (ADS)
Basak, Tamal; Chakrabarti, Sandip K.
Excess solar X-ray radiation during solar flares causes an enhancement of ionization in the ionospheric D-region and hence affects sub-ionospherically propagating VLF signal amplitude and phase. VLF signal amplitude perturbation (? A) and amplitude time delay (? t) (vis-ß-vis corresponding X-ray light curve as measured by GOES-15) of NWC/19.8 kHz signal have been computed for solar flares which is detected by us during Jan-Sep 2011. The signal is recorded by SoftPAL facility of IERC/ICSP, Sitapur (22? 27'N, 87? 45'E), West Bengal, India. In first part of the work, using the well known LWPC technique, we simulated the flare induced excess lower ionospheric electron density by amplitude perturbation method. Unperturbed D-region electron density is also obtained from simulation and compared with IRI-model results. Using these simulation results and time delay as key parameters, we calculate the effective electron recombination coefficient ( ? eff ) at solar flare peak region. Our results match with the same obtained by other established models. In the second part, we dealt with the solar zenith angle effect on D-region during flares. We relate this VLF data with the solar X-ray data. We find that the peak of the VLF amplitude occurs later than the time of the X-ray peak for each flare. We investigate this so-called time delay (? t). For the C-class flares we find that there is a direct correspondence between ? t of a solar flare and the average solar zenith angle Z over the signal propagation path at flare occurrence time. Now for deeper analysis, we compute the ? t for different local diurnal time slots DT. We find that while the time delay is anti-correlated with the flare peak energy flux ? max independent of these time slots, the goodness of fit, as measured by reduced- ? 2, actually worsens as the day progresses. The variation of the Z dependence of reduced- ? 2 seems to follow the variation of standard deviation of Z along the T x - R x propagation path. In other words, for the flares having almost constant Z over the path a tighter anti-correlation between ? t and ? max was observed.
NASA Technical Reports Server (NTRS)
Mccammon, Dan; Cox, D. P.; Kraushaar, W. L.; Sanders, W. T.
This final report covers the period 1 January 1985 - 31 March 1992. It is divided into the following sections: the soft x-ray background; proportional counter and filter calibrations; sounding rocket flight preparations; new sounding rocket payload: x-ray calorimeter; and theoretical studies. Staff, publications, conference proceedings, invited talks, contributed talks, colloquia and seminars, public service lectures, and Ph. D. theses are listed.
Total attenuation coefficient of intralipid dilutions for discrete laser wavelengths between 405 and 1315 nm
NASA Astrophysics Data System (ADS)
Dreischuh, Tanja N.; Gurdev, Ljuan L.; Vankov, Orlin I.; Avramov, Lachezar A.; Stoyanov, Dimitar V.
The experimental investigations on different aspects of optical tomography require the knowledge of the optical parameters of tissues and tissue-like phantoms in order to unambiguously interpret the experimental data and specify characteristic inhomogeneities in tissue diagnostics. The main optical parameters of interest are the absorption coefficient, the scattering, backscattering, and reduced-scattering coefficients, the total attenuation (extinction) coefficient and the anisotropy factor. In this work, we extend our investigations of the optical properties of tissuemimicking phantoms, such as Intralipid-20% fat emulsion, using an approach we have developed recently based on the peculiarities of laser radiation beams propagating through semi-infinite turbid media. The dependence of the total attenuation coefficient on the Intralipid concentration, for laser radiation wavelengths ?=405, 672, 850, and 1314 nm, is studied, by using a set of phantoms consisting of different dilutions of Intralipid in distilled water. The experimental results for the extinction are in agreement with our previous results and with empiric formulae found by other authors concerning the wavelength dependence of the scattering coefficient of Intralipid -10% and Intralipid - 20%. They are also in agreement with known data of the water absorptance. As a whole, the results obtained in this work confirm the consideration of the experimental phantoms as semi-infinite media. They also confirm and extend theoretical and experimental results obtained previously, and reveal advantages of using longer wavelengths for deeper diagnostics of tissues and mimic turbid media.
Measurement of photon mass attenuation coefficients of plutonium from 60 to 2615 keV
M. Rettschlag; R. Berndt; P. Mortreau
Measurements have been made to determine plutonium photon mass attenuation coefficients by using a collimated-beam transmission method in the energy range from 60 to 2615keV. These experimental results were compared with previous experimental and theoretical data. Good agreements are observed in the 240¢800keV energy range, whereas differences up to maximum 10% are observed out of these limits.
Comparison of measured and satellite-derived spectral diffuse attenuation coefficients for the Arabian Sea
Suresh Thayapurath; Madhubala Talaulikar; Elgar Desa; S. G. P. Matondkar; Antonio Mascarenhas
We present here the results of our study comparing the spectral diffuse attenuation coefficients Kd(?) measured in the Arabian Sea with those derived from the Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) using three algorithms, of which two are empirical-data-driven and one is semi-analytical. The measurements were carried out in all water types and the mean values of the measured spectral Kd(?)
Gamma-ray attenuation coefficients of some building materials available in Egypt
M. E. Medhat
Mass attenuation coefficients of various types of building materials were measured using a high-resolution HPGe spectrometer detector. Samples were irradiated by gamma-rays emitted from point sources of 241Am, 133Ba, 60Co and 137Cs. The results are in good agreement with the theoretical calculations of XCOM code. The effectiveness of building materials in shielding were determined over the range 50¢3000keV. Finally, the
Diffuse attenuation coefficient of downwelling irradiance: An evaluation of remote sensing methods
Zhong-Ping Lee; Miroslaw Darecki; Kendall L. Carder; Curtiss O. Davis; Dariusz Stramski; W. Joseph Rhea
The propagation of downwelling irradiance at wavelength ? from surface to a depth (z) in the ocean is governed by the diffuse attenuation coefficient, $\\\\bar{K}_{d}$(?). There are two standard methods for the derivation of $\\\\bar{K}_{d}$(?) in remote sensing, which both are based on empirical relationships involving the blue-to-green ratio of ocean color. Recently, a semianalytical method to derive $\\\\bar{K}_{d}$(?) from
Obtaining flat x-ray images from round objects
Technology Transfer Automated Retrieval System (TEKTRAN)
A technique to correct deficiencies in x-ray images of cylindrical or spherical objects that are a consequence of the geometry of the sample is derived, for both two-dimensional (2D) and linescan imaging. The methods described involve the use of attenuators specifically shaped to equalize the x-ray ...
Magnified hard x-ray image in one dimension
Britten, James [Department of Chemistry, McMaster University, Hamilton, Ontario L8S4L8 (Canada); Feng Zhechuan [Department of Electrical Engineering, National Taiwan University, Taipei 106-17, Taiwan (China); Xu Gu [Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario L8S4L7 (Canada)
The possibility of magnified x-ray imaging is explored, by the near-field attenuation of a sample intercepting a spherical wave-front, plus the beam profile modulation by Borrmann pyramid based on dynamic x-ray scattering. It is verified by experiments in one dimension as well as numerical simulation.
Abnormal breast tissue imaging based on multi-energy x-ray
NASA Astrophysics Data System (ADS)
Kang, Dong-Goo; Han, Seok-Min; Sung, Younghun; Lee, SeongDeok
The dual or multi-energy x-ray technique facilitates to generate tissue-selective images, by exploiting tissue-specific energy dependence of x-ray attenuation. An abnormal breast is considered to be a mixture of adipose, glandular, and abnormal tissues, but three tissues cannot be selectively decomposed because the total attenuation of a tissue is represented by only two attenuation basis functions at diagnostic energy range. This paper presents a novel method to selectively represent abnormal breast tissue, using polyenergetic multi-energy x-ray. We show that an abnormal tissue can be revealed from the total thickness map, which is virtually constructed by assuming a healthy and compressed breast. Specifically, regression analysis is first performed using the multi-energy images of the prepared calibration phantom that consists of two basis materials. Total thickness map is then constructed by linearly combining thickness maps of basis materials, where the optimal weights for combination are determined so that the uniformity of total breast thickness is maximized. It is noted that the proposed method does not need accurate attenuation coefficients of breast tissues. Simulation results show that the proposed method dramatically improves the detectability of mass that is obscured by normal structures.
Observations of the vertical structure of the diffuse attenuation coefficient spectrum
NASA Astrophysics Data System (ADS)
Siegel, D. A.; Dickey, T. D.
Profiles of the diffuse attenuation coefficient spectrum for downwelling spectral irradiance ( Kd( z, ?)) were determined using data taken during the autumn of 1982 in the eastern North Pacific Ocean as part of the Optical Dynamics Experiment (ODEX). The near-surface Kd(5 m, ?) was consistent with Jerlov water types IA or IB and did not show any significant variations with sun altitude angle or cloud amount, supporting the notion that Kd( z, ?) is a "quasi-inherent" optical property. Vertical profiles of Kd( z, ?) showed significant structures with amplitudes that decrease with increasing wavelength. The observed depth-wavelength distribution may be divided into a blue-green group (400-500 nm) with a vertical structure similar to the vertical distribution of chlorophyll pigments and a green-yellow group (500-575 nm) with little vertical variation. For wavelengths >575 nm, the values of Kd( z, ?) decreased with depth apparently because of limitations of the irradiance sensors. The mean vertical distribution of Kd( z, ?) for the blue-green group was well-correlated with the mean in situ fluorescence (correlation coefficient r ś 0.94-0.99) and with the mean total pigment concentration ( r ś 0.90-0.95). The correlation coefficients relating Kd( z, ?) with the phaeopigment concentration ( r ś 0.84-0.92) were higher than those relating the chlorophyll a concentration ( r ś 0.63-0.90), indicating the contributions of detrital materials. The mean beam attenuation coefficient at 660 nm was not significantly correlated with Kd( z, ?). The total pigment specific diffuse attenuation coefficient spectrum was similar to spectra determined from previous studies, with departures only in the blue region of the spectrum ( ? < 440 nm). The differences may be attributed to detrital effects.
Electron-Ion Recombination Rate Coefficients and Photoionization Cross Sections for Astrophysically Abundant Elements. VII. Relativistic calculations for O VI and O VII for UV and X-ray modeling
Nahar, S N; Nahar, Sultana N.; Pradhan, Anil K.
Aimed at ionization balance and spectral analysis of UV and X-ray sources, we present self-consistent sets of photoionization cross sections, recombination cross sections, and rate coefficients for Li-like O VI and He-like O VII. Relativistic fine structure is considered through the Breit-Pauli R-matrix (BPRM) method in the close coupling approximation, implementing the unified treatment for total electron-ion recombination subsuming both radiative and di-electronic recombination processes. Self-consistency is ensured by using an identical wavefunction expansion for the inverse processes of photoionization and photo-recombination. Radiation damping of resonances, important for H-like and He-like core ions, is included. Compared to previous LS coupling results without radiative decay of low-n (cross sections and recombination rate...
Phase contrast imaging using a micro focus x-ray source
NASA Astrophysics Data System (ADS)
Zhou, Wei; Majidi, Keivan; Brankov, Jovan G.
Phase contrast x-ray imaging, a new technique to increase the imaging contrast for the tissues with close attenuation coefficients, has been studied since mid 1990s. This technique reveals the possibility to show the clear details of the soft tissues and tumors in small scale resolution. A compact and low cost phase contrast imaging system using a conventional x-ray source is described in this paper. Using the conventional x-ray source is of great importance, because it provides the possibility to use the method in hospitals and clinical offices. Simple materials and components are used in the setup to keep the cost in a reasonable and affordable range.Tungsten K?1 line with the photon energy 59.3 keV was used for imaging. Some of the system design details are discussed. The method that was used to stabilize the system is introduced. A chicken thigh bone tissue sample was used for imaging followed by the image quality, image acquisition time and the potential clinical application discussion. High energy x-ray beam can be used in phase contrast imaging. Therefore the radiation dose to the patients can be greatly decreased compared to the traditional x-ray radiography.
Gamma-ray attenuation coefficients in some heavy metal oxide borate glasses at 662 keV
A. Khanna; S. S. Bhatti; K. J. Singh; K. S. Thind
The linear attenuation coefficient (mu) and mass attenuation coefficients (mu\\/rho) of glasses in three systems: xPbO(1-x)B2O3, 0.25PbO.xCdO(0.75-x)B2O3 and xBi2O3(1-x)B2O3 were measured at 662 keV. Appreciable variations were noted in the attenuation coefficients due to changes in the chemical composition of glasses. In addition to this, absorption cross-sections per atom were also calculated. A comparison of shielding properties of these glasses
Gamma-ray attenuation coefficients in some heavy metal oxide borate glasses at 662 keV
Atul Khanna; S. S. Bhatti; K. J. Singh; K. S. Thind
The linear attenuation coefficient (?) and mass attenuation coefficients (??) of glasses in three systems: xPbO(1 ? x)B2O3, 0.25PbO Ę xCdO(0.75 ? x)B2O3 and xBi2O3(1 ? x)B2O3 were measured at 662 keV. Appreciable variations were noted in the attenuation coefficients due to changes in the chemical composition of glasses. In addition to this, absorption cross-sections per atom were also calculated.
X-ray radiography for container inspection
Katz, Jonathan I. (Clayton, MO); Morris, Christopher L. (Los Alamos, NM)
Arrangements of X-ray inspection systems are described for inspecting high-z materials in voluminous objects such as containers. Inspection methods may involve generating a radiographic image based on detected attenuation corresponding to a pulsed beams of radiation transmitted through a voluminous object. The pulsed beams of radiation are generated by a high-energy source and transmitted substantially downward along an incident angle, of approximately 1.degree. to 30.degree., to a vertical axis extending through the voluminous object. The generated radiographic image may be analyzed to detect on localized high attenuation representative of high-z materials and to discriminate high-z materials from lower and intermediate-z materials on the basis of the high density and greater attenuation of high-z material for higher energy (3-10 MeV) X-rays, and the compact nature of threatening masses of fissionable materials.
... is useful when the dentist does not have a panoramic X-ray machine or when the child has difficulty in taking bitewing or periapical X-rays. Orthodontic X-rays (also called cephalometric or lateral skull) Ś This type of X-ray shows the head from the side. It is used to evaluate growth of the jaws ...
X-ray - lumbosacral spine; X-ray - lower spine ... be placed over the lower part of your spine. You will be asked to hold your breath ... x-ray. The most common reason for lumbosacral spine x-ray is to look for the cause ...
Simultaneous reconstruction of emission activity and attenuation coefficient distribution from TOF data, acquired with external transmission source
NASA Astrophysics Data System (ADS)
Panin, V. Y.; Aykac, M.; Casey, M. E.
The simultaneous PET data reconstruction of emission activity and attenuation coefficient distribution is presented, where the attenuation image is constrained by exploiting an external transmission source. Data are acquired in time-of-flight (TOF) mode, allowing in principle for separation of emission and transmission data. Nevertheless, here all data are reconstructed at once, eliminating the need to trace the position of the transmission source in sinogram space. Contamination of emission data by the transmission source and vice versa is naturally modeled. Attenuated emission activity data also provide additional information about object attenuation coefficient values. The algorithm alternates between attenuation and emission activity image updates. We also proposed a method of estimation of spatial scatter distribution from the transmission source by incorporating knowledge about the expected range of attenuation map values. The reconstruction of experimental data from the Siemens mCT scanner suggests that simultaneous reconstruction improves attenuation map image quality, as compared to when data are separated. In the presented example, the attenuation map image noise was reduced and non-uniformity artifacts that occurred due to scatter estimation were suppressed. On the other hand, the use of transmission data stabilizes attenuation coefficient distribution reconstruction from TOF emission data alone. The example of improving emission images by refining a CT-based patient attenuation map is presented, revealing potential benefits of simultaneous CT and PET data reconstruction.
NASA Astrophysics Data System (ADS)
Cavalieri, A. L.; Fritz, D. M.; Lee, S. H.; Bucksbaum, P. H.; Reis, D. A.; Rudati, J.; Mills, D. M.; Fuoss, P. H.; Stephenson, G. B.; Kao, C. C.; Siddons, D. P.; Lowney, D. P.; Macphee, A. G.; Weinstein, D.; Falcone, R. W.; Pahl, R.; Als-Nielsen, J.; Blome, C.; D³sterer, S.; Ischebeck, R.; Schlarb, H.; Schulte-Schrepping, H.; Tschentscher, Th.; Schneider, J.; Hignette, O.; Sette, F.; Sokolowski-Tinten, K.; Chapman, H. N.; Lee, R. W.; Hansen, T. N.; Synnergren, O.; Larsson, J.; Techert, S.; Sheppard, J.; Wark, J. S.; Bergh, M.; Caleman, C.; Huldt, G.; van der Spoel, D.; Timneanu, N.; Hajdu, J.; Akre, R. A.; Bong, E.; Emma, P.; Krejcik, P.; Arthur, J.; Brennan, S.; Gaffney, K. J.; Lindenberg, A. M.; Luening, K.; Hastings, J. B.
Linear-accelerator-based sources will revolutionize ultrafast x-ray science due to their unprecedented brightness and short pulse duration. However, time-resolved studies at the resolution of the x-ray pulse duration are hampered by the inability to precisely synchronize an external laser to the accelerator. At the Sub-Picosecond Pulse Source at the Stanford Linear-Accelerator Center we solved this problem by measuring the arrival time of each high energy electron bunch with electro-optic sampling. This measurement indirectly determined the arrival time of each x-ray pulse relative to an external pump laser pulse with a time resolution of better than 60 fs rms.
NSDL National Science Digital Library
In this activity, by the Concord Consortium's Molecular Literacy project, students are introduced to the fundamental principles of X-ray crystallography and "guides students through a series of activities for learning how structural information can be derived from X-ray diffraction patterns." Upon completion of this activity students should be able to describe what can be detected with X-ray crystallography (proteins in particular) and explain the impact of temperature, atom size, and impurities in the test. The activity itself is a java-based interactive resource built upon the free, open source Molecular Workbench software. In the activity, students are allowed to explore at their own pace in a digital environment full of demonstrations, illustrations, and models they can manipulate. In addition to the activity, visitors will find an overview of the activity, a test and rubric, central concepts, and their correlation to AAAS standards.
X-ray astronomical spectroscopy
NASA Technical Reports Server (NTRS)
Holt, Stephen S.
The contributions of the Goddard group to the history of X-ray astronomy are numerous and varied. One role that the group has continued to play involves the pursuit of techniques for the measurement and interpretation of the X-ray spectra of cosmic sources. The latest development is the selection of the X-ray microcalorimeter for the Advanced X-ray Astrophysics Facility (AXAF) study payload. This technology is likely to revolutionize the study of cosmic X-ray spectra.
Landis, Eric N., E-mail: firstname.lastname@example.com [Department of Civil and Environmental Engineering, University of Maine, 5711 Boardman Hall, Orono, Maine 04469 (United States); Keane, Denis T., E-mail: email@example.com [Department of Materials Science and Engineering, Northwestern University (United States); DND-CAT, Advanced Photon Source, Argonne National Laboratory, Bldg. 432/A002, 9700 S. Cass Ave, Argonne, Illinois 60439 (United States)
In this tutorial, we describe X-ray microtomography as a technique to nondestructively characterize material microstructure in three dimensions at a micron level spatial resolution. While commercially available laboratory scale instrumentation is available, we focus our attention on synchrotron-based systems, where we can exploit a high flux, monochromatic X-ray beam to produce high fidelity three-dimensional images. A brief description of the physics and the mathematical analysis behind the technique is followed by example applications to specific materials characterization problems, with a particular focus on the utilization of three-dimensional image processing that can be used to extract a wide range of useful information.
X-ray laser driven gold targets
Petrova, Tz. B., E-mail: email@example.com; Whitney, K. G.; Davis, J. [Plasma Physics Division, Naval Research Laboratory, 4555 Overlook Ave. SW, Washington, DC 20375 (United States)] [Plasma Physics Division, Naval Research Laboratory, 4555 Overlook Ave. SW, Washington, DC 20375 (United States)
The femtosecond population dynamics of gold irradiated by a coherent high-intensity (>10{sup 17}?W/cm{sup 2}) x-ray laser pulse is investigated theoretically. There are two aspects to the assembled model. One is the construction of a detailed model of platinum-like gold inclusive of all inner-shell states that are created by photoionization of atomic gold and decay either by radiative or Auger processes. Second is the computation of the population dynamics that ensues when an x-ray pulse is absorbed in gold. The hole state generation depends on the intensity and wavelength of the driving x-ray pulse. The excited state populations reached during a few femtosecond timescales are high enough to generate population inversions, whose gain coefficients are calculated. These amplified lines in the emitted x-ray spectrum provide important diagnostics of the radiation dynamics and also suggest a nonlinear way to increase the frequency of the coherent output x-ray pulses relative to the frequency of the driver input x-ray pulse.
Modeling X-Ray Photoionized Plasmas: Ion Storage Ring Measurements of Low Temperature Dielectronic Recombination Rate Coefficients for L-Shell Iron
NASA Technical Reports Server (NTRS)
Savin, D. W.; Badnell, N. R.; Bartsch, T.; Brandau, C.; Chen, M. H.; Grieser, M.; Gwinner, G.; Hoffknecht, A.; Kahn, S. M.; Linkemann, J.
Iron L-shell ions (Fe XVII to Fe XXIV) play an important role in determining the line emission and thermal and ionization structures of photoionized gases. Existing uncertainties in the theoretical low temperature dielectronic recombination (DR) rate coefficients for these ions significantly affects our ability to model and interpret observations of photoionized plasmas. To help address this issue, we have initiated a laboratory program to produce reliable low temperature DR rates. Here, we present some of our recent results and discuss some of their astrophysical implications.
Determination of Mass Attenuation Coefficients for CuInSe2 and CuGaSe2 Semiconductors
Emin Bacaksiz
This work presents mass attenuation coefficients values of CuInSe2 and CuGaSe2 semiconductor thin films commonly used in photovoltaic devices. The mass attenuation coefficients were measured at different energies from 11.9 to 37.3 keV by using the secondary excitation method. Monochromatic photons were obtained using the Br, Sr, Mo, Cd, Te, Ba and Nd secondary targets. 59.5 keV gamma rays emitted
Retrieval of diffuse attenuation coefficient in the Chesapeake Bay and turbid ocean regions for satellite ocean color applications
Menghua Wang; SeungHyun Son; Lawrence W. Harding Jr
There are several empirical and semianalytical models for the satellite-based estimation of the diffuse attenuation coefficient for the downwelling spectral irradiance at the wavelength 490 nm, Kd(490), or the diffuse attenuation coefficient for the downwelling photosynthetically available radiation (PAR), Kd(PAR). An empirical algorithm has been used to routinely produce NASA standard Kd(490) product from the Moderate Resolution Imaging Spectroradiometer (MODIS).
Evaluation of Compton scattering and self-attenuation coefficient after ? -ray analysis of naturally occurring radioactive elements in environmental samples
A. A. El-Sayed
Comparison of Compton scattering and Compton scattering cross section with self-attenuation coefficient were explained based\\u000a on the kinematic equation and Klein-Nishina formula. Naturally occurring elements, 238U (226Ra), 40K, 232Th (228Ra) and 137Cs were determined in sediments and water from Ismailia canal in Egypt which were found in the range of permissible level.\\u000a Self-attenuation coefficients, K, the ratio between photopeak detection
Dynamic changes of integrated backscatter, attenuation coefficient and bubble activities during high-intensity focused ultrasound (HIFU) treatment.
Zhang, Siyuan; Wan, Mingxi; Zhong, Hui; Xu, Cheng; Liao, Zhenzhong; Liu, Huanqing; Wang, Supin
This paper simultaneously investigated the transient characteristics of integrated backscatter (IBS), attenuation coefficient and bubble activities as time traces before, during and after HIFU treatment, with different HIFU parameters (acoustic power and duty cycle) in both transparent tissue-mimicking phantoms and freshly excised bovine livers. These dynamic changes of acoustic parameters and bubble activities were correlated with the visualization of lesion development selected from photos, conventional B-mode ultrasound images and differential IBS images over the whole procedure of HIFU treatment. Two-dimensional radiofrequency (RF) data were acquired by a modified diagnostic ultrasound scanner to estimate the changes of mean IBS and attenuation coefficient averaged in the lesion region, and to construct the differential IBS images and B-mode ultrasound images simultaneously. Bubble activities over the whole procedure of HIFU treatment were investigated by the passive cavitation detection (PCD) method and the changes in subharmonic and broadband noise were correlated with the transient characteristics of IBS and attenuation coefficient. When HIFU was switched on, IBS and attenuation coefficient increased with the appearance of bubble clouds in the B-mode and differential IBS image. At the same time, the level of subharmonic and broadband noise rose abruptly. Then, there was an initial decrease in the attenuation coefficient, followed by an increase when at lower HIFU power. As the lesion appeared, IBS and attenuation coefficient both increased rapidly to a value twice that of normal. Then the changes in IBS and attenuation coefficient showed more complex patterns, but still showed a slower trend of increases with lesion development. Violent bubble activities were visible in the gel and were evident as strongly echogenic regions in the differential IBS images and B-mode images simultaneously. This was detected by a dramatic high level of subharmonic and broadband noise at the same time. These bubble activities caused fluctuations in IBS and attenuation coefficient during HIFU treatment. After HIFU, IBS and attenuation coefficient decreased gradually accompanied by the fadeout of bright hyperechoic spot in the B-mode and differential IBS image, but were still higher than normal when they were stable. The increases of IBS and attenuation coefficient were greater when using higher acoustic power or a higher duty cycle of the therapeutic emission. These experiments indicated that the bubble activities had the dominant effects on the transient characteristics of IBS and attenuation. This should be taken into consideration when using the dynamic acoustic-property changes for the potentially real-time monitoring imaging of HIFU treatment. PMID:19716225
Estimating dynamic changes of tissue attenuation coefficient during high-intensity focused ultrasound treatment
Background This study investigated the dynamic changes of tissue attenuation coefficients before, during, and after high-intensity focused ultrasound (HIFU) treatment at different total acoustic powers (TAP) in ex vivo porcine muscle tissue. It further assessed the reliability of employing changes in tissue attenuation coefficient parameters as potential indicators of tissue thermal damage. Methods Two-dimensional pulse-echo radio frequency (RF) data were acquired before, during, and after HIFU exposure to estimate changes in least squares attenuation coefficient slope (??) and attenuation coefficient intercept (??0). Using the acquired RF data, ?? and ??0 images, along with conventional B-mode ultrasound images, were constructed. The dynamic changes of ?? and ??0, averaged in the region of interest, were correlated with B-mode images obtained during the HIFU treatment process. Results At a HIFU exposure duration of 40 s and various HIFU intensities (737¢1,068 W/cm2), ?? and ??0 increased rapidly to values in the ranges 1.5¢2.5 dB/(MHz.cm) and 4¢5 dB/cm, respectively. This rapid increase was accompanied with the appearance of bubble clouds in the B-mode images. Bubble activities appeared as strong hyperechoic regions in the B-mode images and caused fluctuations in the estimated ?? and ??0 values. After the treatment, ?? and ??0 values gradually decreased, accompanied by fade-out of hyperechoic spots in the B-mode images. At 10 min after the treatment, they reached values in ranges 0.75¢1 dB/(MHz.cm) and 1¢1.5 dB/cm, respectively, and remained stable within those ranges. At a long HIFU exposure duration of around 10 min and low HIFU intensity (117 W/cm2), ?? and ??0 gradually increased to values of 2.2 dB/(MHz.cm) and 2.2 dB/cm, respectively. This increase was not accompanied with the appearance of bubble clouds in the B-mode images. After HIFU treatment, ?? and ??0 gradually decreased to values of 1.8 dB/(MHz.cm) and 1.5 dB/cm, respectively, and remained stable at those values. Conclusions ?? and ??0 estimations were both potentially reliable indicators of tissue thermal damage. In addition, ?? and ??0 images both had significantly higher contrast-to-speckle ratios compared to the conventional B-mode images and outperformed the B-mode images in detecting HIFU thermal lesions at all investigated TAPs and exposure durations. PMID:25516802
The test is done in a radiology department or in the health care provider's office by an x-ray technician. You will lie down on the table. The pictures are then taken. You will change your body to other positions to provide ...
Dual-modality imaging of a compressible breast phantom with realistic optical and x-ray properties
NASA Astrophysics Data System (ADS)
Price, B. D.; Gibson, A. P.; Royle, G. J.
Medical imaging equipment is routinely characterised and tested using tissue equivalent phantoms. Combined x-ray and optical mammography could provide increased screening specificity over either system alone. The ongoing evaluation of this approach depends upon the development of phantoms with simultaneously breast tissue equivalent optical and x-ray properties. Furthermore deformation models used in the registration of optical and x-ray images, which are acquired at differing levels of breast compression, require validation through phantoms which are also mechanically tissue equivalent. As well as static imaging, dynamic optical imaging of blood flow whilst breast compression is applied has been proposed as a method of enhancing screening specificity. The effect of changes in blood flow and volume on optical tomography still need to be established. A novel phantom material created by freezing and thawing a solution of polyvinyl alcohol (PVAL) in ethanol to create a solid yet elastically compressible gel is described. These gels have x-ray attenuation coefficients equivalent to those of breast tissues whilst their optical and mechanical properties are readily modified. Titanium dioxide is added to the optically non-scattering and colourless gels to obtain the transport scattering coefficient required. Cancerous tissues are often many times stiffer than healthy. Similar differences in stiffness are achieved between gels by varying PVAL concentration. The first x-ray and optical images of an anthropomorphically shaped breast phantom made from this gel are presented. This contains a lesion filled with blood equivalent dye whose volume changes upon compression of the phantom.
Influence Of Scattering On The Diffuse Attenuation Coefficient In The Asymptotic Region
NASA Astrophysics Data System (ADS)
Tanis, Fred J.; Kattawar, George W.; Hickman, G. Daniel
In a homogeneous ocean that both scatters and absorbs the radiance decreases with depth and the angular dependence of the radiance becomes independent of depth and of the incident distribution at the surface. In the diffusion region the asymptotic radiance distribution is only dependent on the inherent properties of the medium including the scattering phase function. Under these conditions an exact integral equation can be derived for the asymptotic radiance. A numerical calculation of the asymptotic radiance was made with Lobatto quadrature resulting in a precise estimate of the diffuse attenuation coefficient for selected values of the single scattering albedo. Calculations were made using estimated single scattering phase functions derived from scattering measurements made for a wide variety of marine and freshwater water types. A two parameter empirical expression was derived from these model calculations relating the diffuse attenuation coefficient and the single scattering albedo. Predictions are made over the entire range of single scattering albedos and are compared to those given by other investigators. The predictability of this relationship and the influence of the scattering phase function are evaluated for each of the scattering phase functions examined. Individual derived relationships are able to predict the diffusion exponent with RMS errors of less than one percent. The overall variation in determining the two parameters is approximately 3 and 18 percent using samples which varied optically from very clear waters of Sargasso Sea to the turbid waters of Lake Erie.
NASA Technical Reports Server (NTRS)
Smith, Henry I. (Inventor); Lim, Michael (Inventor); Carter, James (Inventor); Schattenburg, Mark (Inventor)
X-ray masking apparatus includes a frame having a supporting rim surrounding an x-ray transparent region, a thin membrane of hard inorganic x-ray transparent material attached at its periphery to the supporting rim covering the x-ray transparent region and a layer of x-ray opaque material on the thin membrane inside the x-ray transparent region arranged in a pattern to selectively transmit x-ray energy entering the x-ray transparent region through the membrane to a predetermined image plane separated from the layer by the thin membrane. A method of making the masking apparatus includes depositing back and front layers of hard inorganic x-ray transparent material on front and back surfaces of a substrate, depositing back and front layers of reinforcing material on the back and front layers, respectively, of the hard inorganic x-ray transparent material, removing the material including at least a portion of the substrate and the back layers of an inside region adjacent to the front layer of hard inorganic x-ray transparent material, removing a portion of the front layer of reinforcing material opposite the inside region to expose the surface of the front layer of hard inorganic x-ray transparent material separated from the inside region by the latter front layer, and depositing a layer of x-ray opaque material on the surface of the latter front layer adjacent to the inside region.
Monitoring X-Ray Emission from X-Ray Bursters
NASA Technical Reports Server (NTRS)
Kaaret, Philip
The goal of this investigation was to use the All-Sky Monitor on the Rossi X-Ray Timing Explorer (RXTE) in combination with the Burst and Transient Source Experiment on the Compton Gamma-Ray Observatory to simultaneously measure the x-ray (2-12 keV) and hard x-ray (20-100 keV) emission from x-ray bursters. The investigation was successful. We made the first simultaneous measurement of hard and soft x-ray emission and found a strong anticorrelation of hard and soft x-ray emission from the X-Ray Burster 4U 0614+091. The monitoring performed under this investigation was also important in triggering target of opportunity observations of x-ray bursters made under the investigation hard x-ray emission of x-ray bursters approved for RXTE cycles 1 and 2. These observations lead to a number of papers on high-frequency quasi-periodic oscillations and on hard x-ray emission from the x-ray bursters 4U 0614+091 and 4U 1705-44.
Dimensionality and noise in energy selective x-ray imaging
Alvarez, Robert E.
Purpose: To develop and test a method to quantify the effect of dimensionality on the noise in energy selective x-ray imaging. Methods: The CramĶr-Rao lower bound (CRLB), a universal lower limit of the covariance of any unbiased estimator, is used to quantify the noise. It is shown that increasing dimensionality always increases, or at best leaves the same, the variance. An analytic formula for the increase in variance in an energy selective x-ray system is derived. The formula is used to gain insight into the dependence of the increase in variance on the properties of the additional basis functions, the measurement noise covariance, and the source spectrum. The formula is also used with computer simulations to quantify the dependence of the additional variance on these factors. Simulated images of an object with three materials are used to demonstrate the trade-off of increased information with dimensionality and noise. The images are computed from energy selective data with a maximum likelihood estimator. Results: The increase in variance depends most importantly on the dimension and on the properties of the additional basis functions. With the attenuation coefficients of cortical bone, soft tissue, and adipose tissue as the basis functions, the increase in variance of the bone component from two to three dimensions is 1.4 ū 103. With the soft tissue component, it is 2.7 ū 104. If the attenuation coefficient of a high atomic number contrast agent is used as the third basis function, there is only a slight increase in the variance from two to three basis functions, 1.03 and 7.4 for the bone and soft tissue components, respectively. The changes in spectrum shape with beam hardening also have a substantial effect. They increase the variance by a factor of approximately 200 for the bone component and 220 for the soft tissue component as the soft tissue object thickness increases from 1 to 30 cm. Decreasing the energy resolution of the detectors increases the variance of the bone component markedly with three dimension processing, approximately a factor of 25 as the resolution decreases from 100 to 3 bins. The increase with two dimension processing for adipose tissue is a factor of two and with the contrast agent as the third material for two or three dimensions is also a factor of two for both components. The simulated images show that a maximum likelihood estimator can be used to process energy selective x-ray data to produce images with noise close to the CRLB. Conclusions: The method presented can be used to compute the effects of the object attenuation coefficients and the x-ray system properties on the relationship of dimensionality and noise in energy selective x-ray imaging systems. PMID:24320442
A Nuclear Resonant X-Ray Waveguide
D. R. Lee; Z. Islam; W. Sturhahn; C. Liu; E. E. Alp; S. K. Sinha; R. R÷hlsberger
We have prepared a nuclear resonant x-ray waveguide, consisting ^57Fe\\/C\\/^57Fe layers magnetized along the beam direction. In this waveguide, the standing-wave electric field can be resonantly excited at the guided mode inside the carbon layer (350 Angstroms) between thin ^57Fe layers (50 Angstroms) and can travel through the weakly-absorbing carbon layer without severe attenuation. With the incident angle set to
Saldin, PI: D. K.; Co-I's: J. C. H. Spence and P. Fromme
The work supported by the grant was aimed at developing novel methods of finding the structures of biomolecules using x-rays from novel sources such as the x-ray free electron laser and modern synchrotrons
Muraki, T.; Yamamura, T.
A stereoscopic x-ray device used for stereoscopic radiography generates x-rays from a pair of x-ray focal spots. The x-ray device is provided with an evacuated envelope, an x-ray target within the evacuated envelope, and a cathode structure having at least two pairs of filaments. The first pair of filaments form relatively large size x-ray focal spots on the target. The second pair of the filaments form relatively small size x-ray focal spots on the target and are situated between the first pair of filaments on the cathode structure. As a result of these two pairs of focal spots on the x-ray target, a relatively small xray device can be used to provide magnification of stereoscopic images of high stereo quality.
NSDL National Science Digital Library
In this activity, learners explore dinosaur fossils and skeletons. First, learners listen to "Tyrannosaurus Rex" by Daniel Cohen to learn about T. rex dinosaurs specifically. Then, learners make dinosaur tracings and drawings similar to x-rays. Learners can repeat the activity using pictures of other dinosaurs to compare and contrast various dinosaurs. This activity is featured on page 38 of the "Dinosphere" unit of study for K-2 learners.
Refractive Optics for Hard X-ray Transmission Microscopy
NASA Astrophysics Data System (ADS)
Simon, M.; Ahrens, G.; Last, A.; Mohr, J.; Nazmov, V.; Reznikova, E.; Voigt, A.
For hard x-ray transmission microscopy at photon energies higher than 15 keV we design refractive condenser and imaging elements to be used with synchrotron light sources as well as with x-ray tube sources. The condenser lenses are optimized for low x-ray attenuationŚresulting in apertures greater than 1 mmŚand homogeneous intensity distribution on the detector plane, whereas the imaging enables high-resolution (<100 nm) full-field imaging. To obtain high image quality at reasonable exposure times, custom-tailored matched pairs of condenser and imaging lenses are being developed. The imaging lenses (compound refractive lenses, CRLs) are made of SU-8 negative resist by deep x-ray lithography. SU-8 shows high radiation stability. The fabrication technique enables high-quality lens structures regarding surface roughness and arrangement precision with arbitrary 2D geometry. To provide point foci, crossed pairs of lenses are used. Condenser lenses have been made utilizing deep x-ray lithographic patterning of thick SU-8 layers, too, whereas in this case, the aperture is limited due to process restrictions. Thus, in terms of large apertures, condenser lenses made of structured and rolled polyimide film are more attractive. Both condenser types, x-ray mosaic lenses and rolled x-ray prism lenses (RXPLs), are considered to be implemented into a microscope setup. The x-ray optical elements mentioned above are characterized with synchrotron radiation and x-ray laboratory sources, respectively.
Refractive Optics for Hard X-ray Transmission Microscopy
Simon, M.; Last, A.; Mohr, J.; Nazmov, V.; Reznikova, E. [Institute for Microstructure Technology, Karlsruhe Institute of Technology Kaiserstrasse 12, 76131 Karlsruhe (Germany); Ahrens, G.; Voigt, A. [Microresist Technology, Koepenikerstrasse 325, 12555 Berlin (Germany)
For hard x-ray transmission microscopy at photon energies higher than 15 keV we design refractive condenser and imaging elements to be used with synchrotron light sources as well as with x-ray tube sources. The condenser lenses are optimized for low x-ray attenuation--resulting in apertures greater than 1 mm--and homogeneous intensity distribution on the detector plane, whereas the imaging enables high-resolution (<100 nm) full-field imaging. To obtain high image quality at reasonable exposure times, custom-tailored matched pairs of condenser and imaging lenses are being developed. The imaging lenses (compound refractive lenses, CRLs) are made of SU-8 negative resist by deep x-ray lithography. SU-8 shows high radiation stability. The fabrication technique enables high-quality lens structures regarding surface roughness and arrangement precision with arbitrary 2D geometry. To provide point foci, crossed pairs of lenses are used. Condenser lenses have been made utilizing deep x-ray lithographic patterning of thick SU-8 layers, too, whereas in this case, the aperture is limited due to process restrictions. Thus, in terms of large apertures, condenser lenses made of structured and rolled polyimide film are more attractive. Both condenser types, x-ray mosaic lenses and rolled x-ray prism lenses (RXPLs), are considered to be implemented into a microscope setup. The x-ray optical elements mentioned above are characterized with synchrotron radiation and x-ray laboratory sources, respectively.
NASA Technical Reports Server (NTRS)
Wu, S. T.
Dr. S. N. Zhang has lead a seven member group (Dr. Yuxin Feng, Mr. XuejunSun, Mr. Yongzhong Chen, Mr. Jun Lin, Mr. Yangsen Yao, and Ms. Xiaoling Zhang). This group has carried out the following activities: continued data analysis from space astrophysical missions CGRO, RXTE, ASCA and Chandra. Significant scientific results have been produced as results of their work. They discovered the three-layered accretion disk structure around black holes in X-ray binaries; their paper on this discovery is to appear in the prestigious Science magazine. They have also developed a new method for energy spectral analysis of black hole X-ray binaries; four papers on this topics were presented at the most recent Atlanta AAS meeting. They have also carried Monte-Carlo simulations of X-ray detectors, in support to the hardware development efforts at Marshall Space Flight Center (MSFC). These computation-intensive simulations have been carried out entirely on the computers at UAH. They have also carried out extensive simulations for astrophysical applications, taking advantage of the Monte-Carlo simulation codes developed previously at MSFC and further improved at UAH for detector simulations. One refereed paper and one contribution to conference proceedings have been resulted from this effort.
Anisotropy of intrinsic attenuation in the Earth's inner core: quantitative models from normal mode splitting function coefficients
NASA Astrophysics Data System (ADS)
Makinen, A.; Deuss, A. F.; Redfern, S. A.
Seismic normal mode and body wave studies find that the Earth's inner core is characterized by strong, large-scale average, cylindrically symmetric velocity anisotropy: compressional waves traversing the inner core in the North-South (polar) direction propagate faster than those travelling in the equatorial plane. Compressional body wave studies also suggest that the inner core exhibit anisotropy of attenuation, finding that compressional waves are also more strongly attenuated in the fast direction. This relationship between anisotropy of velocity and attenuation in the metallic inner core is the reverse of that observed in the silicate mantle; thus far, the existing body wave observations of anisotropic attenuation have been interpreted almost exclusively in terms of anisotropic scattering attenuation. However, body waves cannot distinguish between attenuation by intrinsic (anelastic) mechanisms and by scattering, which prevents us from understanding the physical origin of the attenuation anisotropy. Here, we elucidate attenuation anisotropy using normal modes, the low-frequency free oscillations of the planet as a whole. Due to their very long wavelengths, normal modes are transparent to scattering from small-scale heterogeneities; this makes them a particularly valuable tool for probing the intrinsic component of attenuation, and its possible anisotropy. They are also simultaneously sensitive to both compressional and shear wave properties of the inner core, unlike the various inner core body wave phases. Here, we invert our recently measured anelastic normal mode splitting function coefficients of inner core sensitive normal modes and present a new model of attenuation anisotropy of the Earth's inner core. Our model reveals that the intrinsic attenuation is anisotropic, and confirms that for compressional waves, attenuation anisotropy is indeed correlated with velocity anisotropy, with the fast direction being also more attenuating. Such anisotropy of intrinsic attenuation has the characteristics of anisotropic Zener-like relaxations within single iron crystals due to the reorientation of pairs of solute atoms, and confirms the necessity of incorporating a few per cent of light elements into the solid inner core.
... technician takes the X-rays. An X-ray technician in the radiology department of a hospital or a health care ... how the lateral view usually is done. The technician will return to reposition your ... be brought to the radiology department, a portable X-ray machine can be ...
... X-rays are performed by an X-ray technician in the radiology department of a hospital, a radiology center, or ... and can't easily be brought to the radiology department, a portable X-ray ... rooms. The technician will seat your child, position the forearm on ...
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... x-rays. top of page What does the equipment look like? View larger with caption The equipment typically used for bone x-rays consists of ... and joint abnormalities, such as arthritis. X-ray equipment is relatively inexpensive and widely available in emergency ...
Boyce, James R. (Williamsburg, VA)
A method for the production of X-ray bunches tunable in both time and energy level by generating multiple photon, X-ray, beams through the use of Thomson scattering. The method of the present invention simultaneously produces two X-ray pulses that are tunable in energy and/or time.
Profiling of Fiber Texture Gradients by Anomalous X-ray Diffraction
NASA Astrophysics Data System (ADS)
Birkholz, M.; Darowski, N.; Zizak, I.
Preferred crystallographic orientation or texture is a typically observed phenomenon in polycrystalline thin films. In addition, texture was revealed in numerous x-ray diffraction studies to increase with layer thickness. The phenomenon is rather significant for the optimized preparation of thin films, but was difficult to measure so far. A method is presented that allows for texture profiling by exploiting the anomalous variation of the x-ray attenuation coefficient in the vicinity of an elemental absorption edge. The study reports the application of the technique to thin ZnO:Al films by measuring with wavelengths below and above the Zn K edge. Large texture gradients between 0.03 and 0.3 mrd/nm were revealed to arise in these samples. Anomalous diffraction is concluded to enable the determination of texture gradients as required in many thin film projects.
Bulk-Sensitive X-Ray Absorption Spectroscopy Free of Self-Absorption
NASA Astrophysics Data System (ADS)
Achkar, Andrew; Regier, Tom; Wadati, Hiroki; Sawatzky, George; Kim, Young-June; Hawthorn, David
We demonstrate a new method to measure x-ray absorption spectroscopy (XAS) in addition to traditional transmission, total-electron yield (TEY) and total-fluorescence yield (TFY) that is bulk sensitive, like TFY, and is not affected by self-absorption corrections that plague TFY measurements. This measure of XAS is accomplished by measuring the x-ray emission (partial fluorescence yield, PFY) from a different element or excitation than the one probed by the incident photon energy. It is found that the reciprocal of such a PFY spectrum is proportional to the linear attenuation coefficient, offset by an energy independent constant. We demonstrate this technique on Cu L, La M and Nd M edges of the high-TC cuprate La2-x-yNdySrxCuO4 by comparing its TEY, TFY and PFY spectra.
Matthews, D.L.; Rosen, M.D.
One of the elusive dreams of laser physicists has been the development of an x-ray laser. After 25 years of waiting, the x-ray laser has at last entered the scientific scene, although those now in operation are still laboratory prototypes. They produce soft x rays down to about five nanometers. X-ray lasers retain the usual characteristics of their optical counterparts: a very tight beam, spatial and temporal coherence, and extreme brightness. Present x-ray lasers are nearly 100 times brighter that the next most powerful x-ray source in the world: the electron synchrotron. Although Lawrence Livermore National Laboratory (LLNL) is widely known for its hard-x-ray laser program which has potential applications in the Strategic Defense Initiative, the soft x-ray lasers have no direct military applications. These lasers, and the scientific tools that result from their development, may one day have a place in the design and diagnosis of both laser fusion and hard x-ray lasers. The soft x-ray lasers now in operation at the LLNL have shown great promise but are still in the primitive state. Once x-ray lasers become reliable, efficient, and economical, they will have several important applications. Chief among them might be the creation of holograms of microscopic biological structures too small to be investigated with visible light. 5 figs.
Piestrup, Melvin A. (Woodside, CA); Boyers, David G. (Mountain View, CA); Pincus, Cary (Sunnyvale, CA)
A high-intensity, inexpensive X-ray source for X-ray lithography for the production of integrated circuits. Foil stacks are bombarded with a high-energy electron beam of 25 to 250 MeV to produce a flux of soft X-rays of 500 eV to 3 keV. Methods of increasing the total X-ray power and making the cross section of the X-ray beam uniform are described. Methods of obtaining the desired X-ray-beam field size, optimum frequency spectrum and elminating the neutron flux are all described. A method of obtaining a plurality of station operation is also described which makes the process more efficient and economical. The satisfying of these issues makes transition radiation an exellent moderate-priced X-ray source for lithography.
Piestrup, M.A.; Boyers, D.G.; Pincus, C.
A high-intensity, inexpensive X-ray source for X-ray lithography for the production of integrated circuits is disclosed. Foil stacks are bombarded with a high-energy electron beam of 25 to 250 MeV to produce a flux of soft X-rays of 500 eV to 3 keV. Methods of increasing the total X-ray power and making the cross section of the X-ray beam uniform are described. Methods of obtaining the desired X-ray-beam field size, optimum frequency spectrum and eliminating the neutron flux are all described. A method of obtaining a plurality of station operation is also described which makes the process more efficient and economical. The satisfying of these issues makes transition radiation an excellent moderate-priced X-ray source for lithography. 26 figures.
Dependence of optical attenuation coefficient and mechanical tension of irradiated human cartilage measured by optical coherence tomography.
Martinho Junior, A C; Freitas, A Z; Raele, M P; Santin, S P; Soares, F A N; Herson, M R; Mathor, M B
As banked human tissues are not widely available, the development of new non-destructive and contactless techniques to evaluate the quality of allografts before distribution for transplantation is very important. Also, tissues will be processed accordingly to standard procedures and to minimize disease transmission most tissue banks will include a decontamination or sterilization step such as ionizing radiation. In this work, we present a new method to evaluate the internal structure of frozen or glycerol-processed human cartilages, submitted to various dosis of irradiation, using the total optical attenuation coefficient retrieved from optical coherence tomography (OCT) images. Our results show a close relationship between tensile properties and the total optical attenuation coefficient of cartilages. Therefore, OCT associated with the total optical attenuation coefficient open a new window to evaluate quantitatively biological changes in processed tissues. PMID:24322969
Noninvasive monitoring of photodynamic therapy on skin neoplastic lesions using the optical attenuation coefficient measured by optical coherence tomography.
Goulart, Viviane P; dos Santos, Moisķs O; Latrive, Anne; Freitas, Anderson Z; Correa, Luciana; Zezell, Denise M
Photodynamic therapy (PDT) has become a promising alternative for treatment of skin lesions such as squamous cell carcinoma. We propose a method to monitor the effects of PDT in a noninvasive way by using the optical attenuation coefficient (OAC) calculated from optical coherence tomography (OCT) images. We conducted a study on mice with chemically induced neoplastic lesions and performed PDT on these lesions using homemade photosensitizers. The response of neoplastic lesions to therapy was monitored using, at the same time, macroscopic clinical visualization, histopathological analysis, OCT imaging, and OCT-based attenuation coefficient measurement. Results with all four modalities demonstrated a positive response to treatment. The attenuation coefficient was found to be 1.4 higher in skin lesions than in healthy tissue and it decreased after therapy. This study shows that the OAC is a potential tool to noninvasively assess the evolution of skin neoplastic lesions with time after treatment. PMID:25415566
NASA Technical Reports Server (NTRS)
Saba, J. L. R.
The objective of the X-ray Polychromator (XRP) experiment was to study the physical properties of solar flare plasma and its relation to the parent active region to understand better the flare mechanism and related solar activity. Observations were made to determine the temperature, density, and dynamic structure of the pre-flare and flare plasma as a function of wavelength, space and time, the extent to which the flare plasma departs from thermal equilibrium, and the variation of this departure with time. The experiment also determines the temperature and density structure of active regions and flare-induced changes in the regions.
PXAMS -- Projectile X ray AMS: X ray yields and applications
McAninch, J.E.; Bench, G.S.; Freeman, S.P.H.T.; Roberts, M.L.; Southon, J.R.; Vogel, J.S.; Proctor, I.D. [Lawrence Livermore National Lab., CA (United States). Center for Accelerator Mass Spectrometry
Characteristic x rays have recently been explored as a method for the detection and identification of ions in accelerator mass spectrometry (AMS). After analysis in the AMS spectrometer, the ions stop in an appropriately chosen target and the induced x rays identify the ions by atomic number. For the application of AMS to higher mass isotopes, characteristic x rays allow significantly better discrimination of competing atomic isobars than is possible using energy loss detectors. Characteristic x rays also show promise as a convenient component in hybrid detection systems. Measurements of x ray yields are presented for Si, Fe, Ni, Se, Mo, and Pd ions of 0.5--2 MeV/AMU. The yields rise by more than a factor of 10 over this energy range, and approach 1 x-ray per incident ion at 2 MeV/AMU for the lighter ions. Preliminary work on the application of PXAMS to the detection of {sup 79}Se is described.
Willi A. Kalender; Paul Deak; Klaus Engelke; Marek Karolczak
\\u000a Since their discovery in 1895, X-rays have been widely used for imaging humans. Recently, they have also gained an importance\\u000a in small animal imaging (SAI). Most techniques known from clinical medicine, including single- and dual-energy X-ray imaging,\\u000a have been successfully ported to SAI and are the subject of this chapter. As trivial as it is, simple X-ray examinations may\\u000a bring
Comparison of Chang's with Sorenson's Attenuation Correction Method by Varying Linear Attenuation Coefficient Values in Tc99m SPECT Imaging
Inayatullah Shah Sayed; Ahmed Zakaria; Norhafiza Nik
Attenuation (scattering and absorption) of gamma photons in the patientÆs body is one of the major limitations among the others\\u000a in single photon emission computed tomography (SPECT). It reduces quantitative accuracy of measured radioactivity concentration\\u000a and causes hot rim artifacts in reconstructed images if not corrected for. A variety of approximate attenuation correction\\u000a methods has been developed or proposed by
Linear attenuation coefficient and buildup factor of MCP-96 alloy for dose accuracy, beam collimation, and radiation protection.
Hopkins, Deidre N; Maqbool, Muhammad; Islam, Mohammed S
The linear attenuation coefficients and buildup factor of MCP-96 alloy were determined for (60)Co, (54)Mn, and (137)Cs gamma emitters and a NaI detector. The thickness of the MCP-96 attenuator was varied from 1 to 4 cm. A collimated beam of gamma rays was allowed to pass through various thicknesses of the MCP-96 alloy. The attenuated beam was detected by a NaI detector, and data were recorded by a multichannel analyzer. The run was repeated without the collimator for broad-beam geometry. For each run, the attenuated beam intensity was normalized by the intensity of the unattenuated incident beam obtained by removing the attenuators. Linear attenuation coefficients were determined by plotting of the intensity of the collimated beam against the attenuator thickness. For every thickness of the alloy, the ratio of the attenuated to the unattenuated beam was found to be higher in broad-beam geometry as compared to the same ratio in narrow-beam geometry. We used the difference in these ratios in broad and narrow-beam geometries to calculate the buildup factor. The buildup factor was found to increase with beam energy and attenuator thickness. Variation in the source-to-detector distance gave a lower value of the buildup factor for a small and a large distance and a higher value for an intermediate distance. The buildup factor was found to be greater than 1 in all cases. We conclude that the buildup factor must be calculated and incorporated for dose correction and precision when the MCP-96 alloy is used for tissue compensation or radiation shielding and protection purposes. PMID:22585280
ERIC Educational Resources Information Center
Lynch, Mark
We continue our study of topological X-rays begun in Lynch ["Topological X-rays and MRI's," iJMEST 33(3) (2002), pp. 389-392]. We modify our definition of a topological magnetic resonance imaging and give an affirmative answer to the question posed there: Can we identify a closed set in a box by defining X-rays to probe the interior and withoutģ
Diffuse Attenuation Coefficient of Downwelling Irradiance: An Evaluation of Remote Sensing Methods
NASA Technical Reports Server (NTRS)
Lee, Zhong-Ping; Darecki, Miroslaw; Carder, Kendall L.; Davis, Curtiss O.; Stramski, Dariusz; Rhea, W. Joseph
The propagation of downwelling irradiance at wavelength lambda from surface to a depth (z) in the ocean is governed by the diffuse attenuation coefficient, K(sup -)(sub d)(lambda). There are two standard methods for the derivation of K(sup -)(sub d)(lambda) in remote sensing, which both are based on empirical relationships involving the blue-to-green ratio of ocean color. Recently, a semianalytical method to derive K(sup -)(sub d)(lambda) from reflectance has also been developed. In this study, using K(sup -)(sub d)(490) and K(sup -)(sub d)(443) as examples, we compare the K(sup -)(sub d)(lambda) values derived from the three methods using data collected in three different regions that cover oceanic and coastal waters, with K(sup -)(sub d)(490) ranging from approximately 0.04 to 4.0 per meter. The derived values are compared with the data calculated from in situ measurements of the vertical profiles of downwelling irradiance. The comparisons show that the two standard methods produced satisfactory estimates of K(sup -)(sub d)(lambda) in oceanic waters where attenuation is relatively low but resulted in significant errors in coastal waters. The newly developed semianalytical method appears to have no such limitation as it performed well for both oceanic and coastal waters. For all data in this study the average of absolute percentage difference between the in situ measured and the semianalytically derived K(sup -)(sub d) is approximately 14% for lambda = 490 nm and approximately 11% for lambda = 443 nm.
Yano, Junko; Yachandra, Vittal K.
This review gives a brief description of the theory and application of X-ray absorption spectroscopy, both X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), especially, pertaining to photosynthesis. The advantages and limitations of the methods are discussed. Recent advances in extended EXAFS and polarized EXAFS using oriented membranes and single crystals are explained. Developments in theory in understanding the XANES spectra are described. The application of X-ray absorption spectroscopy to the study of the Mn4Ca cluster in Photosystem II is presented.
Prediction of the light attenuation coefficient through the Secchi disk depth: empirical modeling in two large Neotropical ecosystems
Andrķ Andrian Padial; Sidinei Magela Thomaz
The easiest way to evaluate water transparency is from the Secchi disk depth (SD). The behavior of radiation passing through\\u000a water can also be quantified by the light attenuation coefficient (k) of photosynthetically active radiation (PAR), measured using quanta meters. Due to the high costs of quanta meters, k is usually predicted from SD. This prediction can be made using
Precise measurement of attenuation coefficients of gamma rays in the 7.5 MeV region
R. Moreh; D. Salzmann; Y. Wand
A new technique utilising nuclear resonance scattering of gamma rays was used for measuring total attenuation coefficients of 15 elements between Be and U. The gamma-ray energies were 7.279 and 7.646 MeV, and the results were found to be generally higher than the calculated values.
Evaluation of moisture-related attenuation coefficient and water diffusion velocity in human skin using optical coherence tomography.
Lee, Cheng-Kuang; Tsai, Meng-Tsan; Chang, Feng-Yu; Yang, Chih-Hsun; Shen, Su-Chin; Yuan, Ouyang; Yang, Chih-He
In this study, time-resolved optical coherence tomography (OCT) scanning images of the process of water diffusion in the skin that illustrate the enhancement in the backscattered intensities due to the increased water concentration are presented. In our experiments, the water concentration in the skin was increased by soaking the hand in water, and the same region of the skin was scanned and measured with the OCT system and a commercial moisture monitor every three minutes. To quantitatively analyze the moisture-related optical properties and the velocity of water diffusion in human skin, the attenuation coefficients of the skin, including the epidermis and dermis layers, were evaluated. Furthermore, the evaluated attenuation coefficients were compared with the measurements made using the commercial moisture monitor. The results demonstrate that the attenuation coefficient increases as the water concentration increases. Furthermore, by evaluating the positions of center-of mass of the backscattered intensities from OCT images, the diffusion velocity can be estimated. In contrast to the commercial moisture monitor, OCT can provide three-dimensional structural images of the skin and characterize its optical property, which together can be used to observe morphological changes and quantitatively evaluate the moisture-related attenuation coefficients in different skin layers. PMID:23529149
Ancient administrative handwritten documents: X-ray analysis and imaging.
Albertin, F; Astolfo, A; Stampanoni, M; Peccenini, Eva; Hwu, Y; Kaplan, F; Margaritondo, G
Handwritten characters in administrative antique documents from three centuries have been detected using different synchrotron X-ray imaging techniques. Heavy elements in ancient inks, present even for everyday administrative manuscripts as shown by X-ray fluorescence spectra, produce attenuation contrast. In most cases the image quality is good enough for tomography reconstruction in view of future applications to virtual page-by-page `reading'. When attenuation is too low, differential phase contrast imaging can reveal the characters from refractive index effects. The results are potentially important for new information harvesting strategies, for example from the huge Archivio di Stato collection, objective of the Venice Time Machine project. PMID:25723946
Radiation dose estimation and mass attenuation coefficients of cement samples used in Turkey.
Damla, N; Cevik, U; Kobya, A I; Celik, A; Celik, N; Van Grieken, R
Different cement samples commonly used in building construction in Turkey have been analyzed for natural radioactivity using gamma-ray spectrometry. The mean activity concentrations observed in the cement samples were 52, 40 and 324 Bq kg(-1) for (226)Ra, (232)Th and (40)K, respectively. The measured activity concentrations for these radionuclides were compared with the reported data of other countries and world average limits. The radiological hazard parameters such as radium equivalent activities (Ra(eq)), gamma index (I(gamma)) and alpha index (I(alpha)) indices as well as terrestrial absorbed dose and annual effective dose rate were calculated and compared with the international data. The Ra(eq) values of cement are lower than the limit of 370 Bq kg(-1), equivalent to a gamma dose of 1.5 mSv y(-1). Moreover, the mass attenuation coefficients were determined experimentally and calculated theoretically using XCOM in some cement samples. Also, chemical compositions analyses of the cement samples were investigated. PMID:20018450
von Goeler, S.; Hill, K.W.; Bitter, M.
A short description of the x-ray diagnostic preparation for the TFTR tokamak is given. The x-ray equipment consists of the limiter x-ray monitoring system, the soft x-ray pulse-height-analysis-system, the soft x-ray imaging system and the x-ray crystal spectrometer. Particular attention is given to the radiation protection of the x-ray systems from the neutron environment.
... through them and appear darker. An X-ray technician in the radiology department of a hospital or a health care ... and can't easily be brought to the radiology department, a portable X-ray machine ... rooms. The technician will position your child on the table, and ...
NASA Technical Reports Server (NTRS)
Jordan, E. H.; Pease, D. M.
A totally new method of extensometry using an X-ray beam was proposed. The intent of the method is to provide a non-contacting technique that is immune to problems associated with density variations in gaseous environments that plague optical methods. X-rays are virtually unrefractable even by solids. The new method utilizes X-ray induced X-ray fluorescence or X-ray induced optical fluorescence of targets that have melting temperatures of over 3000 F. Many different variations of the basic approaches are possible. In the year completed, preliminary experiments were completed which strongly suggest that the method is feasible. The X-ray induced optical fluorescence method appears to be limited to temperatures below roughly 1600 F because of the overwhelming thermal optical radiation. The X-ray induced X-ray fluorescence scheme appears feasible up to very high temperatures. In this system there will be an unknown tradeoff between frequency response, cost, and accuracy. The exact tradeoff can only be estimated. It appears that for thermomechanical tests with cycle times on the order of minutes a very reasonable system may be feasible. The intended applications involve very high temperatures in both materials testing and monitoring component testing. Gas turbine engines, rocket engines, and hypersonic vehicles (NASP) all involve measurement needs that could partially be met by the proposed technology.
Multiparameter optimization of mammography with alternative x-ray sources
NASA Astrophysics Data System (ADS)
Jafroudi, Hamid; Jennings, Robert J.; Muntz, E. P.; Freedman, Matthew T.; Mun, Seong K.
The conventional x-ray source for mammography, with a molybdenum (Mo) anode and Mo filter, works well for breasts of low to moderate x-ray attenuation, but is not readily adaptable to the production of higher x-ray energies that are more suitable for imaging breasts of higher attenuation. Accordingly, alternative sources with anodes of rhodium (Rh) and tungsten (W) have been developed to improve the efficiency of the examination for thick or radiographically dense breasts. We have applied previously developed multiparameter optimization techniques to imaging systems using these alternative x-ray sources. Since these sources are intended to improve mammography of high-attenuation breasts, optimizations were performed for a range of breast thicknesses. Since high attenuation is generally associated with high scatter, optimizations for each source were done with a high-ratio, air-interspace grid similar to the one developed in our previous work. Preliminary results have been obtained for optimized system configurations using a W-anode source with Mo, Rh, and aluminum (Al) filters, and for a Mo-anode source with Rh filtration. These results indicate that the alternative sources studied can significantly improve the efficiency of mammography of high-attenuation breasts.
Koch, Jeffrey A. (Livermore, CA)
An x-ray interferometer for analyzing high density plasmas and optically opaque materials includes a point-like x-ray source for providing a broadband x-ray source. The x-rays are directed through a target material and then are reflected by a high-quality ellipsoidally-bent imaging crystal to a diffraction grating disposed at 1.times. magnification. A spherically-bent imaging crystal is employed when the x-rays that are incident on the crystal surface are normal to that surface. The diffraction grating produces multiple beams which interfere with one another to produce an interference pattern which contains information about the target. A detector is disposed at the position of the image of the target produced by the interfering beams.
NASA Technical Reports Server (NTRS)
Blake, David F. (Inventor); Bryson, Charles (Inventor); Freund, Friedmann (Inventor)
An x-ray diffraction apparatus for use in analyzing the x-ray diffraction pattern of a sample is introduced. The apparatus includes a beam source for generating a collimated x-ray beam having one or more discrete x-ray energies, a holder for holding the sample to be analyzed in the path of the beam, and a charge-coupled device having an array of pixels for detecting, in one or more selected photon energy ranges, x-ray diffraction photons produced by irradiating such a sample with said beam. The CCD is coupled to an output unit which receives input information relating to the energies of photons striking each pixel in the CCD, and constructs the diffraction pattern of photons within a selected energy range striking the CCD.
Single-experiment simultaneous-measurement of elemental mass-attenuation coefficients of hydrogen, carbon and oxygen for 0.123¢1.33 MeV gamma rays
M. T. Teli; R. Nathuram; C. S. Mahajan
As it is inconvenient to use elements like hydrogen, carbon and oxygen in pure forms for measurement of their gamma mass-attenuation coefficients, the measurements are to be done indirectly, by using compounds of the elements or a mixture of them. We give here a simple method of measuring the total mass-attenuation coefficients ?\\/? of the elements in a compound simultaneously
The precise measurement of the attenuation coefficients of various IR optical materials applicable to immersion grating
NASA Astrophysics Data System (ADS)
Kaji, Sayumi; Sarugaku, Yuki; Ikeda, Yuji; Kobayashi, Naoto; Nakanishi, Kenshi; Kondo, Sohei; Yasui, Chikako; Kawakita, Hideyo
Immersion grating is a next-generation diffraction grating which has the immersed the diffraction surface in an optical material with high refractive index of n > 2, and can provide higher spectral resolution than a classical reflective grating. Our group is developing various immersion gratings from the near- to mid-infrared region (Ikeda et al.1, 2, 3, 4, Sarugaku et al.5, and Sukegawa et al.6). The internal attenuation ?att of the candidate materials is especially very important to achieve the high efficiency immersion gratings used for astronomical applications. Nevertheless, because there are few available data as ?att < 0.01cm-1 in the infrared region, except for measurements of CVD-ZnSe, CVD-ZnS, and single-crystal Si in the short near-infrared region reported by Ikeda et al.7, we cannot select suitable materials as an immersion grating in an aimed wavelength range. Therefore, we measure the attenuation coefficients of CdTe, CdZnTe, Ge, Si, ZnSe, and ZnS that could be applicable to immersion gratings. We used an originally developed optical unit attached to a commercial FTIR which covers the wide wavelength range from 1.3?m to 28?m. This measurement system achieves the high accuracy of (triangle)?att ~ 0.01cm-1. As a result, high-resistivity single-crystal CdZnTe, single-crystal Ge, single-crystal Si, CVD-ZnSe, and CVD-ZnS show ?att < 0.01cm-1 at the wavelength range of 5.5 - 19.0?m, 2.0 - 10.5?m, 1.3 - 5.4?m, 1.7 - 13.2?m, and 1.9 - 9.2?m, respectively. This indicates that these materials are good candidates for high efficiency immersion grating covering those wavelength ranges. We plan to make similar measurement under the cryogenic condition as T <= 10K for the infrared, especially mid-infrared applications.
An X-ray diffraction study of titanium oxidation
NASA Technical Reports Server (NTRS)
Wiedemann, K. E.; Unnam, J.
Titanium specimens of commercial purity were exposed at 1100 to 1400 F to laboratory air for times up to 100 hours. The extent of substrate contamination by interstitial oxygen was was determined by a new X-ray diffraction analysis involving transformation of X-ray diffraction intensity bands. The oxygen solid-solubility at the oxide-metal interfaces and its variation with time at temperature were also determined. Diffusion coefficients are deduced from the oxygen depth profiles.
Aluminum Alloy X-ray Image Classification Using Texture Analysis
Jun Lu; Qiuqi Ruan
This paper presents an automatic classification approach to the X-ray image classification issue of aluminum alloy by image texture analysis methods. Different from the common processing methods, the texture-based approach (XTexture) treats the X-ray image as a special texture image for further processing. By extracting self-correlation moment and wavelet-coefficient moments as the basic classification features based on image texture analysis,
Auger Electrons via K? X-Ray Lines of Platinum Compounds for Nanotechnological Applications
NASA Astrophysics Data System (ADS)
Nahar, Sultana N.; Lim, Sara; Pradhan, A. K.; Pitzer, R. M.
We will report study on the K? X-ray lines of platinum. Pt compounds, such as cisplatin, are common in biomedical applications. The active element Pt can emit or absorb hard X-rays. We have obtained the photoionization cross sections from the oscillator strengths of 1s-2p (K?) transitions in Pt ions. We find that these transitions appear as resonances in photoionization in the hard X-ray energy range of 64 - 71 keV (0.18 - 0.17 ┼) below the K-shell ionization and with a strength orders of magnitude higher compared to that at the K-shell ionization. This is the focus of our study for possible initiation of an emission cascade of Auger electrons at the resonant energy. We will present the oscillator strengths and attenuation coefficients per unit mass for all the K? transitions in the event platinum cascades through various, namely from fluorine-like to hydrogen like, ionic states. The study is motivated by uur proposed method, Resonant Theranosticsb,C (RT) for biomedical appliations, which aims to find narrow band X-ray energy that corresponds to resonant photo-absorption and leads to emission of Auger electrons. As the next step of the RT method we will also report on experimental results on producing monochromatic X-rays, targeted to the resonant energy, from the wide band Bremstruhlung radiation of a conventional X-ray source. Partially support: DOE, Computational Facility: Ohio Supercomputer Center, Columbus, Ohio. "Resonant X-Ray Enhancement of the Auger Effect in High-Z atoms, molecules, and Nanoparticles: Biomedical Applications", A.K. Pradhan, S.N. Nahar, M. Montenegro, Yan Yu, H.L. Zhang, C. Sur, M. Mrozik, R.M. Pitzer, J. of Phys. Chem. A, 113 (2009), 12356. "Monte Carlo Simulations and Atomic Calculations for Auger Processes in Biomedical Nanotheranostics", M. Montenegro, S. N. Nahar, A. K. Pradhan, Ke Huang, Yan Yu, J. of Phys. Chem. A, 113 (2009), 12364.
Using water quality variables to predict light attenuation coefficient: case study in Shihmen Reservoir
Wen-Cheng Liu; Ray-Shyan Wu; Edward Ming-Yang Wu; Yu-Pei Chang; Wei-Bo Chen
The amount of photosynthetically active radiation (PAR) in the water column is of fundamental importance in determining the\\u000a growth of aquatic plant and aquatic primary production. Light attenuation in aquatic ecosystems has important ecological implication\\u000a and water quality applications. In the present study, the light attenuation through the water column in the Shihmen Reservoir,\\u000a Taiwan was measured. A light attenuation
X-ray observations of ultraluminous X-ray sources
T. P. Roberts
Ultraluminous X-ray sources (ULXs) are amongst the most intriguing of X-ray source classes. Their extreme luminosities - greater than 10^39 erg/s in the 0.3 - 10 keV band alone - suggest either the presence of black holes larger than those regularly encountered in our own Galaxy (the Galactic centre excepted), or sources apparently radiating well above the Eddington limit. We review the insights afforded us by studies of their X-ray emission, focussing on what this reveals about the underlying compact object. In particular, we discuss recent deep observations of ULXs by the XMM-Newton observatory, and how the unprecedented data quality provided by this mission is starting to discriminate between the different physical models for these extraordinary X-ray emitters.
NASA Technical Reports Server (NTRS)
The FluoroScan Imaging System is a high resolution, low radiation device for viewing stationary or moving objects. It resulted from NASA technology developed for x-ray astronomy and Goddard application to a low intensity x-ray imaging scope. FlouroScan Imaging Systems, Inc, (formerly HealthMate, Inc.), a NASA licensee, further refined the FluoroScan System. It is used for examining fractures, placement of catheters, and in veterinary medicine. Its major components include an x-ray generator, scintillator, visible light image intensifier and video display. It is small, light and maneuverable.
Automatic detection of bone fragments in poultry using multi-energy x-rays
Gleason, Shaun S. (Knoxville, TN); Paulus, Michael J. (Knoxville, TN); Mullens, James A. (Knoxville, TN)
At least two linear arrays of x-ray detectors are placed below a conveyor belt in a poultry processing plant. Multiple-energy x-ray sources illuminate the poultry and are detected by the detectors. Laser profilometry is used to measure the poultry thickness as the x-ray data is acquired. The detector readout is processed in real time to detect the presence of small highly attenuating fragments in the poultry, i.e., bone, metal, and cartilage.
Highly-Iodinated Fullerene as a Contrast Agent For X-ray Imaging
Tim Wharton; Lon J. Wilson
The first fullerene-based X-ray contrast agent (CA) has been designed, synthesized, and characterized. The new CA is an externally functionalized derivative of C60 that is conceptually based on contemporary X-ray CA, all of which use iodine as the X-ray attenuating vehicle and are based on the 2,4,6-triiodinated-benzene-ring substructure. Using a modified Bingel-type reaction, a single addend containing 6 iodine atoms
Water equivalence of NIPAM based polymer gel dosimeters with enhanced sensitivity for x-ray CT
NASA Astrophysics Data System (ADS)
Gorjiara, Tina; Hill, Robin; Bosi, Stephen; Kuncic, Zdenka; Baldock, Clive
Two new formulations of N-isopropylacrylamide (NIPAM) based three dimensional (3D) gel dosimeters have recently been developed with improved sensitivity to x-ray CT readout, one without any co-solvent and the other one with isopropanol co-solvent. The water equivalence of the NIPAM gel dosimeters was investigated using different methods to calculate their radiological properties including: density, electron density, number of electrons per grams, effective atomic number, photon interaction probabilities, mass attenuation and energy absorption coefficients, electron collisional, radiative and total mass stopping powers and electron mass scattering power. Monte Carlo modelling was also used to compare the dose response of these gel dosimeters with water for kilovoltage and megavoltage x-ray beams and for megavoltage electron beams. We found that the density and electron density of the co-solvent free gel dosimeter are more water equivalent with less than a 2.6% difference compared to a 5.7% difference for the isopropanol gel dosimeter. Both the co-solvent free and isopropanol solvent gel dosimeters have lower effective atomic numbers than water, differing by 2.2% and 6.5%, respectively. As a result, their photoelectric absorption interaction probabilities are up to 6% and 19% different from water, respectively. Compton scattering and pair production interaction probabilities of NIPAM gel with isopropanol differ by up to 10% from water while for the co-solvent free gel, the differences are 3%. Mass attenuation and energy absorption coefficients of the co-solvent free gel dosimeter and the isopropanol gel dosimeter are up to 7% and 19% lower than water, respectively. Collisional and total mass stopping powers of both gel dosimeters differ by less than 2% from those of water. The dose response of the co-solvent free gel dosimeter is water equivalent (with <1% discrepancy) for dosimetry of x-rays with energies <100 keV while the discrepancy increases (up to 5%) for the isopropanol gel dosimeter over the same energy range. For x-ray beams over the energy range 180 keV-18 MV, both gel dosimeters have less than 2% discrepancy with water. For megavoltage electron beams, the dose differences with water reach 7% and 14% for the co-solvent free gel dosimeter and the isopropanol gel dosimeter, respectively. Our results demonstrate that for x-ray beam dosimetry with photon energies higher than 100 keV and megavoltage electron beams, correction factors are needed for both NIPAM gels to be used as water equivalent dosimeters.
Calibration of a turbidity meter for making estimates of total suspended solids concentrations and beam attenuation coefficients in field experiments
NASA Technical Reports Server (NTRS)
Usry, J. W.; Whitlock, C. H.
Management of water resources such as a reservoir requires using analytical models which describe such parameters as the suspended sediment field. To select or develop an appropriate model requires making many measurements to describe the distribution of this parameter in the water column. One potential method for making those measurements expeditiously is to measure light transmission or turbidity and relate that parameter to total suspended solids concentrations. An instrument which may be used for this purpose was calibrated by generating curves of transmission measurements plotted against measured values of total suspended solids concentrations and beam attenuation coefficients. Results of these experiments indicate that field measurements made with this instrument using curves generated in this study should correlate with total suspended solids concentrations and beam attenuation coefficients in the water column within 20 percent.
X-ray transmission through a plasma window
B. T. Pinkoski; I. Zacharia; A. Hershcovitch; E. D. Johnson; D. P. Siddons
Traditional solid window materials used for x-ray synchrotron beamlines may introduce undesirably high attenuation, or are subject to failure under high heat loads. A plasma window can in principle obviate these problems over a wide range of energies. Experiments were performed at the Brookhaven National Laboratory National Synchrotron Light Source on beamline X6A to study the transmission characteristics of a
Derivation of total diffuse attenuation coefficient from water column temperature data and meteorological water surface fluxes: A simple management tool
Sri Adiyanti; J÷rg Imberger
The total diffuse attenuation coefficient of Photosynthetically Available Radiation (Kd(PAR)) is derived by optimising the solution of a surface layer model to match temperature profiles measured with a precision thermistor chain; a non?linear least?squares Levenberg?Marquardt scheme is applied to optimize Kd(PAR). The method was validated in Lake Kinneret (Israel) over 10 days in summer to early winter 2001, Valle de
Measurement of the mass attenuation coefficients of Ge and BGO for high-energy gamma-rays
Hideo Harada; Fumito Kitatani; Kaoru Y. Hara; Hiroyuki Toyokawa; Takeshi Kaihori; Hiroaki Utsunomiya
The gamma-ray mass attenuation coefficients of important materials for gamma-ray detection have been measured using the laser-Compton backscattering gamma-rays (LCS gamma-rays) and the high-resolution high-energy photon spectrometer (HHS). The preliminary results performed for materials (Ge and BGO) are presented for gamma-ray energy of 5.1 MeV. The measured data are compared with tabulated theoretical calculations.
Determination of mass attenuation coefficients of some boron ores at 59.54keV by using scintillation detector.
Demir, Faruk
The mass attenuation coefficients of the 59.54keV radiation of (241)Am point source in boron ores such as tincal, ulexite and colemanite were determined experimentally by a scintillation detector and theoretically. Since boron ores contain boron, hydrogen, and a lot of elements, they may be used as shielding against neutrons and gammas simultaneously, e.g. for shielding (241)Am/Be neutron sources, as they emit both gammas and neutrons. PMID:19800806
Not Available
This report discusses the following topics: Center for X-Ray Optics; Soft X-Ray Imaging wit Zone Plate Lenses; Biological X-Ray microscopy; Extreme Ultraviolet Lithography for Nanoelectronic Pattern Transfer; Multilayer Reflective Optics; EUV/Soft X-ray Reflectometer; Photoemission Microscopy with Reflective Optics; Spectroscopy with Soft X-Rays; Hard X-Ray Microprobe; Coronary Angiography; and Atomic Scattering Factors.
Trebes, James E. (Livermore, CA); Bell, Perry M. (Tracy, CA); Robinson, Ronald B. (Modesto, CA)
A miniature x-ray source utilizing a hot filament cathode. The source has a millimeter scale size and is capable of producing broad spectrum x-ray emission over a wide range of x-ray energies. The miniature source consists of a compact vacuum tube assembly containing the hot filament cathode, an anode, a high voltage feedthru for delivering high voltage to the cathode, a getter for maintaining high vacuum, a connector for initial vacuum pump down and crimp-off, and a high voltage connection for attaching a compact high voltage cable to the high voltage feedthru. At least a portion of the vacuum tube wall is fabricated from highly x-ray transparent materials, such as sapphire, diamond, or boron nitride.
NASA Technical Reports Server (NTRS)
Grant, P. A.; Jackson, J. W., Jr.; Alcorn, G. E.; Marshall, F. E. (inventors)
An X-ray spectrometer for providing imaging and energy resolution of an X-ray source is described. This spectrometer is comprised of a thick silicon wafer having an embedded matrix or grid of aluminum completely through the wafer fabricated, for example, by thermal migration. The aluminum matrix defines the walls of a rectangular array of silicon X-ray detector cells or pixels. A thermally diffused aluminum electrode is also formed centrally through each of the silicon cells with biasing means being connected to the aluminum cell walls and causes lateral charge carrier depletion between the cell walls so that incident X-ray energy causes a photoelectric reaction within the silicon producing collectible charge carriers in the form of electrons which are collected and used for imaging.
Anne Sakdinawat; David Attwood
Recent years have seen significant progress in the field of soft- and hard-X-ray microscopy, both technically, through developments in source, optics and imaging methodologies, and also scientifically, through a wide range of applications. While an ever-growing community is pursuing the extensive applications of today's available X-ray tools, other groups are investigating improvements in techniques, including new optics, higher spatial resolutions,
X-ray astronomical spectroscopy
NASA Technical Reports Server (NTRS)
Holt, S. S.
The current status of the X-ray spectroscopy of celestial X-ray sources, ranging from nearby stars to distant quasars, is reviewed. Particular emphasis is placed on the role of such spectroscopy as a useful and unique tool in the elucidation of the physical parameters of the sources. The spectroscopic analysis of degenerate and nondegenerate stellar systems, galactic clusters and active galactic nuclei, and supernova remnants is discussed.
NASA Astrophysics Data System (ADS)
The primary advantage of the X-ray computed tomography (XRCT) NDE method is that features are not superposed in the image, thereby rendering them easier to interpret than radiographic projection images. Industrial XRCT systems, unlike medical diagnostic systems, have no size and dosage constraints; they are accordingly used for systems from the scale of gas turbine blades, with hundreds-of-kV energies, to those of the scale of ICBMs, requiring MV-level X-ray energies.
E. Landahl; D. Reis; J. Wang; L. Young
The report discusses the exciting times for short pulse X-rays and the current users of the technology in the United States. Tracking nuclear motions with X-rays transcends scientific disciplines and includes Biology, Materials Science, Condensed Matter and Chemistry. 1 picosecond accesses many phenomena previously hidden at 100ps. Synchrotron advantage over laser plasma and LCLS is that it's easily tunable. There
Tokamak x ray diagnostic instrumentation
Hill, K.W.; Beiersdorfer, P.; Bitter, M.; Fredrickson, E.; Von Goeler, S.; Hsuan, H.; Johnson, L.C.; Liew, S.L.; McGuire, K.; Pare, V.
Three classes of x-ray diagnostic instruments enable measurement of a variety of tokamak physics parameters from different features of the x-ray emission spectrum. (1) The soft x-ray (1 to 50 keV) pulse-height-analysis (PHA) diagnostic measures impurity concentrations from characteristic line intensities and the continuum enhancement, and measures the electron temperature from the continuum slope. (2) The Bragg x-ray crystal spectrometer (XCS) measures the ion temperature and neutral-beam-induced toroidal rotation velocity from the Doppler broadening and wavelength shift, respectively, of spectral lines of medium-Z impurity ions. Impurity charge state distributions, precise wavelengths, and inner-shell excitation and recombination rates can also be studied. X rays are diffracted and focused by a bent crystal onto a position-sensitive detector. The spectral resolving power E/..delta..E is greater than 10/sup 4/ and time resolution is 10 ms. (3) The x-ray imaging system (XIS) measures the spatial structure of rapid fluctuations (0.1 to 100 kHZ) providing information on MHD phenomena, impurity transport rates, toroidal rotation velocity, plasma position, and the electron temperature profile. It uses an array of silicon surface-barrier diodes which view different chords of the plasma through a common slot aperture and operate in current (as opposed to counting) mode. The effectiveness of shields to protect detectors from fusion-neutron radiation effects has been studied both theoretically and experimentally.
NASA Technical Reports Server (NTRS)
Mccammon, D.; Cox, D. P.; Kraushaar, W. L.; Sanders, W. T.
A progress report of research activities carried out in the area of cosmic X-ray physics is presented. The Diffuse X-ray Spectrometer DXS which has been flown twice as a rocket payload is described. The observation times proved to be too small for meaningful X-ray data to be obtained. Data collection and reduction activities from the Ultra-Soft X-ray background (UXT) instrument are described. UXT consists of three mechanically-collimated X-ray gas proportional counters with window/filter combinations which allow measurements in three energy bands, Be (80-110 eV), B (90-187 eV), and O (e84-532 eV). The Be band measurements provide an important constraint on local absorption of X-rays from the hot component of the local interstellar medium. Work has also continued on the development of a calorimetric detector for high-resolution spectroscopy in the 0.1 keV - 8keV energy range.
NASA Astrophysics Data System (ADS)
Hartley, Frank T.; Khan Malek, Chantal G.
New developments for x-ray nanomachining include pattern transfer onto non-planar surfaces coated with electrodeposited resists using synchrotron radiation x-rays through extremely high-resolution mask made by chemically assisted focused ion beam lithography. Standard UV photolithographic processes cannot maintain sub-micron definitions over large variation in feature topography. The ability of x-ray printing to pattern thin or thick layers of photoresist with high resolution on non-planar surfaces of large and complex topographies with limited diffraction and scattering effects and no substrate reflection is known and can be exploited for patterning microsystems with non-planar 3D geometries as well as multisided and multilayered substrates. Thin conformal coatings of electro-deposited positive and negative tone photoresist have been shown to be x-ray sensitive and accommodate sub-micro pattern transfer over surface of extreme topographical variations. Chemically assisted focused ion beam selective anisotropic erosion was used to fabricate x-ray masks directly. Masks with feature sizes less than 20 nm through 7 microns of gold were made on bulk silicon substrates and x-ray mask membranes. The technique is also applicable to other high density materials. Such masks enable the primary and secondary patterning and/or 3D machining of Nano-Electro-Mechanical Systems over large depths or complex relief and the patterning of large surface areas with sub-optically dimensioned features.
Nonlinear refraction of hard x rays
Fratalocchi, A. [Research Center Enrico Fermi, Via Panisperna 89/A, I-00184 Roma (Italy); Research Center SOFT INFM-CNR, c/o University of Rome 'Sapienza', I-00185 Roma (Italy); Conti, C. [Research Center SOFT INFM-CNR, c/o University of Rome 'Sapienza', I-00185 Roma (Italy); Ruocco, G. [Research Center SOFT INFM-CNR, c/o University of Rome 'Sapienza', I-00185 Roma (Italy); Department of Physics, University of Rome 'Sapienza', I-00185 Roma (Italy); Sette, F. [European Synchrotron Radiation Facility, Boite Postale 220, 38043 Grenoble (France)
We study the nonlinear refraction of x rays in highly ionized condensed matter by using a classical model of a cold electron plasma in a lattice of still ions coupled with Maxwell equations. By employing a group-theoretical technique, we reduce the governing equations of the system to an integrable set of nonlinear ordinary differential equations, discussing the existence and stability of nonlinear waves. This allows us to define the effective Kerr coefficient n{sub 2} at x rays. With reference to real-world crystalline materials (B, C, Li, and Na), we consider beam self-defocusing and predict that nonlinear processes become comparable to the linear ones for focused beams with powers on the order of mc{sup 3}/r{sub 0} ({approx_equal}10 GW), the classical electron power. As a consequence, nonlinear phenomena are expected to largely affect imaging experiments in currently exploited x-ray free-electron lasers and in their future developments.
High Speed Gas Density Measurements Using Proton Induced X-Rays
G. M. Thomson; K. A. Jamison
The need for high speed gas density measurements in interior ballistic environments has led to the development of a technique which uses the attenuation that a gas produces in transiting characteristic x-ray fluxes to determine its density. To assess the technique an apparatus has been constructed that generates K┐ and K?? x-rays by proton impact on metallic targets and subsequently
Improved Algorithms for Accurate Retrieval of UV - Visible Diffuse Attenuation Coefficients in Optically Complex, Inshore Waters
NASA Technical Reports Server (NTRS)
Cao, Fang; Fichot, Cedric G.; Hooker, Stanford B.; Miller, William L.
Photochemical processes driven by high-energy ultraviolet radiation (UVR) in inshore, estuarine, and coastal waters play an important role in global bio geochemical cycles and biological systems. A key to modeling photochemical processes in these optically complex waters is an accurate description of the vertical distribution of UVR in the water column which can be obtained using the diffuse attenuation coefficients of down welling irradiance (Kd()). The Sea UV Sea UVc algorithms (Fichot et al., 2008) can accurately retrieve Kd ( 320, 340, 380,412, 443 and 490 nm) in oceanic and coastal waters using multispectral remote sensing reflectances (Rrs(), Sea WiFS bands). However, SeaUVSeaUVc algorithms are currently not optimized for use in optically complex, inshore waters, where they tend to severely underestimate Kd(). Here, a new training data set of optical properties collected in optically complex, inshore waters was used to re-parameterize the published SeaUVSeaUVc algorithms, resulting in improved Kd() retrievals for turbid, estuarine waters. Although the updated SeaUVSeaUVc algorithms perform best in optically complex waters, the published SeaUVSeaUVc models still perform well in most coastal and oceanic waters. Therefore, we propose a composite set of SeaUVSeaUVc algorithms, optimized for Kd() retrieval in almost all marine systems, ranging from oceanic to inshore waters. The composite algorithm set can retrieve Kd from ocean color with good accuracy across this wide range of water types (e.g., within 13 mean relative error for Kd(340)). A validation step using three independent, in situ data sets indicates that the composite SeaUVSeaUVc can generate accurate Kd values from 320 490 nm using satellite imagery on a global scale. Taking advantage of the inherent benefits of our statistical methods, we pooled the validation data with the training set, obtaining an optimized composite model for estimating Kd() in UV wavelengths for almost all marine waters. This optimized composite set of SeaUVSeaUVc algorithms will provide the optical community with improved ability to quantify the role of solar UV radiation in photochemical and photobiological processes in the ocean.
The Physics Analysis of a Gas Attenuator with Argon as a Working Gas
Ryutov,, D.D.
A gas attenuator is an important element of the LCLS facility. The attenuator must operate in a broad range of x-ray energies, provide attenuation coefficient between 1 and 10{sup 4} with the accuracy of 1% and, at the same time, be reliable and allow for many months of un-interrupted operation. S. Shen has recently carried out a detailed design study of the attenuator based on the use of nitrogen as a working gas. In this note we assess the features of the attenuator based on the use of argon. We concentrate on the physics issues, not the design features.
X-ray spectra of galactic X-ray sources
NASA Technical Reports Server (NTRS)
Holt, S. S.
The spectroscopic properties of the various classes of Galactic X-ray sources are discussed, with particular emphasis on binary sources containing an accreting compact object, where post-emission scattering in an accretion disk often prevents the initially produced X-radiation from being observed directly. Theoretical interpretations and X-ray observations are considered for the cataclysmic variables, binary systems with a white dwarf as the compact object and which suffer relatively less from Thomson scattering, and the similar phenomenological spectral characteristics of the bulge sources, including soft transients, bursters and steady X-ray sources with thermal spectra, thought to represent an accreting neutron star, are pointed out. The spectral characteristics of X-ray pulsars in accreting binary systems (rather than the Crab pulsar, which is losing rotational kinetic energy with time) are then presented and interpreted in terms of accretion in the polar regions, and mechanisms for the newly discovered X-ray emission from late-type RS CVn stars are considered.
Cooled window for X-rays or charged particles
Logan, C.M.
A window is disclosed that provides good structural integrity and a very high capacity for removal of the heat deposited by x-rays, electrons, or ions, with minimum attenuation of the desired beam. The window is cooled by providing microchannels therein through which a coolant is pumped. For example, the window may be made of silicon with etched microchannels therein and covered by a silicon member. A window made of silicon with a total thickness of 520 {micro}m transmits 96% of the x-rays at an energy of 60 keV, and the transmission is higher than 90% for higher energy photons. 1 fig.
The Physics of the Gas Attenuator for the Linac Coherent Light Source (LCLS)
Ryutov, D.D.; Bionta, R.M.; Hau-Riege, S.P.; Kishiyama, K.I.; McMahon, D.; Roeben, M.D.; Shen, S.; /LLNL, Livermore; Stefan, P.M.; /SLAC; ,
A systematic assessment of a variety of physics issues affecting the performance of the LCLS X-ray beam attenuator is presented. Detailed analysis of the gas flow in the gas attenuator and in the apertures is performed. A lot of attention is directed towards the gas ionization and heating by intense X-ray pulses. The role of these phenomena in possible deviations of the attenuation coefficient from its 'dialed in' value is evaluated and found small in most cases. Other sources of systematic and statistical errors are also discussed. The regimes where the errors may reach a few percent correspond to the lower X-ray energies (less than 2 keV) and highest beam intensities. Other effects discussed include chemical interaction of the gas with apertures, shock formation in the transonic flow in the apertures of the attenuator, generation of electromagnetic wakes in the gas, and head-to-tail variation of the attenuation caused by the ionization of gas or solid. Possible experimental tests of the consistency of the physics assumptions used in the concept of the gas attenuator are discussed. Interaction of X-rays with the solid attenuator (that will be used at higher X-ray energies, from 2.5 to 8 keV) is considered and thermo-mechanical effects caused by the beam heating are evaluated. Wave-front distortions induced by non-uniform heating of both the solid and the gas are found to be small. An overall conclusion drawn from the analysis presented is that the attenuator will be a reliable and highly versatile device, provided that some caution is exercised in its use for highest beam intensities at lowest X-ray energies.
George Neil
Since before the scattering of X-rays off of DNA led to the first understanding of the double helix structure, sources of X-rays have been an essential tool for scientists examining the structure and interactions of matter. The resolution of a microscope is proportional to the wavelength of light so x-rays can see much finer structures than visible light, down to single atoms. In addition, the energy of X-rays is resonant with the core atomic levels of atoms so with appropriate wavelengths the placement of specific atoms in a large molecule can be determined. Over 10,000 scientists use synchrotron sources, storage rings of high energy electrons, each year worldwide. As an example of such use, virtually every picture of a protein or drug molecule that one sees in the scientific press is a reconstruction based on X-ray scattering of synchrotron light from the crystallized form of that molecule. Unfortunately those pictures are static and proteins work through configuration (shape) changes in response to energy transfer. To understand how biological systems work requires following the energy flow to these molecules and tracking how shape changes drive their interaction with other molecules. We'd like to be able to freeze the action of these molecules at various steps along the way with an X-ray strobe light. How fast does it have to be? To actually get a picture of a molecule in a fixed configuration requires X-ray pulses as short as 30 femtoseconds (1/30 of a millionth of a millionth of a second). To capture the energy flow through changes in electronic levels requires a faster strobe, less than 1 femtosecond! And to acquire such information in smaller samples with higher accuracy demands brighter and brighter X-rays. Unfortunately modern synchrotrons (dubbed 3rd Generation Light Sources) cannot deliver such short bright pulses of X-rays. An entirely new approach is required, linear-accelerator (linac-)-based light sources termed 4th or Next Generation Light Sources (NGLSs). Although NGLSs will not displace synchrotrons from their role they do offer exciting new capabilities which can be understood from the physics of the light production in each device.
Optimization of phosphor screens for charge coupled device based detectors and 7{endash}34 keV x-rays
Wang, P.; Cargill, G.S. III [Department of Chemical Engineering, Materials Science and Mining Engineering, Columbia University, New York, New York 10027 (United States)] [Department of Chemical Engineering, Materials Science and Mining Engineering, Columbia University, New York, New York 10027 (United States)
Phosphor screens convert x-ray images to visible light images in two-dimensional charge coupled device (CCD) based detector systems used for x-ray diffraction. Some experimental and theoretical aspects of phosphor screen performance are described in this article. The efficiencies of x-ray-to-light conversion were measured using a CCD camera for transmission phosphor screens fabricated from two different phosphor powders, Y{sub 2}O{sub 2}S:Eu (P22R) and Gd{sub 2}O{sub 2}S:Tb (P43), for screen mass thicknesses of 3{endash}50 mg/cm{sup 2} and for x-ray energies of 7{endash}34 keV. A model was developed and evaluated for the dependence of the emitted light brightness on screen thickness and x-ray energy. Inputs to the model are x-ray absorption coefficients and light attenuation versus thickness data, which were determined experimentally for the phosphors and found to be dominated by scattering rather than absorption. The angular distribution of emitted light, was found to be nearly Lambertian. Broadening of image features in the x-ray-to-visible-light conversion by phosphors for 19.6 keV x-rays was found to increase approximately linearly with phosphor screen thicknesses in the range of 30{endash}160 {mu}m, but with a minimum width of 110 {mu}m for P22R phosphor and 70 {mu}m for P43 phosphor. In the range of 7{endash}15 keV, maximum brightness was obtained for P43 phosphor screens of about 10 mg/cm{sup 2} mass thickness (60 {mu}m). For P22R screens, the thickness for maximum brightness increased from about 8 mg/cm{sup 2} (50 {mu}m) for 7 keV to more than 46 mg/cm{sup 2} (210 {mu}m) for 15 keV. For 7 keV the maximum brightnesses for P22R and P43 phosphors were about the same. For 10 keV the maximum brightness for P43 phosphor was about 60{percent} greater than the maximum brightness for P22R phosphor samples tested. For 15 keV the maximum brightness for P43 phosphor was again about 60{percent} greater than that for the P22R samples tested. (Abstract Truncated)
Photon attenuation coefficients of Heavy-Metal Oxide glasses by MCNP code, XCOM program and experimental data: A comparison study
NASA Astrophysics Data System (ADS)
El-Khayatt, A. M.; Ali, A. M.; Singh, Vishwanath P.
The mass attenuation coefficients, ?/?, total interaction cross-section, ?t, and mean free path (MFP) of some Heavy Metal Oxides (HMO) glasses, with potential applications as gamma ray shielding materials, have been investigated using the MCNP-4C code. Appreciable variations are noted for all parameters by changing the photon energy and the chemical composition of HMO glasses. The numerical simulations parameters are compared with experimental data wherever possible. Comparisons are also made with predictions from the XCOM program in the energy region from 1 keV to 100 MeV. Good agreement noticed indicates that the chosen Monte Carlo method may be employed to make additional calculations on the photon attenuation characteristics of different glass systems, a capability particularly useful in cases where no analogous experimental data exist.
NASA Technical Reports Server (NTRS)
Kallman, T. R.; Mccray, R.
Theoretical models are presented for the temperature and ionization structure of spherically symmetric, constant density, gaseous nebulae surrounding compact X-ray sources and for the optical, UV, and X-ray spectra emerging from the nebulae. The structure is determined by assuming a local balance between heating and cooling in the gas, and the radiation field is found by solving a simplified equation of transfer. The calculations include an accurate and comprehensive treatment of the atomic processes affecting the state of the gas and the radiation field. The destruction of line radiation during resonance scattering causes models to be significantly hotter and more highly ionized than previous models of the same type. Model results are presented for a wide variety of gas densities and X-ray source spectra, scaling laws which allow these results to be generalized to a wide variety of astrophysical solutions are discussed, and column densities of multiply charged species are tabulated.
X-ray exposure sensor and controller
NASA Technical Reports Server (NTRS)
Berdahl, C. Martin (Inventor)
An exposure controller for x-ray equipment is provided, which comprises a portable and accurate sensor which can be placed adjacent to and directly beneath the area of interest of an x-ray plate, and which measures the amount of exposure received by that area, and turns off the x-ray equipment when the exposure for the particular area of interest on the x-ray plate reaches the value which provides an optimal x-ray plate.
TOPICAL REVIEW: Human soft tissue analysis using x-ray or gamma-ray techniques
NASA Astrophysics Data System (ADS)
Theodorakou, C.; Farquharson, M. J.
This topical review is intended to describe the x-ray techniques used for human soft tissue analysis. X-ray techniques have been applied to human soft tissue characterization and interesting results have been presented over the last few decades. The motivation behind such studies is to provide improved patient outcome by using the data obtained to better understand a disease process and improve diagnosis. An overview of theoretical background as well as a complete set of references is presented. For each study, a brief summary of the methodology and results is given. The x-ray techniques include x-ray diffraction, x-ray fluorescence, Compton scattering, Compton to coherent scattering ratio and attenuation measurements. The soft tissues that have been classified using x-rays or gamma rays include brain, breast, colon, fat, kidney, liver, lung, muscle, prostate, skin, thyroid and uterus.
Measurements of the thermal coefficient of optical attenuation at different depth regions of in vivo human skins using optical coherence tomography: a pilot study
Su, Ya; Yao, X. Steve; Li, Zhihong; Meng, Zhuo; Liu, Tiegen; Wang, Longzhi
We present detailed measurement results of optical attenuationÆs thermal coefficients (referenced to the temperature of the skin surface) in different depth regions of in vivo human forearm skins using optical coherence tomography (OCT). We first design a temperature control module with an integrated optical probe to precisely control the surface temperature of a section of human skin. We propose a method of using the correlation map to identify regions in the skin having strong correlations with the surface temperature of the skin and find that the attenuation coefficient in these regions closely follows the variation of the surface temperature without any hysteresis. We observe a negative thermal coefficient of attenuation in the epidermis. While in dermis, the slope signs of the thermal coefficient of attenuation are different at different depth regions for a particular subject, however, the depth regions with a positive (or negative) slope are different in different subjects. We further find that the magnitude of the thermal coefficient of attenuation coefficient is greater in epidermis than in dermis. We believe the knowledge of such thermal properties of skins is important for several noninvasive diagnostic applications, such as OCT glucose monitoring, and the method demonstrated in this paper is effective in studying the optical and biological properties in different regions of skin. PMID:25780740
Compact x-ray source and panel
Sampayon, Stephen E. (Manteca, CA)
A compact, self-contained x-ray source, and a compact x-ray source panel having a plurality of such x-ray sources arranged in a preferably broad-area pixelized array. Each x-ray source includes an electron source for producing an electron beam, an x-ray conversion target, and a multilayer insulator separating the electron source and the x-ray conversion target from each other. The multi-layer insulator preferably has a cylindrical configuration with a plurality of alternating insulator and conductor layers surrounding an acceleration channel leading from the electron source to the x-ray conversion target. A power source is connected to each x-ray source of the array to produce an accelerating gradient between the electron source and x-ray conversion target in any one or more of the x-ray sources independent of other x-ray sources in the array, so as to accelerate an electron beam towards the x-ray conversion target. The multilayer insulator enables relatively short separation distances between the electron source and the x-ray conversion target so that a thin panel is possible for compactness. This is due to the ability of the plurality of alternating insulator and conductor layers of the multilayer insulators to resist surface flashover when sufficiently high acceleration energies necessary for x-ray generation are supplied by the power source to the x-ray sources.
Applications of Hard X-ray Full-Field Transmission X-ray Microscopy at SSRL
Liu, Y.; Andrews, J. C.; Mehta, A.; Pianetta, P. [Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, CA 94025 (United States); Meirer, F. [Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, CA 94025 (United States); MiNALab, CMM-Irst, Fondazione Bruno Kessler, Via Sommarive 18, 38123 Povo, Trento (Italy); Gil, S. Carrasco [CIEMAT, Avda Complutense 22, MADRID 28040 (Spain); Sciau, P. [CEMES (UPR 8011 CNRS), 29 rue J. Marvig, 31055 Toulouse Cedex 4 (France); Mester, Z. [Institute for National Measurement Standards, National Research Council, Ottawa ON K1A0R6 (Canada)
State-of-the-art hard x-ray full-field transmission x-ray microscopy (TXM) at beamline 6-2C of Stanford Synchrotron Radiation Lightsource has been applied to various research fields including biological, environmental, and material studies. With the capability of imaging a 32-micron field-of-view at 30-nm resolution using both absorption mode and Zernike phase contrast, the 3D morphology of yeast cells grown in gold-rich media was investigated. Quantitative evaluation of the absorption coefficient was performed for mercury nanoparticles in alfalfa roots exposed to mercury. Combining XANES and TXM, we also performed XANES-imaging on an ancient pottery sample from the Roman pottery workshop at LaGraufesenque (Aveyron).
X-Ray Tomography: The Ultimate Petrographic Tool for Studying Pumice
NASA Astrophysics Data System (ADS)
Gualda, G. A.; Pamukcu, A. S.; Rivers, M. L.
Over the last several years, we have been studying pumice from large-volume tuffs using synchrotron-based x- ray computed microtomography. Our goal is to document in detail and quantitatively crystal and bubble textures in pumice to retrieve information on the evolution of giant magma bodies over time, particularly for the stages leading to supereruptions. X-ray tomography yields 3D maps of x-ray linear attenuation coefficients, allowing documentation and visualization of textures in 3D, with resolution down to micrometer scale or better. X-ray tomography is ideal for the study of pumice, where crystals are sparse and mostly separated from each other by low-density vesicular glass. This is particularly fortunate because (a) pumice is poorly suited to being studied using thin-sections due to the low abundance of crystals, and (b) stereological corrections are unnecessary. Imaging is non-destructive, can be performed quickly (minutes to hours), and with little or no sample preparation. X-ray tomography is the perfect complement to physical separation methods (e.g. crushing, sieving and winnowing), which do allow extraction of individual crystals for detailed study, but also cause crystal breakage and yield little to no information on the vesicle populations. The application of x-ray tomography to pumice from the Bishop Tuff (California) and Peach Spring Tuff (Nevada-Arizona-California) reveals that, at the energies of interest, contrasts in attenuation are such that resulting tomograms enable the distinction of at least 5-6 of the most abundant phases present (i.e. void space, glass, quartz, feldspar, 1-2 mafic minerals, oxides). Using differential absorption x-ray tomography, we can map the distribution of key chemical elements in 3D, notably Zr and Ce, allowing the unambiguous identification and quantification of the sizes and spatial distribution of important accessory minerals such as zircon, titanite, and allanite (▒ chevkinite), for which textural information is almost completely lacking. Study of pumice from the Bishop Tuff shows that: (1) crystal fragmentation is an important magmatic process, with fragment size distributions following power laws typical of fractal processes; (2) quartz + feldspar crystal size distributions reveal two distinct crystal populations, one formed by crystallization under low supersaturation over millennial timescales, and another formed under high supersaturation (possibly reflecting decompression crystallization) within the final years to months before eruption; (3) a large vesicle with >50 magnetite crystals attached to its wall likely represents the first textural evidence for the presence of pre-eruptive bubbles in Bishop magma; (4) it may be possible to retrieve information on the pre-and syn-eruptive bubble populations from the study of vesicle size distributions. Study of pumice from the Peach Spring Tuff using Zr and Ce maps reveals that, surprisingly, most of the zircon crystals are included in large titanite crystals (also attached to allanite), while only a small number of zircon crystals occur isolated within the glassy matrix. This suggests that different zircon crystals may record different aspects of the crystallization history of pumice. Our ongoing studies of pumice from the Bishop and Peach Spring Tuff show that, especially when combined to crystal chemistry information, x-ray tomography provides invaluable information on the evolution of magmatic systems, with unprecedented level of detail.
Optimized Volumetric Scanning for X-Ray Array Sources
Lehman, S K; Foudray, A M; Wang, A; Kallman, J S; Martz, H
Non-destructive evaluation (NDE) is the science and technology of determining non-invasively the internal structure of manufactured parts, objects, and materials. NDE application areas include medicine, industrial manufacturing, military, homeland security, and airport luggage screening. X-ray measurement systems are most widely used because of their ability to image through a wide range of material densities (from human tissue in medical applications to the dense materials of weapon components). Traditional x-ray systems involve a single source and detector system that rotate and/or translate about the object under evaluation. At each angular location, the source projects x-rays through the object. The rays undergo attenuation proportional to the density of the object's constitutive material. The detector records a measure of the attenuation. Mathematical algorithms are used to invert the forward attenuated ray projection process to form images of the object. This is known as computed tomography (CT). In recent years, the single-source x-ray NDE systems have been generalized to arrays of x-ray sources. Array sources permit multiple views of the object with fewer rotations and translations of the source/detector system. The spatially diverse nature of x-ray array sources has the potential of reducing data collection time, reducing imaging artifacts, and increasing the resolution of the resultant images. Most of the existing CT algorithms were not derived from array source models with a spatially diverse set of viewing perspectives. Single-source x-ray CT data collection, processing, and imaging methods and algorithms are not applicable when the source location is expanded from one dimension (a rotating and/or translating point source) to two (a rotating and/or translating array). They must be reformulated. The goal of this project is to determine the applicability of x-ray array sources to problems of interest to LLNL and its customers. It is believed array source data collection will be faster while yielding higher resolution reconstructions with fewer artifacts. There are three tasks in the research: (1) Develop forward array source analytic and computational models; (2) Research and develop array source reconstruction algorithms; and (3) Perform experiments.
Multi-frequency characterization of the speed of sound and attenuation coefficient for longitudinal transmission of freshly excised human skulls
Pichardo, Samuel; Sin, Vivian W; Hynynen, Kullervo
For medical applications of ultrasound inside the brain, it is necessary to understand the relationship between the apparent density of skull bone and its corresponding speed of sound and attenuation coefficient. Although there have been previous studies exploring this phenomenon, there is still a need to extend the measurements to cover more of the clinically relevant frequency range. The results of measurements of the longitudinal speed of sound and attenuation coefficient are presented for specimens of human calvaria. The study was performed for the frequencies of 0.27, 0.836, 1.402, 1.965 and 2.525 MHz. Specimens were obtained from fresh cadavers through a protocol with the Division of Anatomy of the University of Toronto. The protocol was approved by the Research Ethics Board of Sunnybrook Health Sciences Centre. The specimens were mounted in polycarbonate supports that were marked for stereoscopic positioning. Computer tomography (CT) scans of the skulls mounted on their supports were performed, and a three-dimensional skull surface was reconstructed. This surface was used to guide a positioning system to ensure the normal sound incidence of an acoustic signal. This signal was produced by a focused device with a diameter of 5 cm and a focal length of 10 cm. Measurements of delay in time of flight were carried out using a needle hydrophone. Measurements of effective transmitted energy were carried out using a radiation force method with a 10 ?g resolution scale. Preliminary functions of speed of sound and attenuation coefficient, both of which are related to apparent density, were established using a multi-layer propagation model that takes into account speed of sound, density and thickness of the layer. An optimization process was executed from a large set of random functions and the best functions were chosen for those ones that closest reproduced the experimental observations. The final functions were obtained after a second pass of the optimization process was executed, but this time using a finite-difference time-difference solution of the Westervelt equation, which is more precise than the multi-layer model but much more time consuming for computation. For six of seven specimens, measurements were carried out on five locations on the calvaria, and for the other specimen three measurements were made. In total, measurements were carried out on 33 locations. Results indicated the presence of dispersion effects and that these effects are different according to the type of bone in the skull (cortical and trabecular). Additionally, both the speed of sound and attenuation showed dependence on the skull density that varied with the frequency. Using the optimal functions and the information of density from the CT scans, the average values (▒s.d.) of the speed of sound for cortical bone were estimated to be 2384(▒130), 2471(▒90), 2504(▒120), 2327(▒90) and 2053(▒40) m s?1 for the frequencies of 270, 836, 1402, 1965 and 2526 kHz, respectively. For trabecular bone, and in the same order of frequency values, the speeds of sound were 2140(▒130), 2300(▒100), 2219(▒200), 2133(▒130) and 1937(▒40) m s?1, respectively. The average values of the attenuation coefficient for cortical bone were 33(▒9), 240(▒9) and 307(▒30) Np m?1 for the frequencies of 270, 836, and 1402, respectively. For trabecular bone, and in the same order of frequency values, the average values of the attenuation coefficient were 34(▒13), 216(▒16) and 375(▒30) Np m?1, respectively. For frequencies of 1.965 and 2.525 MHz, no measurable radiation force was detected with the setup used. PMID:21149950
Multi-frequency characterization of the speed of sound and attenuation coefficient for longitudinal transmission of freshly excised human skulls
NASA Astrophysics Data System (ADS)
Pichardo, Samuel; Sin, Vivian W.; Hynynen, Kullervo
For medical applications of ultrasound inside the brain, it is necessary to understand the relationship between the apparent density of skull bone and its corresponding speed of sound and attenuation coefficient. Although there have been previous studies exploring this phenomenon, there is still a need to extend the measurements to cover more of the clinically relevant frequency range. The results of measurements of the longitudinal speed of sound and attenuation coefficient are presented for specimens of human calvaria. The study was performed for the frequencies of 0.27, 0.836, 1.402, 1.965 and 2.525 MHz. Specimens were obtained from fresh cadavers through a protocol with the Division of Anatomy of the University of Toronto. The protocol was approved by the Research Ethics Board of Sunnybrook Health Sciences Centre. The specimens were mounted in polycarbonate supports that were marked for stereoscopic positioning. Computer tomography (CT) scans of the skulls mounted on their supports were performed, and a three-dimensional skull surface was reconstructed. This surface was used to guide a positioning system to ensure the normal sound incidence of an acoustic signal. This signal was produced by a focused device with a diameter of 5 cm and a focal length of 10 cm. Measurements of delay in time of flight were carried out using a needle hydrophone. Measurements of effective transmitted energy were carried out using a radiation force method with a 10 Ąg resolution scale. Preliminary functions of speed of sound and attenuation coefficient, both of which are related to apparent density, were established using a multi-layer propagation model that takes into account speed of sound, density and thickness of the layer. An optimization process was executed from a large set of random functions and the best functions were chosen for those ones that closest reproduced the experimental observations. The final functions were obtained after a second pass of the optimization process was executed, but this time using a finite-difference time-difference solution of the Westervelt equation, which is more precise than the multi-layer model but much more time consuming for computation. For six of seven specimens, measurements were carried out on five locations on the calvaria, and for the other specimen three measurements were made. In total, measurements were carried out on 33 locations. Results indicated the presence of dispersion effects and that these effects are different according to the type of bone in the skull (cortical and trabecular). Additionally, both the speed of sound and attenuation showed dependence on the skull density that varied with the frequency. Using the optimal functions and the information of density from the CT scans, the average values (▒s.d.) of the speed of sound for cortical bone were estimated to be 2384(▒ 130), 2471(▒ 90), 2504(▒ 120), 2327(▒ 90) and 2053(▒ 40) m s-1 for the frequencies of 270, 836, 1402, 1965 and 2526 kHz, respectively. For trabecular bone, and in the same order of frequency values, the speeds of sound were 2140(▒ 130), 2300(▒ 100), 2219(▒ 200), 2133(▒ 130) and 1937(▒ 40) m s-1, respectively. The average values of the attenuation coefficient for cortical bone were 33(▒ 9), 240(▒ 9) and 307(▒ 30) Np m-1 for the frequencies of 270, 836, and 1402, respectively. For trabecular bone, and in the same order of frequency values, the average values of the attenuation coefficient were 34(▒ 13), 216(▒ 16) and 375(▒ 30) Np m-1, respectively. For frequencies of 1.965 and 2.525 MHz, no measurable radiation force was detected with the setup used.
Prospects for in vivo estimation of photon linear attenuation coefficients using postprocessing dual-energy CT imaging on a commercial scanner: Comparison of analytic and polyenergetic statistical reconstruction algorithms
Evans, Joshua D., E-mail: email@example.com; Yu, Yaduo; Williamson, Jeffrey F. [Department of Radiation Oncology, Virginia Commonwealth University, Richmond, Virginia 23298 (United States)] [Department of Radiation Oncology, Virginia Commonwealth University, Richmond, Virginia 23298 (United States); Whiting, Bruce R. [Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania 15213 (United States)] [Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania 15213 (United States); OÆSullivan, Joseph A. [Department of Electrical and Systems Engineering, Washington University, St. Louis, Missouri 63130 (United States)] [Department of Electrical and Systems Engineering, Washington University, St. Louis, Missouri 63130 (United States); Politte, David G. [Mallinckrodt Institute of Radiology, Washington University, St. Louis, Missouri 63110 (United States)] [Mallinckrodt Institute of Radiology, Washington University, St. Louis, Missouri 63110 (United States); Klahr, Paul H. [Philips Healthcare, 595 Miner Rd., Highland Hts., Ohio 44143 (United States)] [Philips Healthcare, 595 Miner Rd., Highland Hts., Ohio 44143 (United States)
Purpose: Accurate patient-specific photon cross-section information is needed to support more accurate model-based dose calculation for low energy photon-emitting modalities in medicine such as brachytherapy and kilovoltage x-ray imaging procedures. A postprocessing dual-energy CT (pDECT) technique for noninvasivein vivo estimation of photon linear attenuation coefficients has been experimentally implemented on a commercial CT scanner and its accuracy assessed in idealized phantom geometries. Methods: Eight test materials of known composition and density were used to compare pDECT-estimated linear attenuation coefficients to NIST reference values over an energy range from 10 keV to 1 MeV. As statistical image reconstruction (SIR) has been shown to reconstruct images with less random and systematic error than conventional filtered backprojection (FBP), the pDECT technique was implemented with both an in-house polyenergetic SIR algorithm, alternating minimization (AM), as well as a conventional FBP reconstruction algorithm. Improvement from increased spectral separation was also investigated by filtering the high-energy beam with an additional 0.5 mm of tin. The law of propagated uncertainty was employed to assess the sensitivity of the pDECT process to errors in reconstructed images. Results: Mean pDECT-estimated linear attenuation coefficients for the eight test materials agreed within 1% of NIST reference values for energies from 1 MeV down to 30 keV, with mean errors rising to between 3% and 6% at 10 keV, indicating that the method is unbiased when measurement and calibration phantom geometries are matched. Reconstruction with FBP and AM algorithms conferred similar mean pDECT accuracy. However, single-voxel pDECT estimates reconstructed on a 1 ū 1 ū 3 mm{sup 3} grid are shown to be highly sensitive to reconstructed image uncertainty; in some cases pDECT attenuation coefficient estimates exhibited standard deviations on the order of 20% around the mean. Reconstruction with the statistical AM algorithm led to standard deviations roughly 40% to 60% less than FBP reconstruction. Additional tin filtration of the high energy beam exhibits similar pDECT estimation accuracy as the unfiltered beam, even when scanning with only 25% of the dose. Using the law of propagated uncertainty, low Z materials are found to be more sensitive to image reconstruction errors than high Z materials. Furthermore, it is estimated that reconstructed CT image uncertainty must be limited to less than 0.25% to achieve a target linear-attenuation coefficient estimation uncertainty of 3% at 28 keV. Conclusions: That pDECT supports mean linear attenuation coefficient measurement accuracies of 1% of reference values for energies greater than 30 keV is encouraging. However, the sensitivity of the pDECT measurements to noise and systematic errors in reconstructed CT images warrants further investigation in more complex phantom geometries. The investigated statistical reconstruction algorithm, AM, reduced random measurement uncertainty relative to FBP owing to improved noise performance. These early results also support efforts to increase DE spectral separation, which can further reduce the pDECT sensitivity to measurement uncertainty.
Prospects for in vivo estimation of photon linear attenuation coefficients using postprocessing dual-energy CT imaging on a commercial scanner: Comparison of analytic and polyenergetic statistical reconstruction algorithms
Evans, Joshua D.; Whiting, Bruce R.; OÆSullivan, Joseph A.; Politte, David G.; Klahr, Paul H.; Yu, Yaduo; Williamson, Jeffrey F.
Purpose: Accurate patient-specific photon cross-section information is needed to support more accurate model-based dose calculation for low energy photon-emitting modalities in medicine such as brachytherapy and kilovoltage x-ray imaging procedures. A postprocessing dual-energy CT (pDECT) technique for noninvasive in vivo estimation of photon linear attenuation coefficients has been experimentally implemented on a commercial CT scanner and its accuracy assessed in idealized phantom geometries. Methods: Eight test materials of known composition and density were used to compare pDECT-estimated linear attenuation coefficients to NIST reference values over an energy range from 10 keV to 1 MeV. As statistical image reconstruction (SIR) has been shown to reconstruct images with less random and systematic error than conventional filtered backprojection (FBP), the pDECT technique was implemented with both an in-house polyenergetic SIR algorithm, alternating minimization (AM), as well as a conventional FBP reconstruction algorithm. Improvement from increased spectral separation was also investigated by filtering the high-energy beam with an additional 0.5 mm of tin. The law of propagated uncertainty was employed to assess the sensitivity of the pDECT process to errors in reconstructed images. Results: Mean pDECT-estimated linear attenuation coefficients for the eight test materials agreed within 1% of NIST reference values for energies from 1 MeV down to 30 keV, with mean errors rising to between 3% and 6% at 10 keV, indicating that the method is unbiased when measurement and calibration phantom geometries are matched. Reconstruction with FBP and AM algorithms conferred similar mean pDECT accuracy. However, single-voxel pDECT estimates reconstructed on a 1 ū 1 ū 3 mm3 grid are shown to be highly sensitive to reconstructed image uncertainty; in some cases pDECT attenuation coefficient estimates exhibited standard deviations on the order of 20% around the mean. Reconstruction with the statistical AM algorithm led to standard deviations roughly 40% to 60% less than FBP reconstruction. Additional tin filtration of the high energy beam exhibits similar pDECT estimation accuracy as the unfiltered beam, even when scanning with only 25% of the dose. Using the law of propagated uncertainty, low Z materials are found to be more sensitive to image reconstruction errors than high Z materials. Furthermore, it is estimated that reconstructed CT image uncertainty must be limited to less than 0.25% to achieve a target linear-attenuation coefficient estimation uncertainty of 3% at 28 keV. Conclusions: That pDECT supports mean linear attenuation coefficient measurement accuracies of 1% of reference values for energies greater than 30 keV is encouraging. However, the sensitivity of the pDECT measurements to noise and systematic errors in reconstructed CT images warrants further investigation in more complex phantom geometries. The investigated statistical reconstruction algorithm, AM, reduced random measurement uncertainty relative to FBP owing to improved noise performance. These early results also support efforts to increase DE spectral separation, which can further reduce the pDECT sensitivity to measurement uncertainty. PMID:24320525
Jez, Joseph M; Blankenship, Robert E
Photosystem II uses metal ions to oxidize water to form O2. Two recent papers employ the new technique of serial femtosecond crystallography utilizing X-ray free-electron lasers and nanocrystals to obtain initial structures of intermediate states of photosystem II catalysis at the site of oxygen production. PMID:25126779
Piestrup, Melvin A. (Woodside, CA); Boyers, David G. (Mountain View, CA); Pincus, Cary I. (Sunnyvale, CA); Maccagno, Pierre (Stanford, CA)
An intense, relatively inexpensive X-ray source (as compared to a synchrotron emitter) for technological, scientific, and spectroscopic purposes. A conical radiation pattern produced by a single foil or stack of foils is focused by optics to increase the intensity of the radiation at a distance from the conical radiator.
NASA Technical Reports Server (NTRS)
Swank, J.
Most of the stellar end-state black holes, pulsars, and white dwarfs that are X-ray sources should have polarized X-ray fluxes. The degree will depend on the relative contributions of the unresolved structures. Fluxes from accretion disks and accretion disk corona may be polarized by scattering. Beams and jets may have contributions of polarized emission in strong magnetic fields. The Gravity and Extreme Magnetism Small Explorer (GEMS) will study the effects on polarization of strong gravity of black holes and strong magnetism of neutron stars. Some part of the flux from compact stars accreting from companion stars has been reflected from the companion, its wind, or accretion streams. Polarization of this component is a potential tool for studying the structure of the gas in these binary systems. Polarization due to scattering can also be present in X-ray emission from white dwarf binaries and binary normal stars such as RS CVn stars and colliding wind sources like Eta Car. Normal late type stars may have polarized flux from coronal flares. But X-ray polarization sensitivity is not at the level needed for single early type stars.
NASA Technical Reports Server (NTRS)
Dennis, Brian; Li, Mary; Skinner, Gerald
X-ray optics were fabricated with the capability of imaging solar x-ray sources with better than 0.1 arcsecond angular resolution, over an order of magnitude finer than is currently possible. Such images would provide a new window into the little-understood energy release and particle acceleration regions in solar flares. They constitute one of the most promising ways to probe these regions in the solar atmosphere with the sensitivity and angular resolution needed to better understand the physical processes involved. A circular slit structure with widths as fine as 0.85 micron etched in a silicon wafer 8 microns thick forms a phase zone plate version of a Fresnel lens capable of focusing approx. =.6 keV x-rays. The focal length of the 3-cm diameter lenses is 100 microns, and the angular resolution capability is better than 0.1 arcsecond. Such phase zone plates were fabricated in Goddard fs Detector Development Lab. (DDL) and tested at the Goddard 600-microns x-ray test facility. The test data verified that the desired angular resolution and throughput efficiency were achieved.
Alpha proton x ray spectrometer
NASA Technical Reports Server (NTRS)
Rieder, Rudi; Waeke, H.; Economou, T.
Mars Pathfinder will carry an alpha-proton x ray spectrometer (APX) for the determination of the elemental chemical composition of Martian rocks and soils. The instrument will measure the concentration of all major and some minor elements, including C, N, and O at levels above typically 1 percent.
Characterization of the ultrasonic attenuation coefficient and its frequency dependence in a polymer gel dosimeter
Remo A. Crescenti; Jeffrey C. Bamber; Mike Partridge; Nigel L. Bush; Steve Webb
Research on polymer-gel dosimetry has been driven by the need for three-dimensional dosimetry, and because alternative dosimeters are unsatisfactory or too slow for that task. Magnetic resonance tomography is currently the most well-developed technique for determining radiation-induced changes in polymer structure, but quick low-cost alternatives remain of significant interest. In previous work, ultrasound attenuation and speed of sound were found
Energy-resolved interferometric x-ray imaging
NASA Astrophysics Data System (ADS)
Pelzer, Georg; Bayer, Florian; G÷del, Karl; Haas, Wilhelm; Horn, Florian; Rieger, Jens; Ritter, Andrķ; Sievers, Peter; Weber, Thomas; Zang, Andrea; Durst, J³rgen; Michel, Thilo; Anton, Gisela
Interferometric X-ray imaging becomes more and more attractive for applications such as medical imaging or non-destructive testing, where a compact setup is needed. Therefore a so-called Talbot-Lau interferometer in combination with a conventional X-ray tube is used. Thereby, three different kinds of images can be obtained. An attenuation image like in conventional X-ray imaging, an image of the differential phase-shifts caused by the object and the so-called dark-field image. The dark-field image shows information about the object's granularity even in sub-pixel dimensions what especially seems very promising for applications like mammography. With respect to optimizing the output of interferometric X-ray imaging in any application, it is inevitable to know the energy response of the interferometer as well as the energy dependence of the interactions of X- rays with matter. In this contribution, simulations and measurements using a Medipix 2 and a Timepix detector are presented.
Modification of the TASMIP x-ray spectral model for the simulation of microfocus x-ray sources
Sisniega, A.; Vaquero, J. J., E-mail: email@example.com [Departamento de BioingenierĒa e IngenierĒa Aeroespacial, Universidad Carlos III de Madrid, Madrid ES28911 (Spain); Instituto de Investigaci¾n Sanitaria Gregorio Mara±¾n, Madrid ES28007 (Spain); Desco, M. [Departamento de BioingenierĒa e IngenierĒa Aeroespacial, Universidad Carlos III de Madrid, Madrid ES28911 (Spain) [Departamento de BioingenierĒa e IngenierĒa Aeroespacial, Universidad Carlos III de Madrid, Madrid ES28911 (Spain); Instituto de Investigaci¾n Sanitaria Gregorio Mara±¾n, Madrid ES28007 (Spain); Centro de Investigaci¾n Biomķdica en Red de Salud Mental (CIBERSAM), Madrid ES28029 (Spain)
Purpose: The availability of accurate and simple models for the estimation of x-ray spectra is of great importance for system simulation, optimization, or inclusion of photon energy information into data processing. There is a variety of publicly available tools for estimation of x-ray spectra in radiology and mammography. However, most of these models cannot be used directly for modeling microfocus x-ray sources due to differences in inherent filtration, energy range and/or anode material. For this reason the authors propose in this work a new model for the simulation of microfocus spectra based on existing models for mammography and radiology, modified to compensate for the effects of inherent filtration and energy range. Methods: The authors used the radiology and mammography versions of an existing empirical model [tungsten anode spectral model interpolating polynomials (TASMIP)] as the basis of the microfocus model. First, the authors estimated the inherent filtration included in the radiology model by comparing the shape of the spectra with spectra from the mammography model. Afterwards, the authors built a unified spectra dataset by combining both models and, finally, they estimated the parameters of the new version of TASMIP for microfocus sources by calibrating against experimental exposure data from a microfocus x-ray source. The model was validated by comparing estimated and experimental exposure and attenuation data for different attenuating materials and x-ray beam peak energy values, using two different x-ray tubes. Results: Inherent filtration for the radiology spectra from TASMIP was found to be equivalent to 1.68Āmm Al, as compared to spectra obtained from the mammography model. To match the experimentally measured exposure data the combined dataset required to apply a negative filtration of about 0.21 mm Al and an anode roughness of 0.003 mm W. The validation of the model against real acquired data showed errors in exposure and attenuation in line with those reported for other models for radiology or mammography. Conclusions: A new version of the TASMIP model for the estimation of x-ray spectra in microfocus x-ray sources has been developed and validated experimentally. Similarly to other versions of TASMIP, the estimation of spectra is very simple, involving only the evaluation of polynomial expressions.
Not Available
The Center for X-Ray Optics has made substantial progress during the past year on the development of very high resolution x-ray technologies, the generation of coherent radiation at x-ray wavelengths, and, based on these new developments, had embarked on several scientific investigations that would not otherwise have been possible. The investigations covered in this report are topics on x-ray sources, x-ray imaging and applications, soft x-ray spectroscopy, synchrotron radiation, advanced light source and magnet structures for undulators and wigglers. (LSP)
Spectral modification of Beer's law and relation to the humidity attenuation coefficient in atmospheric maritime mist
NASA Astrophysics Data System (ADS)
Vul'fson, A. N.
Similarity theory and dimensional analysis are applied to the construction of a relationship for the spectral aerosol extinction coefficient in the visible atmospheric window 0.48 (DOT) 10-4 cm < (lambda) < 0.76 (DOT) 10-4 cm. For maritime mist the results allow one to compare the dependence of the spectral extinction coefficient on humidity as determined in situ with known laboratory observations on the variation in the radius of aerosol particle in moist air. Raoult's modified law is used to show that the variation in the optical properties of soluble aerosol is entirely determined by the variation in the average radius of particles depending on humidity.
X-ray imaging and x-ray source development at Lawrence Livermore National Laboratory
Trebes, J.; Balhorn, R. [Lawrence Livermore National Lab., CA (United States); Anderson, E. [Lawrence Berkeley Lab., CA (United States)] [and others
The Laser Program at Lawrence Livermore National Laboratory has a continuing effort to develop both x-ray sources and x-ray sources and x-ray microscopy. This effort includes the ongoing development of: (1) a wide range of x-ray lasers at the Nova Laser Facility, (2) a zone plate lens--multilayer mirror based x-ray microscope (3) three dimensional, high resolution x-ray microscopy (4) short wavelength, normal incidence multilayer x-ray mirrors, (5) compact, high average power lasers for producing x-ray lasers and laser plasma x-ray sources. We have constructed and operated an x-ray laser based transmission x-ray microscope. The advantage offered by the x-ray laser source is the extreme high brightness allows high resolution images to be made on a timescale faster than that for x-ray damage effects to appear. The microscope, consists of: the x-ray laser, a multilayer coated, near normal incidence spherical mirror used as a condenser, a silicon nitride specimen holder, an x-ray zone plate used as an objective lens, and a microchannel plate x-ray detector. The x-ray laser used is the Ni-like Ta x-ray laser operating with a wavelength of 4.48 nm, a pulselength of 200 spec, a divergence of 10 mrad, and an output energy of 10 microjoules.
X-ray transmission through a plasma window
Pinkoski, B. T.; Zacharia, I.; Hershcovitch, A.; Johnson, E. D.; Siddons, D. P.
Traditional solid window materials used for x-ray synchrotron beamlines may introduce undesirably high attenuation, or are subject to failure under high heat loads. A plasma window can in principle obviate these problems over a wide range of energies. Experiments were performed at the Brookhaven National Laboratory National Synchrotron Light Source on beamline X6A to study the transmission characteristics of a plasma window using argon as the arc gas. Measurements were made around the Ar K edge and far from resonance. The ''white-line'' absorption at the K edge was actually suppressed during arc operation as compared to room temperature gas at the same pressure. This is attributed to the high degree of ionization in the plasma. The relative strength of the white line to the edge jump does not seem to be a strong function of arc current at the argon K edge. Away from resonance ({approx}3 times the edge energy) x-ray attenuation was negligible.
X-ray Tube Using a Graphene Flower Cloth Field Emission Cathode
NASA Astrophysics Data System (ADS)
Iwai, Yusuke; Muramatsu, Kazuo; Tsuboi, Shougo; Jyouzuka, Atsuo; Nakamura, Tomonori; Onizuka, Yoshihiro; Mimura, Hidenori
We have successfully fabricated a filament-less X-ray tube using a graphene flower cloth (GFC) field emission cathode. The GFC has numerous nanoprotrusions formed by self-standing graphene structures. The field emission current and the field enhancement factor ? were 500 ĄA and 5600, respectively. The stability of voltage defined as a variance coefficient (?/mean) of voltage was calculated to be 0.04% while maintaining the X-ray tube current of 300 ĄA. We applied our X-ray tube with the GFC field emitter to the X-ray fluorescence (XRF) analysis of stainless steel.
A whole-system approach to x-ray spectroscopy in cargo inspection systems
NASA Astrophysics Data System (ADS)
Langeveld, Willem G. J.; Gozani, Tsahi; Ryge, Peter; Sinha, Shrabani; Shaw, Tim; Strellis, Dan
The bremsstrahlung x-ray spectrum used in high-energy, high-intensity x-ray cargo inspection systems is attenuated and modified by the materials in the cargo in a Z-dependent way. Therefore, spectroscopy of the detected x rays yields information about the Z of the x-rayed cargo material. It has previously been shown that such ZSpectroscopy (Z-SPEC) is possible under certain circumstances. A statistical approach, Z-SCAN (Z-determination by Statistical Count-rate ANalysis), has also been shown to be effective, and it can be used either by itself or in conjunction with Z-SPEC when the x-ray count rate is too high for individual x-ray spectroscopy. Both techniques require fast x-ray detectors and fast digitization electronics. It is desirable (and possible) to combine all techniques, including x-ray imaging of the cargo, in a single detector array, to reduce costs, weight, and overall complexity. In this paper, we take a whole-system approach to x-ray spectroscopy in x-ray cargo inspection systems, and show how the various parts interact with one another. Faster detectors and read-out electronics are beneficial for both techniques. A higher duty-factor x-ray source allows lower instantaneous count rates at the same overall x-ray intensity, improving the range of applicability of Z-SPEC in particular. Using an intensity-modulated advanced x-ray source (IMAXS) allows reducing the x-ray count rate for cargoes with higher transmission, and a stacked-detector approach may help material discrimination for the lowest attenuations. Image processing and segmentation allow derivation of results for entire objects, and subtraction of backgrounds. We discuss R&D performed under a number of different programs, showing progress made in each of the interacting subsystems. We discuss results of studies into faster scintillation detectors, including ZnO, BaF2 and PbWO4, as well as suitable photo-detectors, read-out and digitization electronics. We discuss high-duty-factor linear-accelerator x-ray sources and their associated requirements, and how such sources improve spectroscopic techniques. We further discuss how image processing techniques help in correcting for backgrounds and overlapping materials. In sum, we present an integrated picture of how to optimize a cargo inspection system for x-ray spectroscopy.
G³del, Manuel
More than two years of observation with Chandra and XMM-Newton has provided a rich harvest of new results on the physics of stellar coronae and winds. High-resolution X-ray spectroscopy in particular has opened new windows to the structure, the dynamics and the composition of stellar atmospheres. The present paper presents selected results from the areas of hot and cool stars and star formation, summarizing new views of the thermal structure and energy release in stellar coronae, observations of magnetically active brown dwarfs, the structure of winds in hot stars, the physics in colliding-wind binary systems, and X-rays from protostars and stellar jets. PMID:12804238
Wuest, Craig R. (Danville, CA); Bionta, Richard M. (Livermore, CA); Ables, Elden (Livermore, CA)
An x-ray detector which provides for the conversion of x-ray photons into photoelectrons and subsequent amplification of these photoelectrons through the generation of electron avalanches in a thin gas-filled region subject to a high electric potential. The detector comprises a cathode (photocathode) and an anode separated by the thin, gas-filled region. The cathode may comprise a substrate, such a beryllium, coated with a layer of high atomic number material, such as gold, while the anode can be a single conducting plane of material, such as gold, or a plane of resistive material, such as chromium/silicon monoxide, or multiple areas of conductive or resistive material, mounted on a substrate composed of glass, plastic or ceramic. The charge collected from each electron avalanche by the anode is passed through processing electronics to a point of use, such as an oscilloscope.
Wuest, C.R.; Bionta, R.M.; Ables, E.
An x-ray detector is disclosed which provides for the conversion of x-ray photons into photoelectrons and subsequent amplification of these photoelectrons through the generation of electron avalanches in a thin gas-filled region subject to a high electric potential. The detector comprises a cathode (photocathode) and an anode separated by the thin, gas-filled region. The cathode may comprise a substrate, such a beryllium, coated with a layer of high atomic number material, such as gold, while the anode can be a single conducting plane of material, such as gold, or a plane of resistive material, such as chromium/silicon monoxide, or multiple areas of conductive or resistive material, mounted on a substrate composed of glass, plastic or ceramic. The charge collected from each electron avalanche by the anode is passed through processing electronics to a point of use, such as an oscilloscope. 3 figures.
Spectral analysis of X-ray binaries
Fridriksson, Joel Karl
In this thesis, I present work from three separate research projects associated with observations of X-ray binaries. Two of those revolve around spectral characteristics of neutron star low-mass X-ray binaries (NS-LMXBs), ...
An introduction and overview of the Advanced Photon Source at Argonne National Laboratory, the technology that produces the brightest X-ray beams in the Western Hemisphere, and the research carried out by scientists using those X-rays.
Mathematical techniques and subsequent computer software were developed to process energy-dispersive x-ray fluorescence spectra for elemental analysis of airborne particulate matter collected on filters. The research concerned two areas: (1) determination of characteristic x-ray ...
Experimental spectral measurements of heavy K-edge filtered beams for x-ray computed mammotomography
NASA Astrophysics Data System (ADS)
Crotty, Dominic J.; McKinley, Randolph L.; Tornai, Martin P.
A compact, dual modality computed mammotomography (CmT) and single photon emission computed tomography (SPECT) system for dedicated 3D breast imaging is in development. The CmT component utilizes novel, heavy K-edge filtration to practicably narrow the energy spectrum of the cone-shaped x-ray beam incident on the patient's pendant, uncompressed breast. This quasi-monochromatic beam in CmT is expected to improve discrimination of tissue with very similar attenuation coefficients while restraining dose levels to below that of existing dual view mammography. Our previous extensive simulation studies showed the optimal energy range that provides maximum dose efficiency for a 50/50 adipose/glandular breast is in the 35-40keV range. This current study aims to experimentally validate previous simulation results. Here, experimental pre-breast and post-breast collimated x-ray beam spectral measurements are made under tube operating voltages between 40-100kVp using filter materials from Z=13-74, with K-edge values spanning that of Ce (K=40.4keV), and using different attenuating thicknesses of filter material, approximately equivalent to the 200 th and 500 th attenuating value layer (VL) thickness. Ce-filtered post breast spectra for 8cm to 18cm breasts are measured for a range of breast adipose/glandular compositions. Evaluated figures of merit include mean beam energy, spectral full-width at tenth-maximum, beam hardening and dose for the range of breast sizes. Measurements are shown to corroborate the simulations, and both indicate that for a given dose a 200 th VL of Ce filtration may have the most optimal performance in the dedicated mammotomography paradigm.
NASA Technical Reports Server (NTRS)
Morrison, Dennis R. (Inventor); Mosier, Benjamin (Inventor)
Microcapsules prepared by encapsulating an aqueous solution of a protein, drug or other bioactive substance inside a semi-permeable membrane by are disclosed. The microcapsules are formed by interfacial coacervation under conditions where the shear forces are limited to 0-100 dynes per square centimeter at the interface. By placing the microcapsules in a high osmotic dewatering solution. the protein solution is gradually made saturated and then supersaturated. and the controlled nucleation and crystallization of the protein is achieved. The crystal-filled microcapsules prepared by this method can be conveniently harvested and stored while keeping the encapsulated crystals in essentially pristine condition due to the rugged. protective membrane. Because the membrane components themselves are x-ray transparent, large crystal-containing microcapsules can be individually selected, mounted in x-ray capillary tubes and subjected to high energy x-ray diffraction studies to determine the 3-D smucture of the protein molecules. Certain embodiments of the microcapsules of the invention have composite polymeric outer membranes which are somewhat elastic, water insoluble, permeable only to water, salts, and low molecular weight molecules and are structurally stable in fluid shear forces typically encountered in the human vascular system.
NASA Astrophysics Data System (ADS)
Spaeth, J. M.; Hangleiter, Th; Koschnick, F. K.; Pawlik, Th
In X-ray storage phosphors an image is formed and stored by generation of room temperature stable radiation-induced electron and hole trap centres. The image is read-out by recording a photo-stimulated luminescence (PSL) from a doped activator, generally stimulating the electron trap centres. The best-known and hitherto most efficient X-ray storage phosphor is BaFBr:EuZ+. However, the exact mechanism of its functioning is not yet understood. The present discussion of the storage and read-out mechanisms is critically reviewed. New results about the role of oxygen Contamination of BaFBr:Eu2+ are presented: if there is much less oxygen present than Edc, then the PSL efficiency decreases and the stimulation energy increases. A new efficient X-ray storage phosphor is presented: Cs2NaYF6 doped with trivalent rare earth activators. Its properties are described and preliminary results on X-radiation-induced radiation damage centres in undoped Cs2NaYF6 are presented.
Henderson, D J; Good, D E; Hogge, K W; Molina, I; Howe, R A; Lutz, S S; Flores, P A; McGillivray, K D; Skarda, W M; Nelson, D S; Ormond, E S
A rod pinch x-ray diode assembly culminates in a coaxial anode cathode arrangement where a small anode rod extends through the aperture of a cathode plate. Shotto- shot repeatability in rod placement, and thus x-ray source spot position, has potential to positively affect radiographic image quality. Thus, how to both control and measure, according to a Cartesian coordinate system, anode rod tip displacement (x, y) (off the beam line-of-sight retical) and also anode rod tip extension (z) (along the line-of-sight center line) become salient issues relative to radiographic image set utility. To address these issues both hardware fabrication and x-ray diode assembly methods were reviewed, and additional controls were introduced. A photogrammetric procedure was developed to quantify anode rod tip position in situ. Computer models and mock-up assemblies with precision fiducials were produced to validate this procedure. Therefore, both anode rod tip displacement and anode rod tip extension parameters were successfully controlled. Rod position was measured and met the required specifications: (1) radial displacement <0.25 mm and (2) axial placement of ▒0.25 mm. We demonstrated that precision control and measurement of large scale components is achievable in a pulse power system (i.e., hardware and operations). Correlations with diode performance and radiography are presented.
Baker, Kevin Louis
X-ray phase sensitive wave-front sensor techniques are detailed that are capable of measuring the entire two-dimensional x-ray electric field, both the amplitude and phase, with a single measurement. These Hartmann sensing and 2-D Shear interferometry wave-front sensors do not require a temporally coherent source and are therefore compatible with x-ray tubes and also with laser-produced or x-pinch x-ray sources.
Bioabsorbable bone fixation plates for X-ray imaging diagnosis by a radiopaque layer of barium sulfate and poly(lactic-co-glycolic acid).
Choi, Sung Yoon; Hur, Woojune; Kim, Byeung Kyu; Shasteen, Catherine; Kim, Myung Hun; Choi, La Mee; Lee, Seung Ho; Park, Chun Gwon; Park, Min; Min, Hye Sook; Kim, Sukwha; Choi, Tae Hyun; Choy, Young Bin
Bone fixation systems made of biodegradable polymers are radiolucent, making post-operative diagnosis with X-ray imaging a challenge. In this study, to allow X-ray visibility, we separately prepared a radiopaque layer and attached it to a bioabsorbable bone plate approved for clinical use (Inion, Finland). We employed barium sulfate as a radiopaque material due to the high X-ray attenuation coefficient of barium (2.196 cm(2) /g). The radiopaque layer was composed of a fine powder of barium sulfate bound to a biodegradable material, poly(lactic-co-glycolic acid) (PLGA), to allow layer degradation similar to the original Inion bone plate. In this study, we varied the mass ratio of barium sulfate and PLGA in the layer between 3:1 w/w and 10:1 w/w to modulate the degree and longevity of X-ray visibility. All radiopaque plates herein were visible via X-ray, both in vitro and in vivo, for up to 40 days. For all layer types, the radio-opacity decreased with time due to the swelling and degradation of PLGA, and the change in the layer shape was more apparent for layers with a higher PLGA content. The radiopaque plates released, at most, 0.5 mg of barium sulfate every 2 days in a simulated in vitro environment, which did not appear to affect the cytotoxicity. The radiopaque plates also exhibited good biocompatibility, similar to that of the Inion plate. Therefore, we concluded that the barium sulfate-based, biodegradable plate prepared in this work has the potential to be used as a fixation device with both X-ray visibility and biocompatibility. ® 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 103B:596-607, 2015. PMID:24964903
a Laboratory-Based X-Ray Phase Contrast Imaging Scanner with Applications in Biomedical and Non-Medical Disciplines
NASA Astrophysics Data System (ADS)
Hagen, C. K.; Diemoz, P. C.; Endrizzi, M.; Munro, P. R. T.; Szafraniec, M. B.; Millard, T. P.; Speller, R.; Olivo, D. A.
X-ray phase contrast imaging (XPCi) provides a much higher visibility of low-absorbing details than conventional, attenuation-based radiography. This is due to the fact that image contrast is determined by the unit decrement of the real part of the complex refractive index of an object rather than by its imaginary part (the absorption coefficient), which can be up to 1000 times larger for energies in the X-ray regime. This finds applications in many areas, including medicine, biology, material testing, and homeland security. Until lately, XPCi has been restricted to synchrotron facilities due to its demanding coherence requirements on the radiation source. However, edge illumination XPCi, first developed by one of the authors at the ELETTRA Synchrotron in Italy, substantially relaxes these requirements and therefore provides options to overcome this problem. Our group has built a prototype scanner that adapts the edge-illumination concept to standard laboratory conditions and extends it to large fields of view. This is based on X-ray sources and detectors available off the shelf, and its use has led to impressive results in mammography, cartilage imaging, testing of composite materials and security inspection. This article presents the method and the scanner prototype, and reviews its applications in selected biomedical and non-medical disciplines.
X-Ray Absorption Spectroscopy of Metallobiomolecules
Scott, Robert A.
9/6/09 1 X-Ray Absorption Spectroscopy of Metallobiomolecules The Outskirts of Structural Biology 6, 09] This is a tutorial about the use of X-ray Absorption Spectroscopy (XAS) in biology, RG; Eisenberger, P; Kincaid, BM "X-ray Absorption Spectroscopy of Biological Molecules" Annu. Rev
X-Ray Absorption Spectroscopy of Metallobiomolecules
Scott, Robert A.
2/9/07 1 X-Ray Absorption Spectroscopy of Metallobiomolecules The Outskirts of Structural Biology 9, 07] This is a tutorial about the use of X-ray Absorption Spectroscopy (XAS) in biology, RG; Eisenberger, P; Kincaid, BM "X-ray Absorption Spectroscopy of Biological Molecules" Annu. Rev
Chest X-Ray (Chest Radiography)
... x-rays. top of page What does the equipment look like? View larger with caption The equipment typically used for chest x-rays consists of ... tube is positioned about six feet away. The equipment may also be arranged with the x-ray ...
X-raying clumped stellar winds
L. M. Oskinova; W. -R. Hamann; A. Feldmeier
X-ray spectroscopy is a sensitive probe of stellar winds. X-rays originate from optically thin shock-heated plasma deep inside the wind and propagate outwards throughout absorbing cool material. Recent analyses of the line ratios from He-like ions in the X-ray spectra of O-stars highlighted problems with this general paradigm: the measured line ratios of highest ions are consistent with the location of the hottest X-ray emitting plasma very close to the base of the wind, perhaps indicating the presence of a corona, while measurements from lower ions conform with the wind-embedded shock model. Generally, to correctly model the emerging X-ray spectra, a detailed knowledge of the cool wind opacities based on stellar atmosphere models is prerequisite. A nearly grey stellar wind opacity for the X-rays is deduced from the analyses of high-resolution X-ray spectra. This indicates that the stellar winds are strongly clumped. Furthermore, the nearly symmetric shape of X-ray emission line profiles can be explained if the wind clumps are radially compressed. In massive binaries the orbital variations of X-ray emission allow to probe the opacity of the stellar wind; results support the picture of strong wind clumping. In high-mass X-ray binaries, the stochastic X-ray variability and the extend of the stellar-wind part photoionized by X-rays provide further strong evidence that stellar winds consist of dense clumps.
Not Available
This report briefly reviews the following topics: soft-x-ray imaging; reflective optics for hard x-rays; coherent XUV sources; spectroscopy with x-rays; detectors for coronary artery imaging; synchrotron-radiation optics; and support for the advanced light source.
Student X-Ray Fluorescence Experiments
ERIC Educational Resources Information Center
Fetzer, Homer D.; And Others
Describes the experimental arrangement for x-ray analysis of samples which involves the following: the radioisotopic x-ray disk source; a student-built fluorescence chamber; the energy dispersive x-ray detector, linear amplifier and bias supply; and a multichannel pulse height analyzer. (GS)
Are X-Rays Safe during Pregnancy?
... And most of these deformities are minor, like skin tags or an extra finger or toe. Could I have another test instead of an X-ray? You might be able to have an ultrasound exam instead of an X-ray. Ultrasound, which is also called sonography, is the best alternative to an X-ray. ...
Cryotomography x-ray microscopy state
Le Gros, Mark (Berkeley, CA); Larabell, Carolyn A. (Berkeley, CA)
An x-ray microscope stage enables alignment of a sample about a rotation axis to enable three dimensional tomographic imaging of the sample using an x-ray microscope. A heat exchanger assembly provides cooled gas to a sample during x-ray microscopic imaging.
X-ray Spectroscopy of Cool Stars
M. Guedel
High-resolution X-ray spectroscopy has addressed not only various topics in coronal physics of stars, but has also uncovered important features relevant for our understanding of stellar evolution and the stellar environment. I summarize recent progress in coronal X-ray spectroscopy and in particular also discuss new results from studies of X-rays from pre-main sequence stars.
X-ray diodes for laser fusion plasma diagnostics
Day, R.H.; Lee, P.; Saloman, E.B.; Nagel, D.J.
Photodiodes with x-ray sensitive photocathodes are commonly used as broadband x-ray detectors in fusion plasma diagnostics. We have measured the risetime of the detector system and have measured the quantum efficiency between 1 to 500 A of numerous photocathode materials of practical interest. The materials studied include aluminum, copper, nickel, gold, three forms of carbon, chromium, and cesium iodide. The results of the measurements are compared with Henke's semiempirical model of photoyield. We have studied the effects of long-term cathode aging and use as a plasma diagnostic on cathode quantum efficiency. In addition, we have measured the x-ray mass-absorption coefficient of several ultrasoft x-ray windows in energy regions where data were unavailable. Windows studied were made of aluminum, Formvar, polypropylene, and Kimfoil. Measurements between 1 to 50 A were performed with the Los Alamos Scientific Laboratory's low-energy x-ray calibration facility, and the measurements between 50 to 550 A were performed at the National Bureau of Standard's synchrotron ultraviolet radiation facility.
An upgraded x-ray spectroscopy diagnostic on MST
Clayton, D. J.; Almagri, A. F.; Burke, D. R.; Forest, C. B.; Goetz, J. A.; Kaufman, M. C.; O'Connell, R. [Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)
An upgraded x-ray spectroscopy diagnostic is used to measure the distribution of fast electrons in MST and to determine Z{sub eff} and the particle diffusion coefficient D{sub r}. A radial array of 12 CdZnTe hard-x-ray detectors measures 10-150 keV Bremsstrahlung from fast electrons, a signature of reduced stochasticity and improved confinement in the plasma. A new Si soft-x-ray detector measures 2-10 keV Bremsstrahlung from thermal and fast electrons. The shaped output pulses from both detector types are digitized and the resulting waveforms are fit with Gaussians to resolve pileup and provide good time and energy resolution. Lead apertures prevent detector saturation and provide a well-known etendue, while lead shielding prevents pickup from stray x-rays. New Be vacuum windows transmit >2 keV x-rays, and additional Al and Be filters are sometimes used to reduce low energy flux for better resolution at higher energies. Measured spectra are compared to those predicted by the Fokker-Planck code CQL3D to deduce Z{sub eff} and D{sub r}.
Calibration-free quantification of interior properties of porous media with x-ray computed tomography.
Hussein, Esam M A; Agbogun, H M D; Al, Tom A
A method is presented for interpreting the values of x-ray attenuation coefficients reconstructed in computed tomography of porous media, while overcoming the ambiguity caused by the multichromatic nature of x-rays, dilution by void, and material heterogeneity. The method enables determination of porosity without relying on calibration or image segmentation or thresholding to discriminate pores from solid material. It distinguishes between solution-accessible and inaccessible pores, and provides the spatial and frequency distributions of solid-matrix material in a heterogeneous medium. This is accomplished by matching an image of a sample saturated with a contrast solution with that saturated with a transparent solution. Voxels occupied with solid-material and inaccessible pores are identified by the fact that they maintain the same location and image attributes in both images, with voxels containing inaccessible pores appearing empty in both images. Fully porous and accessible voxels exhibit the maximum contrast, while the rest are porous voxels containing mixtures of pore solutions and solid. This matching process is performed with an image registration computer code, and image processing software that requires only simple subtraction and multiplication (scaling) processes. The process is demonstrated in dolomite (non-uniform void distribution, homogeneous solid matrix) and sandstone (nearly uniform void distribution, heterogeneous solid matrix) samples, and its overall performance is shown to compare favorably with a method based on calibration and thresholding. PMID:25576734
3D investigation of inclusions in diamonds using X-ray micro-tomography
NASA Astrophysics Data System (ADS)
Parisatto, M.; Nestola, F.; Artioli, G.; Nimis, P.; Harris, J. W.; Kopylova, M.; Pearson, G. D.
The study of mineral inclusions in diamonds is providing invaluable insights into the geochemistry, geodynamics and geophysics of the Earth's mantle. Over the last two decades, the identification of different inclusion assemblages allowed to recognize diamonds deriving from the deep upper mantle, the transition zone and even the lower mantle. In such research field the in-situ investigation of inclusions using non-destructive techniques is often essential but still remains a challenging task. In particular, conventional 2D imaging techniques (e.g. SEM) are limited to the investigation of surfaces and the lack of access to the third dimension represents a major limitation when trying to extract quantitative information. Another critical aspect is related to sample preparation (cutting, polishing) which is typically very invasive. Nowadays, X-ray computed micro-tomography (X-?CT) allows to overcome such limitations, enabling the internal microstructure of totally undisturbed samples to be visualized in a three-dimensional (3D) manner at the sub-micrometric scale. The final output of a micro-tomography experiment is a greyvalue 3D map of the variations of the X-ray attenuation coefficient (Ą) within the studied object. The high X-ray absorption contrast between diamond (almost transparent to X-rays) and the typical inclusion-forming minerals (olivines, garnets, pyroxenes, oxides and sulphides) makes X-?CT a straightforward method for the 3D visualization of inclusions and for the study of their spatial relationships with the diamond host. In this work we applied microfocus X-?CT to investigate silicate inclusions still trapped in diamonds, in order to obtain in-situ information on their exact position, crystal size, shape and X-ray absorption coefficient (which is related to their composition). We selected diamond samples from different deposits containing mainly olivine and garnet inclusions. The investigated samples derived from the Udachnaya pipe (Siberia, Russia), the Jericho Kimberlite (Slave Craton, Canada) and SŃo Luiz-Juina (Brazil). The information obtained by tomographic experiments were combined with X-ray single-crystal diffraction data (see Nestola et al 2011) in order to identify the inclusion parageneses (peridotitic, eclogitic or websteritic) and to finally determine the origin of the studied diamonds. Our results showed that, by combining X-?CT with X-ray diffraction data, it is possible to exactly determine the 3D position of each inclusion together with their crystal size, even though they cannot be detected by using an optical microscope. In addition, such method could have strong crystallographic implications for inclusions still trapped in diamonds as it enables the application of a reliable numerical absorption correction to the 3D intensity data collections. REF. Nestola, F., Nimis, P., Ziberna, L., Longo, M., Marzoli, A., Harris, J.W., Manghnani, M.H., Fedortchouk, Y. (2011): First crystal-structure determination of olivine in diamond: composition and implications for provenance in the Earth's mantle. Earth Planet. Sci. Lett., 305, 249-255.
X-ray spectroscopy of low-mass X-ray binaries
Juett, Adrienne Marie, 1976-
I present high-resolution X-ray grating spectroscopy of neutron stars in low-mass X-ray binaries (LMXBs) using instruments onboard the Chandra X-ray Observatory and the X-ray Multi-Mirror Mission (XMM-Newton). The first ...
An accuracy assessment of photo-ionization cross-section datasets for 1-2 keV x-rays in light elements using PIXE
NASA Astrophysics Data System (ADS)
Heirwegh, C. M.; Pradler, I.; Campbell, J. L.
Proton-induced x-ray emission (PIXE) was used to assess the accuracy of the National Institute of Standards and Technology XCOM and FFAST photo-ionization cross-section databases in the low energy region (1-2 keV) for light elements. Characteristic x-ray yields generated in thick samples of Mg, Al and Si in elemental and oxide form, were compared to fundamental parameters computations of the expected x-ray yields; the database for this computation included XCOM attenuation coefficients. The resultant PIXE instrumental efficiency constant was found to differ by 4-6% between each element and its oxide. This discrepancy was traced to use of the XCOM Hartree-Slater photo-electric cross-sections. Substitution of the FFAST Hartree-Slater cross-sections reduced the effect. This suggests that for 1-2 keV x-rays in light element absorbers, the FFAST predictions of the photo-electric cross-sections are more accurate than the XCOM values.
Establishment of ANSI N13.11 X-ray radiation fields for personal dosimetry performance test by computation and experiment.
Kim, J L; Kim, B H; Chang, S Y; Lee, J K
This paper describes establishment by computational and experimental methods of the American National Standard Institute (ANSI) N13.11 X-ray radiation fields by the Korea Atomic Energy Research Institute (KAERI). These fields were used in the standard irradiations of various personal dosimeters for the personal dosimetry performance test program performed by the Ministry of Science and Technology of Korea in the autumn of 1995. Theoretical X-ray spectra produced from two KAERI X-ray generators were estimated using a modified Kramers' theory with target attenuation and backscatter correction and their spectral distributions experimentally measured by a high-purity germanium semiconductor detector through proper corrections for measured pulse height distributions with photopeak efficiency, Compton fraction, and K-escape fraction. The average energies and conversion coefficients obtained from the computation and experimental methods, when compared with ANSI N13.11 and the recently published National Institute of Standards and Technology X-ray beams, appeared to be in good agreement--(+/-)3% between corresponding values--and thus, could be satisfactorily applied in the performance test of personal dosimeters. PMID:9467054
Gamma Ray Attenuation Coefficient Measurement in Energies 1172 keV and 1332 keV for Neutron Absorbent Saturated Solutions
Jalali; Majid
The compounds, NaBO, HBO, CdCl and NaCl and their solutions, attenuate gamma rays in addition to neutron absorption. These compounds are widely used in shielding of neutron sources, reactor control and neutron converters. Mass attenuation coefficients of gamma related to saturated solutions of the above four compounds, in energies 1172 keV and 1332 keV have been measured by NaI detector
Determination of photon attenuation coefficient, porosity and field capacity of soil by gamma-ray transmission for 60, 356 and 662 keV gamma rays
D. Demir; A. ▄n; M. ųzg³l; Y. ?ahin
Gamma-ray transmission methods have been used accurately for the study of the properties of soil in the agricultural purposes. In this study, photon attenuation coefficient, porosity and field capacity of soil are determined by using gamma-ray transmission method. To this end, the soil sample was collected from Erzurum and a 2ū2 in NaI (Tl) scintillation detector measured the attenuation of
Measurements of an optimized beam for x-ray computed mammotomography
NASA Astrophysics Data System (ADS)
McKinley, Randolph L.; Samei, Ehsan; Brzymialkiewicz, Caryl N.; Tornai, Martin P.; Floyd, Carey E., Jr.
Simulation results from previous studies indicate that a quasi-monochromatic x-ray beam can be produced using a newly developed beam filtration technique. This technique utilizes heavy filtration with novel high Z filter materials having k-edges just above those of CsI, producing a near monochromatic beam with mean energy optimized for detection. The value of a near monochromatic x-ray source for a fully 3D tomography application is the expected improved ability to separate tissues with very small differences in attenuation coefficients for a range of uncompressed breast sizes while maintaining dose levels at or below existing dual view mammography. In this study, we experimentally investigate a set of filter materials (Al, Cu, Ag, Ce, W, and Pb), filter thicknesses (10th, 100th, and 200th VL), and tube potentials (40-80 kVp) using a newly constructed test apparatus. Initial experimental results corroborate simulations and indicate that this approach can improve image quality (SNR) at constant dose. Al, Cu, W, and Pb provide optimal exposure efficiency results at 60 kVp and above. Decreasing relative improvements are observed above 100th VL filter thickness at 78 cm SID. Results are obtained without significant tube heating (except at 40 kVp). In addition, simulations indicate significant reductions in beam hardening. This optimized beam will be incorporated into a novel cone-beam x-ray computed mammotomography sub-system together with an emission tomograph in a dual modality CT/SPECT application specific emission and transmission tomography system for fully 3D uncompressed breast imaging.
Bone mineral densitometry with x-ray and radionuclide sources: a theoretical comparison.
Chakraborty, D P; Barnes, G T
Two methods of dual-photon absorptiometry (DPA) utilizing an x-ray tube instead of a radionuclide source have recently been introduced. In one method kVp switching is employed and two transmitted intensities at each pixel are determined. In the other method, K-edge filtration combined with a single kVp spectrum is used, but photons in two energy windows are counted. We present a theoretical analysis of the two methods, focusing on a figure of merit which is essentially the exposure efficiency (the precision for a given entrance exposure) and tube loading. We also compare their exposure efficiencies to theoretical limits that no DPA system can exceed. Our study indicates that the K-edge-filtered method is more exposure efficient by about a factor of 2. The switched-kVp method requires less heat units per scan by about a factor of 3. A hybrid K-edge switched-kVp method is suggested which achieves the same exposure efficiency as the K-edge-filtered method at lesser tube loading. Our theoretical model is based on published x-ray spectra and attenuation coefficients and is in good agreement with other simulation work. It is of interest that a point source of Gd-153 would be even more exposure efficient, achieving about 90% of the theoretical limit. However, in practice, the Gd source is of finite size and limited strength, and consequently the radionuclide method cannot achieve as good a precision as either x-ray method in similar scan times. PMID:1961163
Steinmeyer, Peter A. (Farmington, NM)
A radiation filter for filtering radiation beams of wavelengths within a preselected range of wavelengths comprises a radiation transmissive substrate and an attenuating layer deposited on the substrate. The attenuating layer may be deposited by a sputtering process or a vacuum process. Beryllium may be used as the radiation transmissive substrate. In addition, a second radiation filter comprises an attenuating layer interposed between a pair of radiation transmissive layers.
Steinmeyer, P.A.
A radiation filter for filtering radiation beams of wavelengths within a preselected range of wavelengths comprises a radiation transmissive substrate and an attenuating layer deposited on the substrate. The attenuating layer may be deposited by a sputtering process or a vacuum process. Beryllium may be used as the radiation transmissive substrate. In addition, a second radiation filter comprises an attenuating layer interposed between a pair of radiation transmissive layers. 4 figs.
Near optimal energy selective x-ray imaging system performance with simple detectors
Alvarez, Robert E. [Aprend Technology, Mountain View, California 94043 (United States)
Purpose: This article describes a method to achieve near optimal performance with low energy resolution detectors. Tapiovaara and Wagner [Phys. Med. Biol. 30, 519-529 (1985)] showed that an energy selective x-ray system using a broad spectrum source can produce images with a larger signal to noise ratio (SNR) than conventional systems using energy integrating or photon counting detectors. They showed that there is an upper limit to the SNR and that it can be achieved by measuring full spectrum information and then using an optimal energy dependent weighting. Methods: A performance measure is derived by applying statistical detection theory to an abstract vector space of the line integrals of the basis set coefficients of the two function approximation to the x-ray attenuation coefficient. The approach produces optimal results that utilize all the available energy dependent data. The method can be used with any energy selective detector and is applied not only to detectors using pulse height analysis (PHA) but also to a detector that simultaneously measures the total photon number and integrated energy, as discussed by Roessl et al. [Med. Phys. 34, 959-966 (2007)]. A generalization of this detector that improves the performance is introduced. A method is described to compute images with the optimal SNR using projections in a ''whitened'' vector space transformed so the noise is uncorrelated and has unit variance in both coordinates. Material canceled images with optimal SNR can also be computed by projections in this space. Results: The performance measure is validated by showing that it provides the Tapiovaara-Wagner optimal results for a detector with full energy information and also a conventional detector. The performance with different types of detectors is compared to the ideal SNR as a function of x-ray tube voltage and subject thickness. A detector that combines two bin PHA with a simultaneous measurement of integrated photon energy provides near ideal performance across a wide range of operating conditions. Conclusions: Low energy resolution detectors can be used in energy selective x-ray imaging systems to produce images with near optimal performance.
X-ray tube-based diffraction enhanced imaging prototype images of full-thickness breast specimens: reader study evaluation
L. S. Faulconer; C. Parham; D. J. Connor; M. Koomen; C. Kuzmiak; D. Pavic; C. A. Livasy; E. Kim; D. Zeng; E. B. Cole; Z. Zhong; E. D. Pisano
Conventional mammographic image contrast is derived from x-ray absorption, resulting in breast structure visualization due to density gradients that attenuate radiation without distinction between transmitted and scattered or refracted x-rays. This leads to image blurring and contrast reduction, hindering the early detection of small or otherwise occult cancers. Diffraction enhanced imaging (DEI) allows for dramatically increased contrast with decreased radiation
X-ray lithography using holographic images
Howells, Malcolm R. (Berkeley, CA); Jacobsen, Chris (Sound Beach, NY)
A non-contact X-ray projection lithography method for producing a desired X-ray image on a selected surface of an X-ray-sensitive material, such as photoresist material on a wafer, the desired X-ray image having image minimum linewidths as small as 0.063 .mu.m, or even smaller. A hologram and its position are determined that will produce the desired image on the selected surface when the hologram is irradiated with X-rays from a suitably monochromatic X-ray source of a selected wavelength .lambda.. On-axis X-ray transmission through, or off-axis X-ray reflection from, a hologram may be used here, with very different requirements for monochromaticity, flux and brightness of the X-ray source. For reasonable penetration of photoresist materials by X-rays produced by the X-ray source, the wavelength X, is preferably chosen to be no more than 13.5 nm in one embodiment and more preferably is chosen in the range 1-5 nm in the other embodiment. A lower limit on linewidth is set by the linewidth of available microstructure writing devices, such as an electron beam.
NASA Technical Reports Server (NTRS)
Rossj, B.
The evolution of X-ray astronomy up to the launching of the Einstein observatory is presented. The evaluation proceeded through the following major steps: (1) discovery of an extrasolar X-ray source, Sco X-1, orders of magnitude stronger than astronomers believed might exist; (2) identification of a strong X-ray source with the Crab Nebula; (3) identification of Sco X-1 with a faint, peculiar optical object; (4) demonstration that X-ray stars are binary systems, each consisting of a collapsed object accreting matter from an ordinary star; (5) discovery of X-ray bursts; (6) discovery of exceedingly strong X-ray emission from active galaxies, quasars and clusters of galaxies; (7) demonstration that the principal X-ray source is a hot gas filling the space between galaxies.
X ray imaging microscope for cancer research
NASA Technical Reports Server (NTRS)
Hoover, Richard B.; Shealy, David L.; Brinkley, B. R.; Baker, Phillip C.; Barbee, Troy W., Jr.; Walker, Arthur B. C., Jr.
The NASA technology employed during the Stanford MSFC LLNL Rocket X Ray Spectroheliograph flight established that doubly reflecting, normal incidence multilayer optics can be designed, fabricated, and used for high resolution x ray imaging of the Sun. Technology developed as part of the MSFC X Ray Microscope program, showed that high quality, high resolution multilayer x ray imaging microscopes are feasible. Using technology developed at Stanford University and at the DOE Lawrence Livermore National Laboratory (LLNL), Troy W. Barbee, Jr. has fabricated multilayer coatings with near theoretical reflectivities and perfect bandpass matching for a new rocket borne solar observatory, the Multi-Spectral Solar Telescope Array (MSSTA). Advanced Flow Polishing has provided multilayer mirror substrates with sub-angstrom (rms) smoothnesss for the astronomical x ray telescopes and x ray microscopes. The combination of these important technological advancements has paved the way for the development of a Water Window Imaging X Ray Microscope for cancer research.
Extended range X-ray telescope
NASA Technical Reports Server (NTRS)
Hoover, R. B. (inventor)
An X-ray telescope system is described which is comprised of a tubular mount having a collecting region remote from the one axial end. A soft X-ray/XUV subsystem associated with the collecting region directs only relatively soft, near on-axis X-rays/XUV radiation incident on a first portion of the collecting region into a first detector sensitive to relatively soft X-rays/XUV radiation. A hard X-ray subsystem associated with the collecting region directs only relatively hard near on-axis X-rays incident on a second portion of the collecting region into a second detector sensitive to relatively hard X-rays.
High resolution spectroscopy of X-ray emission from high mass X-ray binaries
F. Nagase; S. Watanabe
This article briefly reviews first the progress of spectroscopy in X-ray astronomy from proportional counters, a major instrument in early phase of X-ray astronomy, to gas scintillation proportional counters, X-ray CCD cameras, transmission and reflection gratings, and finally to X-ray micro-calorimeters. As a typical example of spectral features observed from high mass X-ray binaries (HMXBs), the spectra observed from Vela
Functional relations between total scattering and backscattering for retrieving the profile of the attenuation coefficient in the atmosphere from lidar-sensing data
Kovalev, V.A. (A.I. Voeikov Main Geophysical Observatory, St. Petersburg (Russian Federation))
The possibility of using a variable along a sensing path backscattering phase function in lidar data processing with the goal of increasing the accuracy of retrieving the profile of the attenuation coefficient in the inhomogeneous atmosphere is analyzed. Approximated dependences of the total aerosol scattering an aerosol backscattering are given based on the published experimental data. By way of example, the model profiles of the attenuation coefficient are given retrieved with the use of the scattering phase functions being constant and variable along the sensing path. 12 refs., 5 figs.
Three dimensional imaging of porosity and tracer concentration distributions in a dolostone sample during diffusion experiments using X-ray micro-CT
NASA Astrophysics Data System (ADS)
Agbogun, H. M. D.; Al, Tom A.; Hussein, Esam M. A.
X-ray micro-computed tomography (micro-CT) techniques for measuring the three-dimensional (3-D) distributions of diffusion-accessible porosity (?d) and temporal tracer-concentrations (C(t)) within a dolostone sample subjected to solute diffusion are developed and tested in this work. The ?d and C(t) measurements are based on spatially resolved changes in X-ray attenuation coefficients in sequentially acquired 3-D micro-CT datasets using two (calibration and relative) analytical approaches. The measured changes in X-ray attenuation coefficient values are a function of the mass of X-ray absorbing potassium-iodide tracer present in voxels. Mean ?d values of 3.8% and 6.5% were obtained with the calibration and the relative approaches, respectively. The detection limits for ?d measurements at individual voxel locations are 20% and 36% with the calibration and the relative methods, respectively. The detection limit for C(t) are 0.12 M and 0.22 M with the calibration and the relative approaches, respectively. Results from the calibration method are affected by a beam-hardening artifact and although results from the relative approach are not affected by the artifact, they are subject to high detection limits. This work presents a quantitative assessment of micro-CT data for studies of solute transport. Despite limitations in precision and accuracy, the method provides quantitative 3-D distributions of ?d and C(t) that reflect solute diffusion in heterogeneous porous geologic media.
Three dimensional imaging of porosity and tracer concentration distributions in a dolostone sample during diffusion experiments using X-ray micro-CT.
Agbogun, H M D; Al, Tom A; Hussein, Esam M A
X-ray micro-computed tomography (micro-CT) techniques for measuring the three-dimensional (3-D) distributions of diffusion-accessible porosity (?(d)) and temporal tracer-concentrations (C(t)) within a dolostone sample subjected to solute diffusion are developed and tested in this work. The ?(d) and C(t) measurements are based on spatially resolved changes in X-ray attenuation coefficients in sequentially acquired 3-D micro-CT datasets using two (calibration and relative) analytical approaches. The measured changes in X-ray attenuation coefficient values are a function of the mass of X-ray absorbing potassium-iodide tracer present in voxels. Mean ?(d) values of 3.8% and 6.5% were obtained with the calibration and the relative approaches, respectively. The detection limits for ?(d) measurements at individual voxel locations are 20% and 36% with the calibration and the relative methods, respectively. The detection limit for C(t) are 0.12 M and 0.22 M with the calibration and the relative approaches, respectively. Results from the calibration method are affected by a beam-hardening artifact and although results from the relative approach are not affected by the artifact, they are subject to high detection limits. This work presents a quantitative assessment of micro-CT data for studies of solute transport. Despite limitations in precision and accuracy, the method provides quantitative 3-D distributions of ?(d) and C(t) that reflect solute diffusion in heterogeneous porous geologic media. PMID:23298531
NSDL National Science Digital Library
This University of Washington Web site "is intended to serve both as an introductory tutorial to anomalous scattering and as a general tool for designing experiments based on anomalous scattering." Visitors can find a periodic table and a chart supplying X-ray absorption edge data. Students needing assistance with the concept of anomalous scattering will find the tutorial explaining the interactions of incident photons having relatively high and low energy with scattering electrons very instructive. The site also supplies users with information about Friedel's Law and MAD experiments.
Three-dimensional characterization of electrodeposited lithium microstructures using synchrotron X-ray phase contrast imaging.
Eastwood, David S; Bayley, Paul M; Chang, Hee Jung; Taiwo, Oluwadamilola O; Vila-Comamala, Joan; Brett, Daniel J L; Rau, Christoph; Withers, Philip J; Shearing, Paul R; Grey, Clare P; Lee, Peter D
The electrodeposition of metallic lithium is a major cause of failure in lithium batteries. The 3D microstructure of electrodeposited lithium 'moss' in liquid electrolytes has been characterised at sub-micron resolution for the first time. Using synchrotron X-ray phase contrast imaging we distinguish mossy metallic lithium microstructures from high surface area lithium salt formations by their contrasting X-ray attenuation. PMID:24898258
Computerized X-ray tomography analysis of sandbox models: Examples of thin-skinned thrust systems
Bernard Colletta; Jean Letouzey; Roberto Pinedo; Jean Franńois Ballard; Pascal Balķ
Computerized X-ray tomography applied to analog sandbox experiments performed in a normal gravity field makes possible the analysis of the kinematic evolution, as well as the three-dimensional geometry, of models that simulate tectonic deformations. Most of the plastic or viscous analog materials generally used in a normal gravity field for such models have X-ray attenuations compatible with medical scanner images.
Method for beam hardening correction in quantitative computed X-ray tomography
NASA Technical Reports Server (NTRS)
Yan, Chye Hwang (Inventor); Whalen, Robert T. (Inventor); Napel, Sandy (Inventor)
Each voxel is assumed to contain exactly two distinct materials, with the volume fraction of each material being iteratively calculated. According to the method, the spectrum of the X-ray beam must be known, and the attenuation spectra of the materials in the object must be known, and be monotonically decreasing with increasing X-ray photon energy. Then, a volume fraction is estimated for the voxel, and the spectrum is iteratively calculated.
Paganin, D; Gureyev, T E; Mayo, S C; Stevenson, A W; Nesterets, Ya I; Wilkins, S W
The science of wave-field phase retrieval and phase measurement is sufficiently mature to permit the routine reconstruction, over a given plane, of the complex wave-function associated with certain coherent forward-propagating scalar wave-fields. This reconstruction gives total knowledge of the information that has been encoded in the complex wave-field by passage through a sample of interest. Such total knowledge is powerful, because it permits the emulation in software of the subsequent action of an infinite variety of coherent imaging systems. Such 'virtual optics', in which software forms a natural extension of the 'hardware optics' in an imaging system, may be useful in contexts such as quantitative atom and X-ray imaging, in which optical elements such as beam-splitters and lenses can be realized in software rather than optical hardware. Here, we develop the requisite theory to describe such hybrid virtual-physical imaging systems, which we term 'omni optics' because of their infinite flexibility. We then give an experimental demonstration of these ideas by showing that a lensless X-ray point projection microscope can, when equipped with the appropriate software, emulate an infinite variety of optical imaging systems including those which yield interferograms, Zernike phase contrast, Schlieren imaging and diffraction-enhanced imaging. PMID:15157198
Utilization of nanoparticles as X-ray contrast agents for diagnostic imaging applications.
De La Vega, Josķ Carlos; Hõfeli, Urs O
Among all the diagnostic imaging modalities, X-ray imaging techniques are the most commonly used owing to their high resolution and low cost. The improvement of these techniques relies heavily on the development of novel X-ray contrast agents, which are molecules that enhance the visibility of internal structures within the body in X-ray imaging. To date, clinically used X-ray contrast agents consist mainly of small iodinated molecules that might cause severe adverse effects (e.g.?allergies, cardiovascular diseases and nephrotoxicity) in some patients owing to the large and repeated doses that are required to achieve good contrast. For this reason, there is an increasing interest in the development of alternative X-ray contrast agents utilizing elements with high atomic numbers (e.g.?gold, bismuth, ytterbium and tantalum), which are well known for exhibiting high absorption of X-rays. Nanoparticles (NPs) made from these elements have been reported to have better imaging properties, longer blood circulation times and lower toxicity than conventional iodinated X-ray contrast agents. Additionally, the combination of two or more of these elements into a single carrier allows for the development of multimodal and hybrid contrast agents. Herein, the limitations of iodinated X-ray contrast agents are discussed and the parameters that influence the efficacy of X-ray contrast agents are summarized. Several examples of the design and production of both iodinated and iodine-free NP-based X-ray contrast agents are then provided, emphasizing the studies performed to evaluate their X-ray attenuation capabilities and their toxicity in vitro and in vivo. Copyright ® 2014 John Wiley & Sons, Ltd. PMID:25044541
NASA Astrophysics Data System (ADS)
Lewin, Walter; van der Klis, Michiel
1. Accreting neutron stars and black holes: a decade of discoveries D. Psaltis; 2. Rapid X-ray variability M. van der Klis; 3. New views of thermonuclear bursts T. Strohmayer and L. Bildsten; 4. Black hole binaries J. McClintock and R. Remillard; 5. Optical, ultraviolet and infrared observations of X-ray binaries P. Charles and M. Coe; 6. Fast X-ray transients and X-ray flashes J. Heise and J. in 't Zand; 7. Isolated neutron stars V. Kaspi, M. Roberts and A. Harding; 8. Globular cluster X-ray sources F. Verbunt and W. Lewin; 9. Jets from X-ray binaries R. Fender; 10. X-Rays from cataclysmic variables E. Kuulkers, A. Norton, A. Schwope and B. Warner; 11. Super soft sources P. Kahabka and E. van den Heuvel; 12. Compact stellar X-ray sources in normal galaxies G. Fabbiano and N. White; 13. Accretion in compact binaries A. King; 14. Soft gamma repeaters and anomalous X-ray pulsars: magnetar candidates P. Woods and C. Thompson; 15. Cosmic gamma-ray bursts, their afterglows, and their host galaxies K. Hurley, R. Sari and S. Djorgovski; 16. Formation and evolution of compact stellar X-ray sources T. Tauris and E. van den Heuvel.
NASA Astrophysics Data System (ADS)
Glover, T. E.; Hertlein, M. P.; Southworth, S. H.; Allison, T. K.; van Tilborg, J.; Kanter, E. P.; Krõssig, B.; Varma, H. R.; Rude, B.; Santra, R.; Belkacem, A.; Young, L.
Ultrafast X-ray science is an exciting frontier that promises the visualization of electronic, atomic and molecular dynamics on atomic time and length scales. A largely unexplored area of ultrafast X-ray science is the use of light to control how X-rays interact with matter. To extend control concepts established for long-wavelength probes to the X-ray regime, the optical control field must drive a coherent electronic response on a timescale comparable to femtosecond core-hole lifetimes. An intense field is required to achieve this rapid response. Here, an intense optical control pulse is observed to efficiently modulate photoelectric absorption for X-rays and to create an ultrafast transparency window. We demonstrate an application of X-ray transparency relevant to ultrafast X-ray sources: an all-photonic temporal cross-correlation measurement of a femtosecond X-ray pulse. The ability to control X-ray-matter interactions with light will create new opportunities for present and next-generation X-ray light sources.
Glover, Ernie; Hertlein, Marcus; Southworth, Steve; Allison, Tom; van Tilborg, Jeroen; Kanter, Elliot; Krassig, B.; Varma, H.; Rude, Bruce; Santra, Robin; Belkacem, Ali; Young, Linda
Ultrafast x-ray science is an exciting frontier that promises the visualization of electronic, atomic and molecular dynamics on atomic time and length scales. A largelyunexplored area of ultrafast x-ray science is the use of light to control how x-rays interact with matter. In order to extend control concepts established for long wavelengthprobes to the x-ray regime, the optical control field must drive a coherent electronic response on a timescale comparable to femtosecond core-hole lifetimes. An intense field is required to achieve this rapid response. Here an intense optical control pulse isobserved to efficiently modulate photoelectric absorption for x-rays and to create an ultrafast transparency window. We demonstrate an application of x-ray transparencyrelevant to ultrafast x-ray sources: an all-photonic temporal cross-correlation measurement of a femtosecond x-ray pulse. The ability to control x-ray/matterinteractions with light will create new opportunities at current and next-generation x-ray light sources.
Plasma-driven Z-pinch X-ray loading and momentum coupling in meteorite and planetary materials
NASA Astrophysics Data System (ADS)
Remo, John L.; Furnish, Michael D.; Lawrence, R. Jeffery; Lawrence
X-ray momentum coupling coefficients, C M, were determined by measuring stress waveforms in planetary materials subjected to impulsive radiation loading from the Sandia National Laboratories Z-machine. Velocity interferometry (VISAR) diagnostics provided equation-of-state data. Targets were iron and stone meteorites, magnesium-rich olivine (dunite) solid and powder (~5-300 ?m), and Si, Al, and Fe calibration targets. Samples were ~1-mm thick and, except for Si, backed by LiF single-crystal windows. X-ray spectra combined thermal radiation (blackbody 170-237 eV) and line emissions from pinch materials (Cu, Ni, Al, or stainless steel). Target fluences of 0.4-1.7 kJ/cm2 at intensities of 43-260GW/cm2 produced plasma pressures of 2.6-12.4 GPa. The short (~5 ns) drive pulses gave rise to attenuating stress waves in the samples. The attenuating wave impulse is constant, allowing accurate C M measurements from rear-surface motion. C M was 1.9 - 3.1 ū 10-5 s/m for stony meteorites, 2.7 and 0.5 ū 10-5 s/m for solid and powdered dunite, 0.8 - 1.4 ū 10-5 s/m for iron meteorites, and 0.3, 1.8, and 2.7 ū 10-5 s/m respectively for Si, Fe, and Al calibration targets. Results are consistent with geometric scaling from recent laser hohlraum measurements. CTH hydrocode modeling of X-ray coupling to porous silica corroborated experimental measurements and supported extrapolations to other materials. CTH-modeled C M for porous materials was low and consistent with experimental results. Analytic modeling (BBAY) of X-ray radiation-induced momentum coupling to selected materials was also performed, often producing higher C M values than experimental results. Reasons for the higher values include neglect of solid ejecta mechanisms, turbulent mixing of heterogeneous phases, variances in heats of melt/vaporization, sample inhomogeneities, wave interactions at the sample/window boundary, and finite sample/window sizes. The measurements validate application of C M to (inhomogeneous) planetary materials from high-intensity soft X-ray radiation.
Soft x-ray shock loading and momentum coupling in meteorite and planetary materials.
Lawrence, R. Jeffery; Remo, John L. (Harvard University, Cambridge, MA); Furnish, Michael David
X-ray momentum coupling coefficients, C{sub M}, were determined by measuring stress waveforms in planetary materials subjected to impulsive radiation loading from the Sandia National Laboratories Z-machine. Results from the velocity interferometry (VISAR) diagnostic provided limited equation-of-state data as well. Targets were iron and stone meteorites, magnesium rich olivine (dunite) solid and powder ({approx}5--300 {mu}m), and Si, Al, and Fe calibration targets. All samples were {approx}1 mm thick and, except for Si, backed by LiF single-crystal windows. The x-ray spectrum included a combination of thermal radiation (blackbody 170--237 eV) and line emissions from the pinch material (Cu, Ni, Al, or stainless steel). Target fluences 0.4--1.7 kJ/cm{sup 2} at intensities 43--260 GW/cm{sup 2} produced front surface plasma pressures 2.6--12.4 GPa. Stress waves driven into the samples were attenuating due to the short ({approx}5 ns) duration of the drive pulse. Attenuating wave impulse is constant allowing accurate C{sub M} measurements provided mechanical impedance mismatch between samples and the window are known. Impedance-corrected C{sub M} determined from rear-surface motion was 1.9--3.1 x 10{sup -5} s/m for stony meteorites, 2.7 and 0.5 x 10{sup -5} s/m for solid and powdered dunite, 0.8--1.4 x 10{sup -5}.
Internal-conversion process in superintense ultrashort x-ray pulses
Kis, Daniel; Kalman, Peter; Keszthelyi, Tamas; Szivos, Janos [Budapest University of Technology and Economics, Institute of Nuclear Technics, Department of Nuclear Energy, Muegyetem rkpt. 9, H-1111 Budapest (Hungary); Budapest University of Technology and Economics, Institute of Physics, Department of Theoretical Physics, Budafoki ut 8. F. I. I. 10, H-1521 Budapest (Hungary)
The electron-nucleus interaction in a super-intense few-cycle x-ray pulse is investigated. The super-intense few-cycle x-ray pulse-induced internal conversion (IC) process is discussed in detail. The x-ray laser-pulse induced IC coefficient is calculated, and in particular, it is derived in the case of a pulse of Gaussian shape and for a bound-free electron transition. The IC coefficient of the IC process induced by a super-intense few-cycle soft-x-ray laser pulse in the case of the {sup 99m}Tc isomer is determined numerically. The results obtained for the IC coefficient show significant carrier angular frequency, carrier-envelope phase, and pulse-length dependencies. The infinite pulse-length limit and experimental aspects are also discussed.
Retrieval of phytoplankton biomass from simultaneous inversion of reflectance, the diffuse attenuation coefficient, and Sun-induced fluorescence in coastal waters
Yannick Huot; Catherine A. Brown; John J. Cullen
A model has been developed to retrieve phytoplankton absorption, a proxy for phytoplankton biomass, from observations of reflectance (R) and the diffuse attenuation coefficient (K d) collected by moored radiometers in coastal waters, where high concentrations of chromophoric dissolved organic matter (CDOM) confound conventional ocean color algorithms. The inversion uses simultaneously two forward models: (1) a look-up table (LUT) that
Retrieval of phytoplankton biomass from simultaneous inversion of reflectance, the diffuse attenuation coefficient, and Sun-induced fluorescence in coastal waters
Yannick Huot; Catherine A. Brown; John J. Cullen
A model has been developed to retrieve phytoplankton absorption, a proxy for phytoplankton biomass, from observations of reflectance (R) and the diffuse attenuation coefficient (Kd) collected by moored radiometers in coastal waters, where high concentrations of chromophoric dissolved organic matter (CDOM) confound conventional ocean color algorithms. The inversion uses simultaneously two forward models: (1) a look-up table (LUT) that accounts
Seasonal variability in the vertical attenuation coefficient at 490 nm (K490) in waters around Puerto Rico and US Virgin Islands
William J. Hernandez; Fernando Gilbes
Satellite sensors provide a valuable tool in understanding the seasonal variability of ocean color properties. The vertical diffuse attenuation coefficient (Kd) was evaluated for the waters around Puerto Rico and the US Virgin Islands. The MODIS K490 of Band 3 Level82 daily images were processed with a resolution of 1 kilometer for the year 2008. The images were projected to
Study of variance and covariance terms in linear attenuation coefficient measurements of irregular samples through the two media method by gamma-ray transmission
Renato Yoichi Ribeiro Kuramoto; Carlos Roberto Appoloni
The two media method permits the application of Beer's law (Thesis (Master Degree), Universidade Estadual de Londrina, PR, Brazil, pp. 23) for the linear attenuation coefficient determination of irregular thickness samples by gamma-ray transmission. However, the use of this methodology introduces experimental complexity due to the great number of variables to be measured. As consequence of this complexity, the uncertainties
Modeling contamination migration on the Chandra X-Ray Observatory
NASA Technical Reports Server (NTRS)
O'Dell, Stephen L.; Swartz, Douglas A.; Anderson, Scot K.; Chen, Kenny C.; Giordano, Rino J.; Knollenberg, Perry J.; Morris, Peter A.; Plucinsky, Paul P.; Tice, Neil W.; Tran, Hien
During its first 5 years of operation, the cold (-60 C) optical blocking filter of the Advanced CCD Imaging Spectrometer (ACIS), on board the Chandra X-ray Observatory, has accumulated a contaminating layer that attenuates the low-energy x rays. To assist in assessing the likelihood of successfully baking off the contaminant, members of the Chandra Team developed contamination-migration simulation software. The simulation follows deposition onto and (temperature-dependent) vaporization from surfaces comprising a geometrical model of the Observatory. A separate thermal analysis, augmented by on-board temperature monitoring, provides temperatures for each surface of the same geometrical model. This paper describes the physical basis for the simulations, the methodologies, and the predicted migration of the contaminant for various bake-out scenarios and assumptions.
NASA Astrophysics Data System (ADS)
Hessenbruch, A.
1995 is the centenary of the discovery of X-rays by the German physicist Wilhelm C Rontgen. In the past hundred years, the new rays have developed from being unknown to finding application in many walks of life, not least in medicine. This is so much so that in common speech the word `x-ray` refers not to a form of radiation but to an X-ray photograph taken for the purposes of diagnosis (as in: `I had an X-ray done to see if my leg was broken`). X-rays are now used routinely, and they are used both for diagnosis and for therapy. This paper will give an outline of the use of X-rays in medicine throughout our present century.
Stimulated Electronic X-Ray Raman Scattering
NASA Astrophysics Data System (ADS)
Weninger, Clemens; Purvis, Michael; Ryan, Duncan; London, Richard A.; Bozek, John D.; Bostedt, Christoph; Graf, Alexander; Brown, Gregory; Rocca, Jorge J.; Rohringer, Nina
We demonstrate strong stimulated inelastic x-ray scattering by resonantly exciting a dense gas target of neon with femtosecond, high-intensity x-ray pulses from an x-ray free-electron laser (XFEL). A small number of lower energy XFEL seed photons drive an avalanche of stimulated resonant inelastic x-ray scattering processes that amplify the Raman scattering signal by several orders of magnitude until it reaches saturation. Despite the large overall spectral width, the internal spiky structure of the XFEL spectrum determines the energy resolution of the scattering process in a statistical sense. This is demonstrated by observing a stochastic line shift of the inelastically scattered x-ray radiation. In conjunction with statistical methods, XFELs can be used for stimulated resonant inelastic x-ray scattering, with spectral resolution smaller than the natural width of the core-excited, intermediate state.
Martin Elvis, X-ray & XUV Active Optics, Soleil, 14-15 Dec 2006 Active X-ray OpticsActive X-ray Optics
Elvis, Martin
1 Martin Elvis, X-ray & XUV Active Optics, Soleil, 14-15 Dec 2006 Active X-ray OpticsActive X-ray Optics For The Next High Resolution X-ray Observatory Martin Elvis Harvard-Smithsonian Center for Astrophysics Cambridge, Massachusetts, USA #12;2 Martin Elvis, X-ray & XUV Active Optics, Soleil, 14-15 Dec
Greiner, Jochen
Part I MICROQUASARS AND X-RAY NOVAE allbook.tex; 15/11/2000; 21:23; p.1 #12; 2 allbook.tex; 15/11/2000; 21:23; p.2 #12; Recent results on X-ray novae and microquasars at radio and infrared wavelengths and infrared wavelengths have provided a sig- ni#12;cant contribution to our knowledge of X-ray novae
A Plethora of X-ray Telescopes
NSDL National Science Digital Library
This explanation describes the observatories we are currently using to study X-rays from space. Chandra, named for Nobel prize winner Subrahmanyan Chandrasekhar, was launched from the space shuttle in 1999. Current X-ray observatories include The Rossi X-ray Timing Explorer (RXTE), named after astronomer Bruno Rossi, and The Advanced Satellite for Cosmology and Astrophysics (ASCA). The site also discusses what observatories we will use in the coming years to explore the structure and evolution of the Universe.
Switching X-Ray Tubes Remotely
NASA Technical Reports Server (NTRS)
Bulthuis, Ronald V.
Convenient switch and relay circuit reduces risk of accidents. Proposed switching circuit for x-ray inspection system enables operator to change electrical connections to x-ray tubes remotely. Operator simply flips switch on conveniently-located selector box to change x-ray heads. Indicator lights on selector box show whether 160 or 320-kV head connected. Relays in changeover box provides proper voltages and coolants. Chance of making wrong connections and damaging equipment eliminated.
NASA Astrophysics Data System (ADS)
Hudec, R.; Pina, L.; Marsikova, V.; Inneman, A.
We report on technical and astrophysical aspects of Lobster-Eye wide-field X-ray telescopes expected to monitor the sky with high sensitivity and angular resolution of order of 1 arcmin. They will contribute essentially to study of various astrophysical objects such as AGN, SNe, Gamma-ray bursts (GRBs), X-ray flashes (XRFs), galactic binary sources, stars, CVs, X-ray novae, various transient sources, etc.
X-ray transmissive debris shield
Spielman, Rick B. (Albuquerque, NM)
A composite window structure is described for transmitting x-ray radiation and for shielding radiation generated debris. In particular, separate layers of different x-ray transmissive materials are laminated together to form a high strength, x-ray transmissive debris shield which is particularly suited for use in high energy fluences. In one embodiment, the composite window comprises alternating layers of beryllium and a thermoset polymer.
X-ray line emission from Capella
NASA Astrophysics Data System (ADS)
Holt, S. S.; Boldt, E. A.; Serlemitsos, P. J.; White, N. E.; Becker, R. H.; Mushotzky, R. F.; Smith, B. W.
X-ray emission-line components from Mg, Si, S, and Fe are unambiguously detected from Capella with the solid-state spectrometer onboard the Einstein Observatory. The X-ray spectrum is inconsistent with an isothermal corona, and requires components between 6-million K and at least 24-million K for an adequate fit. An inhomogeneous corona in which the X-ray emitting plasma is confined to magnetically contained loops appears to be reconcilable with all of the experimental evidence.
Hudec, R. [Astronomical Institute, AS CR, 25165 Ondrejov (Czech Republic); Czech Technical University in Prague, Faculty of Electrical Engineering (Czech Republic); Pina, L. [Czech Technical Universiry in Prague, Faculty of Nuclear Science, Prague (Czech Republic); Rigaku Innovative Technologies Europe, Prague (Czech Republic); Marsikova, V.; Inneman, A. [Rigaku Innovative Technologies Europe, Prague (Czech Republic)
We report on technical and astrophysical aspects of Lobster-Eye wide-field X-ray telescopes expected to monitor the sky with high sensitivity and angular resolution of order of 1 arcmin. They will contribute essentially to study of various astrophysical objects such as AGN, SNe, Gamma-ray bursts (GRBs), X-ray flashes (XRFs), galactic binary sources, stars, CVs, X-ray novae, various transient sources, etc.
McPherson, Armon (Oswego, IL); Mills, Dennis M. (Naperville, IL)
A fast, economical, and compact x-ray beam chopper with a small mass and a small moment of inertia whose rotation can be synchronized and phase locked to an electronic signal from an x-ray source and be monitored by a light beam is disclosed. X-ray bursts shorter than 2.5 microseconds have been produced with a jitter time of less than 3 ns.
X-ray microlaminography with polycapillary optics
Dabrowski, K. M.; Dul, D. T.; Wrobel, A.; Korecki, P. [Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow (Poland)] [Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow (Poland)
We demonstrate layer-by-layer x-ray microimaging using polycapillary optics. The depth resolution is achieved without sample or source rotation and in a way similar to classical tomography or laminography. The method takes advantage from large angular apertures of polycapillary optics and from their specific microstructure, which is treated as a coded aperture. The imaging geometry is compatible with polychromatic x-ray sources and with scanning and confocal x-ray fluorescence setups.
Ogo, Y.
In a spot film device, a cassette assembly for a film cassette is mounted for reciprocating in a tunnel between an X-ray exposure position and a position in which the cassette is automatically unloaded or loaded with film. Field defining masks are also mounted for translating selectively with the carriage. The masks are formed of the synthetic materials having minimal X-ray absorption and high rigidity, without an aperture, to define a sharp X-ray field.
Byung Mook Weon; Jung Ho Je; Yeukuang Hwu
In the last decade X-ray imaging based on phase contrast greatly advanced thanks to the use of unmonochromatic synchrotron hard X-rays. The recent advances are going beyond microradiology and microtomography to reach nanometre scale. This paper reviews basic theory and selected applications to biomedical and materials sciences. The forthcoming improvements in phase contrast X-ray imaging will lead to even better
NASA Technical Reports Server (NTRS)
Skinner, Gerald K.
Diffractive X-ray telescopes, using zone plates, phase Fresnel lenses, or related optical elements have the potential to provide astronomers with true imaging capability with resolution many orders of magnitude better than available in any other waveband. Lenses that would be relatively easy to fabricate could have an angular resolution of the order of micro-arc-seconds or even better, that would allow, for example, imaging of the distorted spacetime in the immediate vicinity of the super-massive black holes in the center of active galaxies. What then is precluding their immediate adoption? Extremely long focal lengths, very limited bandwidth, and difficulty stabilizing the image are the main problems. The history, and status of the development of such lenses is reviewed here and the prospects for managing the challenges that they present are discussed.
MODIS-based retrieval of suspended sediment concentration and diffuse attenuation coefficient in Chinese estuarine and coastal waters
NASA Astrophysics Data System (ADS)
Sokoletsky, Leonid; Yang, Xianping; Shen, Fang
Radiative transfer modelling in atmosphere, water, and on the air-water surface was used to create an algorithm and computer code for satellite monitoring Chinese estuarine and coastal waters. The atmospheric part of the algorithm is based on the Reference Evaluation of Solar Transmittance (REST) model for calculation of optical properties of the atmosphere from the top of the atmosphere to the target; for modelling optical properties from target towards satellite's sensor, an optical reciprocity principle has been used. An algorithm uses estimates derived from three different sources: 1) the MODIS-based software; 2) radiative transfer equations, and 3) well-known empirical relationships between measured parameters and optical depths and transmittances for such atmospheric components as molecules, aerosols, ozone, nitrogen dioxide, precipitable water vapor and uniformly mixed gases. Using this model allowed us to derive a reliable relationship relating an important parameter, the diffuse-to-global solar incoming irradiance ratio, to the aerosol optical thickness, solar zenith angle and wavelength. The surface and underwater parts of the algorithm contained theoretical and semi-empirical relationships between inherent (such as absorption, scattering and backscattering coefficients) and apparent (remote-sensing reflectance and diffuse attenuation coefficient, Kd) optical properties, and suspended sediment concentration (SSC) measured in the Yangtze River Estuary and its adjacent coastal area. The first false colour maps of SSC and Kd demonstrated a well accordance with the multi-year field observations in the region, and suggest promise for use of this algorithm for the regular monitoring of Chinese and worldwide natural waters.
Not Available
The purpose of the soft x-ray interferometry workshop held at Lawrence Berkeley Laboratory was to discuss with the scientific community the proposed technical design of the soft x-ray Fourier-transform spectrometer being developed at the ALS. Different design strategies for the instrument`s components were discussed, as well as detection methods, signal processing issues, and how to meet the manufacturing tolerances that are necessary for the instrument to achieve the desired levels of performance. Workshop participants were encouraged to report on their experiences in the field of Fourier transform spectroscopy. The ALS is developing a Fourier transform spectrometer that is intended to operate up to 100 eV. The motivation is solely improved resolution and not the throughput (Jaquinot) or multiplex (Fellgett) advantage, neither of which apply for the sources and detectors used in this spectral range. The proposed implementation of this is via a Mach-Zehnder geometry that has been (1) distorted from a square to a rhombus to get grazing incidence of a suitable angle for 100 eV and (2) provided with a mirror-motion system to make the path difference between the interfering beams tunable. The experiment consists of measuring the emergent light intensity (I(x)) as a function of the path difference (x). The resolving power of the system is limited by the amount of path difference obtainable that is 1 cm (one million half-waves at 200{angstrom} wavelength) in the design thus allowing a resolving power of one million. The free spectral range of the system is limited by the closeness with which the function I(x) is sampled. It is proposed to illuminate a helium absorption cell with roughly 1%-band-width light from a monochromator thus allowing one hundred aliases without spectral overlap even for sampling of I(x) at one hundredth of the Nyquist frequency.
X-rays from the youngest stars
NASA Technical Reports Server (NTRS)
Feigelson, Eric D.
The X-ray properties of classical and weak-lined T Tauri stars are briefly reviewed, emphasizing recent results from the ROSAT satellite and prospects for ASCA. The interpretation of the high level of T Tauri X-rays as enhanced solar-type magnetic activity is discussed and criticized. The census of X-ray emitters is significantly increasing estimates of galactic star formation efficiency, and X-ray emission may be important for self-regulation of star formation. ASCA images will detect star formation regions out to several kiloparsecs and will study the magnetically heated plasma around T Tauri stars. However, images will often suffer from crowding effects.
Ultrashort X-ray pulse science
Chin, A.H. [Univ. of California, Berkeley, CA (US). Dept. of Physics]|[Lawrence Berkeley National Lab., CA (US). Materials Science Div.
A variety of phenomena involves atomic motion on the femtosecond time-scale. These phenomena have been studied using ultrashort optical pulses, which indirectly probe atomic positions through changes in optical properties. Because x-rays can more directly probe atomic positions, ultrashort x-ray pulses are better suited for the study of ultrafast structural dynamics. One approach towards generating ultrashort x-ray pulses is by 90{sup o} Thomson scattering between terawatt laser pulses and relativistic electrons. Using this technique, the author generated {approx} 300 fs, 30 keV (0.4 {angstrom}) x-ray pulses. These x-ray pulses are absolutely synchronized with ultrashort laser pulses, allowing femtosecond optical pump/x-ray probe experiments to be performed. Using the right-angle Thomson scattering x-ray source, the author performed time-resolved x-ray diffraction studies of laser-perturbated InSb. These experiments revealed a delayed onset of lattice expansion. This delay is due to the energy relaxation from a dense electron-hole plasma to the lattice. The dense electron-hole plasma first undergoes Auger recombination, which reduces the carrier concentration while maintaining energy content. Longitudinal-optic (LO) phonon emission then couples energy to the lattice. LO phonon decay into acoustic phonons, and acoustic phonon propagation then causes the growth of a thermally expanded layer. Source characterization is instrumental in utilizing ultrashort x-ray pulses in time-resolved x-ray spectroscopies. By measurement of the electron beam diameter at the generation point, the pulse duration of the Thomson scattered x-rays is determined. Analysis of the Thomson scattered x-ray beam properties also provides a novel means of electron bunch characterization. Although the pulse duration is inferred for the Thomson scattering x-ray source, direct measurement is required for other x-ray pulse sources. A method based on the laser-assisted photoelectric effect (LAPE) has been demonstrated as a means of measuring ultrashort x-ray pulse durations. LAPE may also serve as the basis for a gated x-ray detector.
NASA Technical Reports Server (NTRS)
Xu, Yueming; Sutherland, Peter; Mccray, Richard; Ross, Randy R.
Detailed calculations of the development of the X-ray spectrum of 1987A are presented using more realistic models for the supernova composition and density structure provided by Woosley. It is shown how the emergence of the X-ray spectrum depends on the parameters of the model and the nature of its central energy source. It is shown that the soft X-ray spectrum should be dominated by a 6.4 keV Fe K(alpha) emission line that could be observed by a sensitive X-ray telescope.
G. Fabbiano
Today's sensistive, high resolution Chandra X-ray observations allow the study of many populations of X-ray sources. The traditional astronomical tools of photometric diagrams and luminosity functions are now applied to these populations, and provide the means for classifying the X-ray sources and probing their evolution. While overall stellar mass drives the amount of X-ray binaries in old stellar population, the amount of sources in star-forming galaxies is related to the star formation rate. Shart-lived, luminous, high mass binaries (HNXBs) dominate these young populations.
NASA Astrophysics Data System (ADS)
Luna, G. J. M.; Sokoloski, J. L.; Mukai, K.; Nelson, T.
Until recently, symbiotic binary systems in which a white dwarf accretes from a red giant were thought to be mainly a soft X-ray population. Here we describe the detection with the X-ray Telescope (XRT) on the Swift satellite of nine white dwarf symbiotics that were not previously known to be X-ray sources and one that had previously been detected as a supersoft X-ray source. The nine new X-ray detections were the result of a survey of 41 symbiotic stars, and they increase the number of symbiotic stars known to be X-ray sources by approximately 30%. The Swift/XRT telescope detected all of the new X-ray sources at energies greater than 2 keV. Their X-ray spectra are consistent with thermal emission and fall naturally into three distinct groups. The first group contains those sources with a single, highly absorbed hard component that we identify as probably coming from an accretion-disk boundary layer. The second group is composed of those sources with a single, soft X-ray spectral component that probably originates in a region where low-velocity shocks produce X-ray emission, i.e., a colliding-wind region. The third group consists of those sources with both hard and soft X-ray spectral components. We also find that unlike in the optical, where rapid, stochastic brightness variations from the accretion disk typically are not seen, detectable UV flickering is a common property of symbiotic stars. Supporting our physical interpretation of the two X-ray spectral components, simultaneous Swift UV photometry shows that symbiotic stars with harder X-ray emission tend to have stronger UV flickering, which is usually associated with accretion through a disk. To place these new observations in the context of previous work on X-ray emission from symbiotic stars, we modified and extended the ?/?/? classification scheme for symbiotic-star X-ray spectra that was introduced by Muerset et al. based upon observations with the ROSAT satellite, to include a new ? classification for sources with hard X-ray emission from the innermost accretion region. Because we have identified the elusive accretion component in the emission from a sample of symbiotic stars, our results have implications for the understanding of wind-fed mass transfer in wide binaries, and the accretion rate in one class of candidate progenitors of type Ia supernovae. Tables 1 and 3 are available in electronic form at http://www.aanda.org
The Lunar X-ray Observatory (LXO)
NASA Technical Reports Server (NTRS)
Porter, F. Scott
X-ray emission from charge exchange recombination between the highly ionized solar wind and neutral material i n Earth's magnetosheath has complicated x-ray observations of celestial objects with x-ray observatories including ROSAT, Chandra, XMM-Newton, and Suzaku. However, the charge-exchange emission can also be used as an important diagnostic of the solar-wind interacting with the magnetosheath. Soft x-ray observations from low-earth orbit or even the highly eccentric orbits of Chandra and XMM-Newton are likely superpositions of the celestial object of interest, the true extra-solar soft x-ray background, geospheric charge exchange, and heliospheric charge exchange. We show that with a small x-ray telescope placed either on the moon, in a similar vein as the Apollo ALSOP instruments, or at a stable orbit near L1, we can begin t o disentangle the complicated emission structure in the soft x-ray band. Here we present initial results of a feasibility study recently funded by NASA t o place a small x-ray telescope on the lunar surface. The telescope operates during lunar night to observe charge exchange interactions between the solar wind and magnetospheric neutrals, between the solar wind and the lunar atmosphere, and an unobstructed view of the soft x-ray background without the geospheric component.
An Imaging X-Ray Polarimetry Mission
NASA Astrophysics Data System (ADS)
Weisskopf, Martin C.; Bellazzini, R.; Costa, E.; Ramsey, B.; O'Dell, S.; Tennant, A.; Elsner, R.; Pavlov, G.; Matt, G.; Kaspi, V.; Coppi, P.; Wu, K.; Siegmund, O.
Technical progress both in x-ray optics and in polarization-sensitive x-ray detectors, which our groups have pioneered, enables a scientifically powerful --- yet inexpensive --- dedicated mission for imaging x-ray polarimetry. Such a mission is sufficiently sensitive to measure x-ray (linear) polarization for a broad range of cosmic sources --- particularly those involving neutron stars, stellar black holes, and supermassive black holes (active galactic nuclei). We describe the technical elements, discuss a mission concept, and synopsize the important physical and astrophysical questions such a mission would address.
Colloid Coalescence with Focused X Rays
Weon, B. M.; Kim, J. T.; Je, J. H. [X-ray Imaging Center, Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang, 790-784 (Korea, Republic of); Yi, J. M. [Samsung Advanced Institute of Technology, Yongin, Gyeonggi, 446-712 (Korea, Republic of); Wang, S.; Lee, W.-K. [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States)
We show direct evidence that focused x rays enable us to merge polymer colloidal particles at room temperature. This phenomenon is ascribed to the photochemical scission of colloids with x rays, reducing the molecular weight, glass transition temperature, surface tension, and viscosity of colloids. The observation of the neck bridge growth with time shows that the x-ray-induced colloid coalescence is analogous to viscoelastic coalescence. This finding suggests a feasible protocol of photonic nanofabrication by sintering or welding of polymers, without thermal damage, using x-ray photonics.
X-ray Observations of "Recycled" Pulsars
NASA Astrophysics Data System (ADS)
Bogdanov, Slavko
The Chandra X-ray Observatory has been instrumental in establishing the X-ray properties of the Galactic population of rotation-powered ("recycled") millisecond pulsars. In this talk I will provide a summary of deep X-ray studies of globular cluster millisecond pulsars, as well as several nearby field millisecond pulsars. These include thermally-emitting recycled pulsars that may provide stringent constraints on the elusive neutron star equation of state, and so-called "redback" binary pulsars, which seem to sporadically revert to an X-ray binary-like state.
X-ray laser microscope apparatus
Suckewer, Szymon (Princeton, NJ); DiCicco, Darrell S. (Plainsboro, NJ); Hirschberg, Joseph G. (Coral Gables, FL); Meixler, Lewis D. (East Windsor, NJ); Sathre, Robert (Princeton, NJ); Skinner, Charles H. (Lawrenceville, NJ)
A microscope consisting of an x-ray contact microscope and an optical microscope. The optical, phase contrast, microscope is used to align a target with respect to a source of soft x-rays. The source of soft x-rays preferably comprises an x-ray laser but could comprise a synchrotron or other pulse source of x-rays. Transparent resist material is used to support the target. The optical microscope is located on the opposite side of the transparent resist material from the target and is employed to align the target with respect to the anticipated soft x-ray laser beam. After alignment with the use of the optical microscope, the target is exposed to the soft x-ray laser beam. The x-ray sensitive transparent resist material whose chemical bonds are altered by the x-ray beam passing through the target mater GOVERNMENT LICENSE RIGHTS This invention was made with government support under Contract No. De-FG02-86ER13609 awarded by the Department of Energy. The Government has certain rights in this invention.
X-ray variability in a complete sample of Soft X-ray selected AGN
D. Grupe; H. -C. Thomas; K. Beuermann
We present ROSAT All-Sky Survey and ROSAT pointed observations (PSPC and HRI) of a complete sample of 113 bright soft X-ray AGN selected from the ROSAT Bright Source Catalog. We compare these observations in order to search for extreme cases of flux and spectral X-ray variability - X-ray transient AGN. Three definite transients and one transient candidate are found. The other sources show amplitude variations typically by factors of 2-3 on timescales of years. We found that the variability strength on timescales of days is a function of the steepness of the X-ray spectrum: steeper X-ray objects show stronger variability than flat X-ray spectrum sources. We also present new HRI measurements of our extreme X-ray transients IC 3599 and WPVS007. We discuss possible models to explain the X-ray transience and the variabilities observed in the non-transient sources.
Wide field x-ray telescopes: Detecting x-ray transients/afterglows related to GRBs
Hudec, Rene [Astronomical Institute of Czech Academy of Science, Observatory Ondrejov, 251 65 Ondrejov (Czech Republic); Pina, Ladislav [Faculty of Nuclear Engineering, Czech Technical University, Prague (Czech Republic); Inneman, Adolf [Department of Precision Mechanics and Optics, Faculty of Mechanical Engineering, Czech Technical University, Prague (Czech Republic); Gorenstein, Paul [Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts (United States)
The recent discovery of X-ray afterglows of GRBs opens the possibility of analyses of GRBs by their X-ray detections. However, imaging X-ray telescopes in current use mostly have limited fields of view. Alternative X-ray optics geometries achieving very large fields of view have been theoretically suggested in the 70's but not constructed and used so far. We review the geometries and basic properties of the wide-field X-ray optical systems based on one- and two-dimensional lobster-eye geometry and suggest technologies for their development and construction. First results of the development of double replicated X-ray reflecting flats for use in one-dimensional X-ray optics of lobster-eye type are presented and discussed. The optimum strategy for locating GRBs upon their X-ray counterparts is also presented and discussed.
X-ray spectroscopy of neutron star low-mass X-ray binaries
Krauss, Miriam Ilana
In this thesis, I present work spanning a variety of topics relating to neutron star lowmass X-ray binaries (LMXBs) and utilize spectral information from X-ray observations to further our understanding of these sources. ...
Point x-ray source using graphite nanofibers and its application to x-ray radiography
Takahiro Matsumoto; Hidenori Mimura
A point x-ray emission was obtained from a diode configuration composed of a graphite-nanofiber cold cathode and a conical-shaped copper metal anode. When combined with a highly sensitive charge coupled device (CCD) camera with a scintillator, this x-ray source was then used to obtain x-ray transmission images of a tungsten mesh and an x-ray test chart. The spatial resolution of
X-ray Diffraction (XRD) 1.0 What is X-ray Diffraction
Moeck, Peter
X-ray Diffraction (XRD) ┬Ę 1.0 What is X-ray Diffraction ┬Ę 2.0 Basics of Crystallography ┬Ę 3.0 Production of X-rays ┬Ę 4.0 Applications of XRD ┬Ę 5.0 Instrumental Sources of Error ┬Ę 6.0 Conclusions #12 (Roentgenstrahlinterferenzen), commonly known as X-ray diffraction (XRD), and was direct evidence for the periodic atomic
Small x-ray telescope based on lobster eye x-ray optics and pixel detector
NASA Astrophysics Data System (ADS)
Tich², VladimĒr; Hrom?Ēk, Martin; Hudec, Renķ; Inneman, Adolf; Jakubek, Jan; MarÜĒk, Ji?Ē; PĒna, Ladislav; Semencovß, Veronika; Ŗvķda, Libor
Two experimental modules of small X-ray telescopes based on the Lobster eye X-ray optics are presented. These modules are regarded to use for x-ray astronomy applications in space. At this time, the optical tests of these modules have been performed. Results of these tests are presented.
X-RAY SPECTROMETRY X-Ray Spectrom. 2008; 37: 629634
leaf, stem and root samples were analysed in vivo by micro x-ray absorption spectroscopy (XAS) at the Ni┬ŁK edge. Both x-ray absorption near edge structure and extended x-ray absorption fine structure biologically important Ni-containing model compounds. The results revealed that the majority of leaf, stem
Voltage-Thickness-Gray imaging physical model in X-ray energy auto-modulation.
Chen, Ping; Han, Yan; Pan, Jinxiao
Energy auto-modulation is an important tool in X-ray imaging, as it can improve the quality and longevity of an x-ray imaging system. Because of the complex nature of imaged objects, X-ray energy auto-modulation may be difficult. If there is a physical model about imaging mechanism, one can forecast the best imaging parameters using a pre-scan that can be fed into this model. This paper offers a physical model, which is called the Voltage-Thickness-Gray (VTG) model. Based on equivalent single-energy, this paper uses the empirical formula of X-ray attenuation and X-ray photon intensity to build this VTG model. Then use linear regression to estimate the model's parameters, by multi-voltage imaging about the steel wedge block. At last, by the experiment of the steel step block, verify this model and forecast the imaging tube voltage. The result shows this model can better reflect X-ray attenuation imaging properties, and can be used to forecast the imaging voltage. Also the forecast precision can achieve 90% or so. PMID:25080118
Differential X-ray phase-contrast imaging with a grating interferometer using a laboratory X-ray micro-focus tube
NASA Astrophysics Data System (ADS)
Yoon, Kwon-Ha; Ryu, Jong Hyun; Jung, Chang Won; Ryu, Cheol Woo; Kim, Young Jo; Kwon, Young Man; Park, Miran; Cho, Seungryong; Chon, Kwon Su
X-ray phase-contrast imaging can provide images with much greater soft-tissue contrast than conventional absorption-based images. In this paper, we describe differential X-ray phase-contrast images of insect specimens that were obtained using a grating-based Talbot interferometer and a laboratory X-ray source with a spot size of a few tens of micrometers. We developed the interferometer on the basis of the wavelength, periods, and height of the gratings; the field of view depends on the size of the grating, considering the refractive index of the specimen. The phase-contrast images were acquired using phase-stepping methods. The phase contrast imaging provided a significantly enhanced soft-tissue contrast compared with the attenuation data. The contour of the sample was clearly visible because the refraction from the edges of the object was strong in the differential phase-contrast image. Our results demonstrate that a grating-based Talbot interferometer with a conventional X-ray tube may be attractive as an X-ray imaging system for generating phase images. X-ray phase imaging obviously has sufficient potential and is expected to soon be a great tool for medical diagnostics.
NASA Technical Reports Server (NTRS)
OBrien, Susan K.; Workman, Gary L.
The space environment in which the Space Station Freedom and other space platforms will orbit is truly a hostile environment. For example, the currently estimated integral fluence for electrons above 1 Mev at 2000 nautical miles is above 2 x 1O(exp 10) electrons/sq cm/day and the proton integral fluence is above 1 x 10(exp 9) protons/sq cm/day. At the 200 - 400 nautical miles, which is more representative of the altitude which will provide the environment for the Space Station, each of these fluences will be proportionally less; however, the data indicates that the radiation environment will obviously have an effect on structural materials exposed to the environment for long durations. The effects of this combined environment is the issue which needs to be understood for the long term exposure of structures in space. At the same time, there will be substantial potential for collisions between the space platforms and space debris. The current NASA catalogue contains over 4500 objects floating in space which are not considered payloads. This debris can have significant effects on collision with orbiting spacecraft. In order to better understand the effect of these hostile phenomena on spacecraft, several types of studies are being performed to simulate at some level the effect of the environment. In particular the study of debris clouds produced by hypervelocity impact on the various surfaces anticipated on the Space Station is very important at this point in time. The need to assess the threat of such debris clouds on space structures is an on-going activity. The Space Debris Impact facility in Building 4612 provides a test facility to monitor the types of damage produced with hypervelocity impact. These facilities are used to simulate space environmental effects from energetic particles. Flash radiography or x-ray imaging has traditionally provided such information and as such has been an important tool for recording damage in situ with the event. The proper operation of the system can provide much useful information with respect to parametric analysis of the hypervelocity experiment. The following report outlines the procedures developed to optimize the operation of the x-ray imaging system and its operational characteristics.
Erin Miller
The Pacific Northwest National Laboratory is developing a range of technologies to broaden the field of explosives detection. Phased contrast X-ray imaging, which uses silicon gratings to detect distortions in the X-ray wave front, may be applicable to mail or luggage scanning for explosives; it can also be used in detecting other contraband, small-parts inspection, or materials characterization.
Subpicosecond Coherent Manipulation of X-Rays
Adams, Bernhard W. [Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, IL 60439 (United States)
The Takagi-Taupin theory is synthesized with the eikonal theory in a unified space-time approach, based upon microscopic electromagnetism. It is designed specifically to address x-ray diffraction in crystal structures being modified within down to a few femtosconds. Possible applications in the subpicosecond coherent manipulation of x-rays are given.
X-ray spectroscopy of magnetic CVs
NASA Astrophysics Data System (ADS)
Matt, Giorgio
I discuss two topics in X-ray spectroscopy of magnetic CVs: reflection from the white dwarf surface, and opacity effects in the post shock plasma. I also briefly mention future observational perspectives, with particular emphasis on the Constellation X-ray mission.
Columbia University X-Ray Measurements
a CsI crystal converts x-ray photons to visible light. A coating on the back side of the crystal multiple spectra during each shot. The electron temperature is inferred from the x-ray energy. A hard x resonance zones are shown in addition to the locations of the probes and magnetic diagnostics. X
X-ray laser cavity experiments
N. M. Ceglio; D. P. Gaines; J. Trebes; A. M. Hawryluk; D. G. Stearns; G. L. Howe
Progress has been made toward the development of multipass, soft x-ray laser cavities operating in a spectral range around 200 A. Experimental results on the characterization of normal incidence multilayer mirrors, the survival of multilayer mirrors in the hostile x-ray laser environment, and the performance of double pass cavities at 206 A to 209 A are presented.
... and can't easily be brought to the radiology department, a portable X-ray machine can be brought to the bedside. Portable X-rays are sometimes used in emergency departments, intensive care units (ICUs), and operating rooms. The technician or radiologist will position your child (either lying ...
X-ray Analysis of Unknown Minerals
NSDL National Science Digital Library
Dexter Perkins
In this exercise, students use X-ray analysis to identify unknown minerals. They are given two samples to grind up and X-ray, using Jade to identify them. Once the minerals are identified, students make a spreadsheet and do a series of calculations.
X-ray source populations in galaxies
G. Fabbiano
Today's sensitive, high-resolution X-ray observations allow the study of populations of X-ray sources, in the luminosity range of Galactic X-ray binaries, in galaxies as distant as 20-30 Mpc. The traditional astronomical tools of photometric diagrams and luminosity functions are now applied to these populations, providing a direct probe of the evolved binary component of different stellar populations. The study of the X-ray populations of E and S0 galaxies has revamped the debate on the formation and evolution of low-mass X-ray binaries (LMXBs) and on the role of globular clusters in these processes. While overall stellar mass drives the amount of X-ray binaries in old stellar populations, the amount of sources in star forming galaxies is related to the star formation rate. Short-lived, luminous, high-mass binaries (HMXBs) dominate these young populations. The most luminous sources in these systems are the debated ULXs, which have been suggested to be ~100-1000 Msol black holes, but could alternatively include a number of binaries with stellar mass black holes. Very soft sources have also been discovered in many galaxies and their nature is currently being debated. Observations of the deep X-ray sky, and comparison with deep optical surveys, are providing the first evidence of the X-ray evolution of galaxies.
X-Ray Detection Visits the Classroom
ERIC Educational Resources Information Center
Peralta, Luis; Farinha, Ana; Pinto, Ana
Film has been used to detect x-rays since the early days of their discovery by Rontgen. Although nowadays superseded by other techniques, film still provides a cheap means of x-ray detection, making it attractive in high-school or undergraduate university courses. If some sort of quantitative result is required, the film's optical absorbance orģ
X-ray imaging: Status and trends
R. W. Ryon; H. E. Martz; J. M. Hernandez; J. J. Haskins; R. A. Day; J. M. Brase; B. Cross; D. Wherry
There is a veritable renaissance occurring in x-ray imaging. X-ray imaging by radiography has been a highly developed technology in medicine and industry for many years. However, high resolution imaging has not generally been practical because sources have been relatively dim and diffuse, optical elements have been nonexistent for most applications, and detectors have been slow and of low resolution.
NASA Technical Reports Server (NTRS)
Podgorski, W. A.; Flanagan, Kathy A.; Freeman, Mark D.; Goddard, R. G.; Kellogg, Edwin M.; Norton, T. J.; Ouellette, J. P.; Roy, A. G.; Schwartz, Daniel A.
The alignment and X-ray imaging performance of the Advanced X-ray Astrophysics Facility (AXAF) Verification Engineering Test Article-I (VETA-I) was measured by the VETA-I X-Ray Detection System (VXDS). The VXDS was based on the X-ray detection system utilized in the AXAF Technology Mirror Assembly (TMA) program, upgraded to meet the more stringent requirements of the VETA-I test program. The VXDS includes two types of X-ray detectors: (1) a High Resolution Imager (HRI) which provides X-ray imaging capabilities, and (2) sealed and flow proportional counters which, in conjunction with apertures of various types and precision translation stages, provide the most accurate measurement of VETA-I performance. Herein we give an overview of the VXDS hardware including X-ray detectors, translation stages, apertures, proportional counters and flow counter gas supply system and associated electronics. We also describe the installation of the VXDS into the Marshall Space Flight Center (MSFC) X-Ray Calibration Facility (XRCF). We discuss in detail the design and performance of those elements of the VXDS which have not been discussed elsewhere; translation systems, flow counter gas supply system, apertures and thermal monitoring system.
High-throughput baggage scanning employing x-ray diffraction for accurate explosives detection
NASA Astrophysics Data System (ADS)
Green, Michael C.; Partain, Larry D.
X-ray systems dominate the installed base of airport baggage scanning systems for explosives detection. The majority are conveyer systems with projection line scanners. These systems can achieve a high throughput but exhibit a high false positive rate and require significant operator involvement. Systems employing computed tomography (CT) are currently being installed at a rapid rate. These can provide good discrimination of levels of xray absorption coefficient and can largely circumvent superimposition effects. Nonetheless CT measures only x-ray absorption coefficient per voxel which does not provide a means of specific material identification resulting in many false positives, and it is relatively straightforward to configure explosive materials so that they are undetectable by CT systems. Diffraction-based x-ray systems present a solution to this problem. They detect and measure atomic layer spacings in crystalline and microcrystalline materials with high sensitivity. This provides a means of specific material identification. The majority of explosive compounds are well crystallized solids at room temperature. X-ray diffraction systems using both conventional wavelength-dispersive diffraction and fixed-angle, multi-wavelength diffraction for improved throughput are described. Large-area, flat-panel x-ray detector technology coupled with an extended x-ray source will permit a full 3D volumetric x-ray diffraction scan of a bag in a single pass, (patent pending).
Experimental spectral measurements of heavy K-edge filtered beams for x-ray computed mammotomography
NASA Astrophysics Data System (ADS)
Crotty, D. J.; McKinley, R. L.; Tornai, M. P.
A dual modality computed mammotomography (CmT) and single photon emission computed tomography (SPECT) system for dedicated 3D breast imaging is in development. Using heavy K-edge filtration, the CmT component narrows the energy spectrum of the cone-shaped x-ray beam incident on the patient's pendant, uncompressed breast. This quasi-monochromatic beam is expected to improve discrimination of tissue with similar attenuation coefficients while restraining absorbed dose to below that of dual view mammography. Previous simulation studies showed the optimal energy that maximizes dose efficiency for a 50/50% adipose/glandular breast is between 30 and 40 keV. This study experimentally validates these results using pre-breast and post-breast spectral measurements made under tungsten tube voltages between 40 and 100 kVp using filter materials with K-edge values ranging from 15 to 70 keV. Different filter material thicknesses are used, approximately equivalent to the 200th and 500th attenuating value layer (VL) thickness. Cerium (K = 40.4 keV) filtered post-breast spectra for 8-18 cm breasts are measured for a range of breast compositions. Figures of merit include mean beam energy, spectral full-width at tenth-maximum, beam hardening and dose for the range of breast sizes. Measurements corroborate simulation results, indicating that for a given dose, a 200th VL of cerium filtration may have optimal performance in the dedicated mammotomography paradigm.
Experimental spectral measurements of heavy K-edge filtered beams for x-ray computed mammotomography.
Crotty, D J; McKinley, R L; Tornai, M P
A dual modality computed mammotomography (CmT) and single photon emission computed tomography (SPECT) system for dedicated 3D breast imaging is in development. Using heavy K-edge filtration, the CmT component narrows the energy spectrum of the cone-shaped x-ray beam incident on the patient's pendant, uncompressed breast. This quasi-monochromatic beam is expected to improve discrimination of tissue with similar attenuation coefficients while restraining absorbed dose to below that of dual view mammography. Previous simulation studies showed the optimal energy that maximizes dose efficiency for a 50/50% adipose/glandular breast is between 30 and 40 keV. This study experimentally validates these results using pre-breast and post-breast spectral measurements made under tungsten tube voltages between 40 and 100 kVp using filter materials with K-edge values ranging from 15 to 70 keV. Different filter material thicknesses are used, approximately equivalent to the 200th and 500th attenuating value layer (VL) thickness. Cerium (K = 40.4 keV) filtered post-breast spectra for 8-18 cm breasts are measured for a range of breast compositions. Figures of merit include mean beam energy, spectral full-width at tenth-maximum, beam hardening and dose for the range of breast sizes. Measurements corroborate simulation results, indicating that for a given dose, a 200th VL of cerium filtration may have optimal performance in the dedicated mammotomography paradigm. PMID:17228108
Non-destructive determination of fat content in green hams using ultrasound and X-rays.
de Prados, M; Fulladosa, E; Gou, P; Mu±oz, I; Garcia-Perez, J V; Benedito, J
This work addresses the use of ultrasound (US) and medical dual energy X-ray absorptiometry methods to predict the fat content in green pork hams. Ultrasonic velocity (?) and X-ray absorption were measured in 78 green hams. An increase in the fat content involved an increase in ? and a decrease in the X-ray attenuation measured at 2░C. Models developed to predict the fat content from the ultrasonic velocity or X-ray parameters provided errors of 2.97% and 4.65%, respectively. The combination of both US and X-ray technologies did not improve prediction accuracy. These models allowed green hams to be classified into three levels of fatness, with 88.5% and 65.4% of the hams correctly classified when using models based on ultrasonic and X-ray parameters, respectively. Therefore, US and X-rays emerge as useful quality control technologies with which to estimate the fat content in green pork hams. PMID:25687033
Imaging of Poly(?-hydroxy-ester) Scaffolds with X-ray Phase-Contrast Microcomputed Tomography
Appel, Alyssa A.; Larson, Jeffery C.; Somo, Sami; Zhong, Zhong; Spicer, Patrick P.; Kasper, F. Kurtis; Garson, Alfred B.; Zysk, Adam M.; Mikos, Antonios G.; Anastasio, Mark A.
Porous scaffolds based on poly(?-hydroxy-esters) are under investigation in many tissue engineering applications. A biological response to these materials is driven, in part, by their three-dimensional (3D) structure. The ability to evaluate quantitatively the material structure in tissue-engineering applications is important for the continued development of these polymer-based approaches. X-ray imaging techniques based on phase contrast (PC) have shown a tremendous promise for a number of biomedical applications owing to their ability to provide a contrast based on alternative X-ray properties (refraction and scatter) in addition to X-ray absorption. In this research, poly(?-hydroxy-ester) scaffolds were synthesized and imaged by X-ray PC microcomputed tomography. The 3D images depicting the X-ray attenuation and phase-shifting properties were reconstructed from the measurement data. The scaffold structure could be imaged by X-ray PC in both cell culture conditions and within the tissue. The 3D images allowed for quantification of scaffold properties and automatic segmentation of scaffolds from the surrounding hard and soft tissues. These results provide evidence of the significant potential of techniques based on X-ray PC for imaging polymer scaffolds. PMID:22607529
Andrew J. Gosling; Reba M. Bandyopadhyay; Katherine M. Blundell
We report on a campaign to identify the counterparts to the population of X-ray sources discovered at the centre of our Galaxy by Wang et al.(2002) using Chandra. We have used deep, near infrared images obtained on VLT/ISAAC to identify candidate counterparts as astrometric matches to the X-ray positions. Follow up Ks-band spectroscopic observations of the candidate counterparts are used to search for accretions signatures in the spectrum, namely the Brackett-Gamma emission line (Bandyopadhyay et al.1997). From our small initial sample, it appears that only a small percentage, ~2-3% of the ~1000 X-ray sources are high mass X-ray binaries or wind accreting neutron stars, and that the vast majority will be shown to be canonical low mass X-ray binaries and cataclysmic variables.
X-ray lasing in diatomic molecules
NASA Astrophysics Data System (ADS)
Kimberg, Victor; Zhang, Song Bin; Rohringer, Nina
We predict high-gain x-ray lasing in diatomic molecules by ultrafast core ionization of the C K- and O K-edges in CO and the N K-edge in N2 with an x-ray free-electron laser source. To estimate the spectral and temporal output of this molecular x-ray laser, we solve generalized Maxwell-Bloch equations, keeping track of the electronic and nuclear degrees of freedom. Despite the broad fluorescence bandwidth, the amplified x-ray emission shows a narrow spectrum. By controlling the molecular alignment and thereby the alignment of the transition dipole moment polarization and emission energy control of the x-ray laser radiation is achievable.
X-ray lasing in diatomic molecules
NASA Astrophysics Data System (ADS)
Kimberg, Victor; Rohringer, Nina
We predict high-gain x-ray lasing in diatomic molecules by ultrafast core ionization of the C K- and O K-edges in CO and the N K-edge in N2 with an x-ray free-electron laser source. We solve generalized Maxwell-Bloch equations, keeping track of the electronic and nuclear degrees of freedom. By controlling the molecular alignment and thereby the alignment of the transition dipole moment polarization control of the emitted x-ray radiation is achievable. Despite the broad fluorescence bandwidth, the amplified x-ray emission shows a narrow spectrum. Preparing the initial vibrational quantum state, the x-ray emission frequency can be tuned within the fluorescence band.
Solar x ray astronomy rocket program
NASA Technical Reports Server (NTRS)
The dynamics were studied of the solar corona through the imaging of large scale coronal structures with AS&E High Resolution Soft X ray Imaging Solar Sounding Rocket Payload. The proposal for this program outlined a plan of research based on the construction of a high sensitivity X ray telescope from the optical and electronic components of the previous flight of this payload (36.038CS). Specifically, the X ray sensitive CCD camera was to be placed in the prime focus of the grazing incidence X ray mirror. The improved quantum efficiency of the CCD detector (over the film which had previously been used) allows quantitative measurements of temperature and emission measure in regions of low x ray emission such as helmet streamers beyond 1.2 solar radii or coronal holes. Furthermore, the improved sensitivity of the CCD allows short exposures of bright objects to study unexplored temporal regimes of active region loop evolution.
Globular Cluster X-ray Sources
Frank Verbunt; Walter H. G. Lewin
After a brief historical overview we discuss the luminous X-ray sources in globular clusters of our Galaxy. This is followed by an overview of the very luminous X-ray sources studied in globular clusters of 14 other galaxies, and a discussion of their formation and the relation to X-ray sources outside globular clusters. We describe the discovery and classification of low-luminosity X-ray sources, and end the review with some remarks on the formation and evolution of X-ray sources in globular clusters. Observational results are summarized in three tables. Comments are very welcome. Please send them to email@example.com and firstname.lastname@example.com.
NASA Astrophysics Data System (ADS)
Hird, J. R.; Camara, C. G.; Putterman, S. J.
A source of x-rays capable of exciting the characteristic emission lines of Mo and Ag is demonstrated. The device, which requires no external high voltage supply, uses the triboelectric effect to produce a charge imbalance when silicone and a metal-loaded epoxy are made to repeatedly contact each other in vacuum. This provides a source of 40 keV electrons which generate bremsstrahlung and characteristic x-rays at a rate of >105 per contact cycle. By increasing the repetition rate of the contact cycle the viability of a device that emits 108 x-ray photons per second is suggested, making triboelectricity an inexpensive source of x-rays. The form factors and simplicity of such devices open up interesting possibilities for x-ray imaging.
CMP Control of Multi-Layer Inter-Layer Dielectrics (ILD) using X-ray Reflectivity
Bryant, Ross E. [Rohm and Haas Electronic Materials, 3804 E. Watkins Street, Phoenix, AZ 85034 (United States); Current Affiliation: Particle Measuring Systems, 5475 Airport Blvd, Boulder, CO 80301 (United States); Porter, Hethel [Rohm and Haas Electronic Materials, 3804 E. Watkins Street, Phoenix, AZ 85034 (United States); Gallegos, Jesus; O'Dell, Jeremy; Agnihotri, Dileep [Jordan Valley Semiconductors, Inc., 8601 Cross Park Drive 200, Austin, TX 78754 (Jordan)
Thin sacrificial films are used as cap layer in the back-end semiconductor processing for protecting the bulk porous inter-layer low-k dielectric during the CMP process. The existing optical measurement techniques struggle to separate these thin films from the bulk low-k due to very similar optical coefficients. Glancing angle x-ray reflectivity is well suited for separation of thin sacrificial film and bulk dielectric film as x-ray reflectivity depends strongly on changes in electron densities for two materials. This paper discusses the x-ray reflectivity technique and its applications for measurement of low-k stack and sacrificial oxide post CMP.
NASA Technical Reports Server (NTRS)
An overview of the current status of the ROSAT X-Ray satellite project is given. Areas discussed include an overview of problem areas, systems and mechanical subsystems, the electrical subsystem, power supply, data processing and transmission, the wide field camera, ground support equipment and the production scheduling. It is shown that the project is proceeding according to schedule, including the hardware production and costs. However, it is stated that estimated additional costs will exceed the plan. The previous schedule for production of the flight model will no longer be met. A modified milestone plan has been worked out with Dornier Systems. The current working schedule calls for a launch data of December 21, 1987; however, this does not take into account a 4-week buffer prior to transporting the flight model to the launch site. As of the date of this report, milestone M5 has been met. Previous problems with the gold vapor deposition on the flight model mirror due to contamination have been eliminated.
NASA Technical Reports Server (NTRS)
Strong, Keith T.; Haisch, Bernhard M. (compiler); Lemen, James R. (compiler); Acton, L. W.; Bawa, H. S.; Claflin, E. S.; Freeland, S. L.; Slater, G. L.; Kemp, D. L.; Linford, G. A.
The range of observing and analysis programs accomplished with the X-Ray Polychromator (XRP) instruments during the decline of solar cycle 21 and the rise of the solar cycle 22 is summarized. Section 2 describes XRP operations and current status. This is meant as a guide on how the instrument is used to obtain data and what its capabilities are for potential users. The science section contains a series of representative abstracts from recently published papers on major XRP science topics. It is not meant to be a complete list but illustrates the type of science that can come from the analysis of the XRP data. There then follows a series of appendixes that summarize the major data bases that are available. Appendix A is a complete bibliography of papers and presentations produced using XRP data. Appendix B lists all the spectroscopic data accumulated by the Flat Crystal Spectrometer (FCS). Appendix C is a compilation of the XRP flare catalogue for events equivalent to a GOES C-level flare or greater. It lists the start, peak and end times as well as the peak Ca XIX flux.
NASA Technical Reports Server (NTRS)
Identifying stars that explode, right before they explode, is a tricky proposition since the end of starlife comes swiftly: in thermonuclear deflagrations, in nuclear exhaustion, or maybe in a rapid swirling merger of two dead stellar cores. On the right in the image above is an image of the galaxy NGC 1404 taken by the UV/optical Telescope (UVOT) on the Swift observatory. The circle surrounds SN 2007on, a supernova of Type Ia produced by the explosion of a white dwarf star in a binary system. These types of supernovae are important since they are believed to be 'standard candles', events which have the same intrinsic brightness which can serve as an important yardstick to measure cosmic distances. On the left is an image of the same galaxy taken by the Chandra X-ray observatory four years before the supernova. Conspicuous in the SN source circle is a bright source in the Chandra image, believed to be emission from a compact object+normal star companion: a similar system to the supposed precursor of SN 2007on. If true this would be the first time a Type Ia supernova precursor has ever been seen. But astronomers are still debating whether the Chandra source really is the precursor or not; it seems there's a slight but significant difference in the location of the Chandra source and the supernova. Stay tuned for more developments.
Kaonic mass by critical absorption of kaonic-atom x rays
Lum, G.K.; Wiegand, C.E.; Kessler, E.G. Jr.; Deslattes, R.D.; Jacobs, L.; Schwitz, W.; Seki, R.
The energy of x rays from the transition 6h..-->..5g in kaonic atoms of potassium falls on the K absorption edge of erbium. Measurement of the kaonic-x-ray attenuation in a precisely calibrated set of Er foils yields the x-ray energy 57 458.8 +- 6.3 eV. The kaon mass is related to energy through the Klein-Gordon equation plus corrections for radiative effects, electron screening, and other effects. The negative-kaon mass was found to be 493.640 +- 0.054 MeV/c/sup 2/ in agreement with the currently accepted value 493.669 +- 0.018 MeV/c/sup 2/ which was determined from x rays emitted by high-Z atoms where the corrections were larger than for Z = 19.
Multimodal hard X-ray imaging of a mammography phantom at a compact synchrotron light source
Schleede, Simone; Bech, Martin; Achterhold, Klaus; Potdevin, Guillaume; Gifford, Martin; Loewen, Rod; Limborg, Cecile; Ruth, Ronald; Pfeiffer, Franz
The Compact Light Source is a miniature synchrotron producing X-rays at the interaction point of a counter-propagating laser pulse and electron bunch through the process of inverse Compton scattering. The small transverse size of the luminous region yields a highly coherent beam with an angular divergence of a few milliradians. The intrinsic monochromaticity and coherence of the produced X-rays can be exploited in high-sensitivity differential phase-contrast imaging with a grating-based interferometer. Here, the first multimodal X-ray imaging experiments at the Compact Light Source at a clinically compatible X-ray energy of 21?keV are reported. Dose-compatible measurements of a mammography phantom clearly demonstrate an increase in contrast attainable through differential phase and dark-field imaging over conventional attenuation-based projections. PMID:22713884
Detection of x ray sources in PROS
NASA Technical Reports Server (NTRS)
Deponte, J.; Primini, F. A.
The problem of detecting discrete sources in x-ray images has much in common with the problem of automatic source detection at other wavelengths. In all cases, one searches for positive brightness enhancements exceeding a certain threshold, which appear consistent with what one expects for a point source, in the presence of a (possibly) spatially variable background. Multidimensional point spread functions (e.g., dependent on detector position and photon energy) are also common. At the same time, the problem in x-ray astronomy has some unique aspects. For example, for typical x-ray exposures in current or recent observatories, the number of available pixels far exceeds the number of actual x-ray events, so Poisson, rather than Gaussian statistics apply. Further, extended cosmic x-ray sources are common, and one often desires to detect point sources in the vicinity or even within bright, diffuse x-ray emission. Finally, support structures in x-ray detectors often cast sharp shadows in x-ray images making it necessary to detect sources in a region of rapidly varying exposure. We have developed a source detection package within the IRAF/PROS environment which attempts to deal with some of the problems of x-ray source detection. We have patterned our package after the successful Einstein Observatory x-ray source detection programs. However, we have attempted to improve the flexibility and accessibility of the functions and to provide a graphical front-end for the user. Our philosophy has been to use standard IRAF tasks whenever possible for image manipulation and to separate general functions from mission-specific ones. We will report on the current status of the package and discuss future developments, including simulation tasks, to allow the user to assess detection efficiency and source significance, tasks to determine source intensity, and alternative detection algorithms.
Quantitative Measurements of X-ray Intensity
Haugh, M. J., Schneider, M.
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.
Globular Cluster X-ray Sources
NASA Astrophysics Data System (ADS)
Pooley, David
Globular clusters and X-ray astronomy have a long and fruitful history. Uhuru and OSO-7 revealed a population of highly luminous (> 10^{36} erg/s) X-ray sources in globular clusters, and Einstein and ROSAT revealed a larger population of low luminosity (< 10^{33} erg/s) X-ray sources. It was realized early on that the high luminosity sources were low-mass X-ray binaries in outburst and that they were orders of magnitude more abundant per unit mass in globular clusters than in the rest of the Galaxy. However, the low luminosity sources proved difficult to classify. Many ideas were put forth -- including low-mass X-ray binaries in quiescence (qLMXBs), cataclysmic variables (CVs), active main-sequence binaries (ABs), and millisecond pulsars (MSPs) -- but secure identifications were scarce. In ROSAT observations of 55 globular clusters, about 25 low-luminosity X-ray sources were found. To date, Chandra has observed over 80 Galactic globular clusters, mainly with ACIS, and these observations have revealed over 1500 X-ray sources. The superb angular resolution has allowed for many counterpart identifications, providing clues to the nature of this population. It is a heterogenous mix of qLMXBs, CVs, ABs, and MSPs, and it has been shown that the qLMXBs and CVs are both, in part, overabundant like the luminous LMXBs. The number of X-ray sources in a globular cluster correlates very well with its encounter frequency. This points to dynamical formation scenarios for the X-ray sources and shows them to be excellent tracers of the complicated internal dynamics of globular clusters. The relation between the encounter frequency and the number of X-ray sources has been used to suggest that we have misunderstood the dynamical states of globular clusters.
X-ray emissions associated with thunderstorms
NASA Astrophysics Data System (ADS)
Mallick, S.; Rakov, V. A.; Dwyer, J. R.; Hill, J. D.
We used an x-ray detector, including a NaI scintillator and a photomultiplier tube, to (1) compare x-ray emissions during thunderstorm and non-thunderstorm days and (2) examine x-ray emissions associated with specific lightning processes. X-ray data were acquired in 2010 and 2011 at the Lightning Observatory in Gainesville (LOG) [e.g., Mallick et al., 2011] in conjunction with corresponding electric field and electric field derivative waveforms (for thunderstorm days). Record length was 240 ms. The system was triggered on the electric field during thunderstorms and manually on non-thunderstorm days. The average x-ray rate on thunderstorm days, 124 counts per second, is higher than that, 95 counts per second, on non-thunderstorm days, and the difference is statistically significant. Non-thunderstorm days were defined as those with no thunderstorms within at least 15 km of LOG. X-ray emissions on these days are attributed to cosmic rays and natural Earth radioactivity. Fig. 1 shows average x-ray counts per second in different energy ranges for both thunderstorm and non-thunderstorm days. On July 31st, 2011, we recorded x-ray bursts associated with three close multiple-stroke natural lightning flashes along with their electric field and electric field derivative waveforms. These flashes transported negative charge to ground. The total number of bursts is six, and they are all apparently associated with stepped and dart-stepped leaders. Interestingly, some subsequent-stroke leaders are more prolific x-ray producers than first-stroke leaders. Also, for the same leader, some steps are accompanied by pronounced x-ray signals, while others are not. Reference Mallick, S. et al., On Remote Measurements of Lightning Peak Currents, XIV International Conference on Atmospheric Electricity (ICAE), August 08-12, 2011, Rio de Janeiro, Brazil.
X-ray studies of near-frictionless carbon films.
Mehta, N. J.; Roy, S.; Johnson, J. A.; Woodford, J.; Zinovev, A.; Islam, Z.; Erdemir, A.; Sinha, S.; Fenske, G.; Prorok, B.; Energy Technology; Univ. of California; Auburn Univ.
Carbon-based coatings exhibit many attractive properties that make them good candidates for a wide range of engineering applications. Tribological studies of the films have revealed a close correlation between the chemistry of the hydrocarbon source gases and the coefficients of friction and wear rates of the diamond-like carbon films. Those films grown in source gases with higher hydrogen-to-carbon ratios had much lower coefficients of friction and wear rates than did films derived from source gases with lower hydrogen-to-carbon ratios. The mechanism for this low friction is as yet not properly understood. Ongoing structural characterization of the films at Argonne National Laboratory is gradually revealing this mechanism. Recent studies have included x-ray photoelectron spectroscopy (XPS), near edge x-ray absorption fine structure (NEXAFS) and x-ray reflectivity (XRR). XPS showed {approx}10% oxygen at the surface, which was largely removed after a 1 minute sputter; NEXAFS showed a high sp2:sp3 ratio implying a highly graphitic material; and XRR has given a comprehensive depth profile, with three layers of increasing density as the substrate was approached. The paper discusses the results and correlation with previous friction measurements.
Fundamental characteristics of hybrid X-ray focusing optics for micro X-ray fluorescence analysis
NASA Astrophysics Data System (ADS)
Komatani, Shintaro; Nakamachi, Kazuo; Nakano, Kazuhiko; Ohzawa, Sumito; Uchihara, Hiroshi; Bando, Atsushi; Tsuji, Kouichi
We developed a hybrid X-ray focusing optics, which consisted of a polycapillary X-ray lens (PCXL) and a tungsten conical pinhole (WCP) for micro X-ray fluorescence (?-XRF) analysis. A single PCXL produced an X-ray micro beam with a spot size of 12 ?m. We developed a WCP by using a laser-ablation technique with an input diameter of 39 ?m, an output diameter of 2.5 ?m, and a thickness of 0.5 mm in a conical shape. This hybrid X-ray optics gave a small spot size of 2.8 ?m with a small divergent angle of 12 mrad.
Enhanced x-ray detection sensitivity in semiconducting polymer diodes containing metallic nanoparticles
NASA Astrophysics Data System (ADS)
Mills, Christopher A.; Al-Otaibi, Hulayel; Intaniwet, Akarin; Shkunov, Maxim; Pani, Silvia; Keddie, Joseph L.; Sellin, Paul J.
Semiconducting polymer X-radiation detectors are a completely new family of low-cost radiation detectors with potential application as beam monitors or dosimeters. These detectors are easy to process, mechanically flexible, relatively inexpensive, and able to cover large areas. However, their x-ray photocurrents are typically low as, being composed of elements of low atomic number (Z), they attenuate x-rays weakly. Here, the addition of high-Z nanoparticles is used to increase the x-ray attenuation without sacrificing the attractive properties of the host polymer. Two types of nanoparticles (NPs) are compared: metallic tantalum and electrically insulating bismuth oxide. The detection sensitivity of 5 Ąm thick semiconducting poly([9,9-dioctylfluorenyl-2,7-diyl]-co-bithiophene) diodes containing tantalum NPs is four times greater than that for the analogous NP-free devices; it is approximately double that of diodes containing an equal volume of bismuth oxide NPs. The x-ray induced photocurrent output of the diodes increases with an increased concentration of NPs. However, contrary to the results of theoretical x-ray attenuation calculations, the experimental current output is higher for the lower-Z tantalum diodes than the bismuth oxide diodes, at the same concentration of NP loading. This result is likely due to the higher tantalum NP electrical conductivity, which increases charge transport through the semiconducting polymer, leading to increased diode conductivity.
Leutenegger, Maurice A. [Laboratory for High Energy Astrophysics, Code 662, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Cohen, David H.; MacArthur, James P. [Department of Physics and Astronomy, Swarthmore College, Swarthmore, PA 19081 (United States); Zsargo, Janos [Instituto Politecnico Nacional, Escuela Superior de Fisica y Matematicas, C.P. 07738, Mexico, D. F. (Mexico); Martell, Erin M. [Department of Astronomy, University of Chicago, Chicago, IL 60637 (United States); Owocki, Stanley P. [Bartol Research Institute, University of Delaware, Newark, DE 19716 (United States); Gagne, Marc [Department of Geology and Astronomy, West Chester University of Pennsylvania, West Chester, PA 19383 (United States); Hillier, D. John, E-mail: firstname.lastname@example.com [Department of Physics and Astronomy, University of Pittsburgh, 3941 O'Hara Street, Pittsburgh, PA 15260 (United States)
We present a method for computing the net transmission of X-rays emitted by shock-heated plasma distributed throughout a partially optically thick stellar wind from a massive star. We find the transmission by an exact integration of the formal solution, assuming that the emitting plasma and absorbing plasma are mixed at a constant mass ratio above some minimum radius, below which there is assumed to be no emission. This model is more realistic than either the slab absorption associated with a corona at the base of the wind or the exospheric approximation that assumes that all observed X-rays are emitted without attenuation from above the radius of optical depth unity. Our model is implemented in XSPEC as a pre-calculated table that can be coupled to a user-defined table of the wavelength-dependent wind opacity. We provide a default wind opacity model that is more representative of real wind opacities than the commonly used neutral interstellar medium (ISM) tabulation. Preliminary modeling of Chandra grating data indicates that the X-ray hardness trend of OB stars with spectral subtype can largely be understood as a wind absorption effect.
Modeling Broadband X-Ray Absorption of Massive Star Winds
NASA Technical Reports Server (NTRS)
Leutenegger, Maurice A.; Cohen,David H.; Zsargo, Janos; Martell, Erin M.; MacArthur, James P.; Owocki, Stanley P.; Gagne, Marc; Hillier, D. John
We present a method for computing the net transition of X-rays emitted by shock-heated plasma distributed throughout a partially optically thick stellar wind from a massive star. We find the transmission by an exact integration of the formal solution, assuming the emitting plasma and absorbing plasma are mixed at a constant mass ratio above some minimum radius, below which there is assumed to be no emission. This model is more realistic than either the slab absorption associated with a corona at the base of the wind or the exospheric approximation that assumes all observed X-rays are emitted without attenuation from above the radius of optical depth unity. Our model is implemented in XSPEC as a pre-calculated table that can be coupled to a user-defined table of the wavelength dependent wind opacity. We provide a default wind opacity model that is more representative of real wind opacities than the commonly used neutral ISM tabulation. Preliminary modeling of Chandra grating data indicates that the X-ray hardness trend of OB stars with spectral subtype cars largely be understood as a wind absorption effect.
X-Ray Variability Characteristics of the Seyfert 1 Galaxy NGC 3783
A. Markowitz
We have characterized the energy-dependent X-ray variability properties of the Seyfert 1 galaxy NGC 3783 using archival XMM-Newton and Rossi X-Ray Timing Explorer data. The high-frequency fluctuation power spectral density function (PSD) slope is consistent with flattening toward higher energies. Light-curve cross-correlation functions yield no significant lags, but peak coefficients generally decrease as energy separation of the bands increases on
Microbubbles as a scattering contrast agent for grating-based x-ray dark-field imaging
NASA Astrophysics Data System (ADS)
Velroyen, A.; Bech, M.; Malecki, A.; Tapfer, A.; Yaroshenko, A.; Ingrisch, M.; Cyran, C. C.; Auweter, S. D.; Nikolaou, K.; Reiser, M.; Pfeiffer, F.
In clinically establishedŚabsorption-basedŚbiomedical x-ray imaging, contrast agents with high atomic numbers (e.g. iodine) are commonly used for contrast enhancement. The development of novel x-ray contrast modalities such as phase contrast and dark-field contrast opens up the possible use of alternative contrast media in x-ray imaging. We investigate using ultrasound contrast agents, which unlike iodine-based contrast agents can also be administered to patients with renal impairment and thyroid dysfunction, for application with a recently developed novel x-ray dark-field imaging modality. To produce contrast from these microbubble-based contrast agents, our method exploits ultra-small-angle coherent x-ray scattering. Such scattering dark-field x-ray images can be obtained with a grating-based x-ray imaging setup, together with refraction-based differential phase-contrast and the conventional attenuation contrast images. In this work we specifically show that ultrasound contrast agents based on microbubbles can be used to produce strongly enhanced dark-field contrast, with superior contrast-to-noise ratio compared to the attenuation signal. We also demonstrate that this method works well with an x-ray tube-based setup and that the relative contrast gain even increases when the pixel size is increased from tenths of microns to clinically compatible detector resolutions about up to a millimetre.
A method for normalization of X-ray absorption spectra
Weng, T.-C.; Waldo, G.S.; Penner-Hahn, J.E. (Michigan)
Accurate normalization of X-ray absorption data is essential for quantitative analysis of near-edge features. A method, implemented as the program MBACK, to normalize X-ray absorption data to tabulated mass absorption coefficients is described. Comparison of conventional normalization methods with MBACK demonstrates that the new normalization method is not sensitive to the shape of the background function, thus allowing accurate comparison of data collected in transmission mode with data collected using fluorescence ion chambers or solid-state fluorescence detectors. The new method is shown to have better reliability and consistency and smaller errors than conventional normalization methods. The sensitivity of the new normalization method is illustrated by analysis of data collected during an equilibrium titration.
Recent X-ray Variability of Eta Car Approaching The X-ray Eclipse
NASA Technical Reports Server (NTRS)
Corcoran, M.; Swank, J. H.; Ishibashi, K.; Gull, T.; Humphreys, R.; Damineli, A.; Walborn, N.; Hillier, D. J.; Davidson, K.; White, S. M.
We discuss recent X-ray spectral variability of the supermassive star Eta Car in the interval since the last X-ray eclipse in 1998. We concentrate on the interval just prior to the next X-ray eclipse which is expected to occur in June 2003. We compare the X-ray behavior during the 2001-2003 cycle with the previous cycle (1996-1998) and note similarities and differences in the temporal X-ray behavior. We also compare a recent X-ray observation of Eta Car obtained with the Chandra high energy transmission grating in October 2002 with an earlier observation from Nov 2002, and interpret these results in terms of the proposed colliding wind binary model for the star. In addition we discuss planned observations for the upcoming X-ray eclipse.
Proton-induced x-ray fluorescence CT imaging
Bazalova-Carter, Magdalena; Ahmad, Moiz; Matsuura, Taeko; Takao, Seishin; Matsuo, Yuto; Fahrig, Rebecca; Shirato, Hiroki; Umegaki, Kikuo; Xing, Lei
Purpose: To demonstrate the feasibility of proton-induced x-ray fluorescence CT (pXFCT) imaging of gold in a small animal sized object by means of experiments and Monte Carlo (MC) simulations. Methods: First, proton-induced gold x-ray fluorescence (pXRF) was measured as a function of gold concentration. Vials of 2.2 cm in diameter filled with 0%¢5% Au solutions were irradiated with a 220 MeV proton beam and x-ray fluorescence induced by the interaction of protons, and Au was detected with a 3 ū 3 mm2 CdTe detector placed at 90░ with respect to the incident proton beam at a distance of 45 cm from the vials. Second, a 7-cm diameter water phantom containing three 2.2-diameter vials with 3%¢5% Au solutions was imaged with a 7-mm FWHM 220 MeV proton beam in a first generation CT scanning geometry. X-rays scattered perpendicular to the incident proton beam were acquired with the CdTe detector placed at 45 cm from the phantom positioned on a translation/rotation stage. Twenty one translational steps spaced by 3 mm at each of 36 projection angles spaced by 10░ were acquired, and pXFCT images of the phantom were reconstructed with filtered back projection. A simplified geometry of the experimental data acquisition setup was modeled with the MC TOPAS code, and simulation results were compared to the experimental data. Results: A linear relationship between gold pXRF and gold concentration was observed in both experimental and MC simulation data (R2 > 0.99). All Au vials were apparent in the experimental and simulated pXFCT images. Specifically, the 3% Au vial was detectable in the experimental [contrast-to-noise ratio (CNR) = 5.8] and simulated (CNR = 11.5) pXFCT image. Due to fluorescence x-ray attenuation in the higher concentration vials, the 4% and 5% Au contrast were underestimated by 10% and 15%, respectively, in both the experimental and simulated pXFCT images. Conclusions: Proton-induced x-ray fluorescence CT imaging of 3%¢5% gold solutions in a small animal sized water phantom has been demonstrated for the first time by means of experiments and MC simulations. PMID:25652502
GEMS x-ray polarimeter performance simulations
NASA Astrophysics Data System (ADS)
Baumgartner, Wayne H.; Strohmayer, Tod; Kallman, Tim; Black, J. Kevin; Hill, Joanne E.; Swank, Jean H.; Jahoda, Keith M.
The Gravity and Extreme Magnetism Small explorer (GEMS) is an X-ray polarization telescope selected as a NASA small explorer satellite mission. The X-ray Polarimeter on GEMS uses a Time Projection Chamber gas proportional counter to measure the polarization of astrophysical X-rays in the 2-10 keV band by sensing the direction of the track of the primary photoelectron excited by the incident X-ray. We have simulated the expected sensitivity of the polarimeter to polarized X-rays. We use the simulation package Penelope to model the physics of the interaction of the initial photoelectron with the detector gas and to determine the distribution of charge deposited in the detector volume. We then model the charge diffusion in the detector, and produce simulated track images. Within the track reconstruction algorithm we apply cuts on the track shape and focus on the initial photoelectron direction in order to maximize the overall sensitivity of the instrument. Using this technique we have predicted instrument modulation factors ?100 for 100% polarized X-rays ranging from 10% to over 60% across the 2-10 keV X-ray band. We also discuss the simulation program used to develop and model some of the algorithms used for triggering, and energy measurement of events in the polarimeter.
Toward Adaptive X-Ray Telescopes
NASA Technical Reports Server (NTRS)
O'Dell, Stephen L.; Atkins, Carolyn; Button, Tim W.; Cotroneo, Vincenzo; Davis, William N.; Doel, Peer; Feldman, Charlotte H.; Freeman, Mark D.; Gubarev, Mikhail V.; Kolodziejczak, Jeffrey J.; Michette, Alan G.; Ramsey, Brian D.; Reid, Paul B.; Rodriguez Sanmartin, Daniel; Saha, Timo T.; Schwartz, Daniel A.; Trolier-McKinstry, Susan; Wilke, Rudeger H. T.; Willingale, Richard; Zhang, William W.
Future x-ray observatories will require high-resolution (less than 1 inch) optics with very-large-aperture (greater than 25 square meter) areas. Even with the next generation of heavy-lift launch vehicles, launch-mass constraints and aperture-area requirements will limit the surface areal density of the grazing-incidence mirrors to about 1 kilogram per square meter or less. Achieving sub-arcsecond x-ray imaging with such lightweight mirrors will require excellent mirror surfaces, precise and stable alignment, and exceptional stiffness or deformation compensation. Attaining and maintaining alignment and figure control will likely involve adaptive (in-space adjustable) x-ray optics. In contrast with infrared and visible astronomy, adaptive optics for x-ray astronomy is in its infancy. In the middle of the past decade, two efforts began to advance technologies for adaptive x-ray telescopes: The Generation-X (Gen-X) concept studies in the United States, and the Smart X-ray Optics (SXO) Basic Technology project in the United Kingdom. This paper discusses relevant technological issues and summarizes progress toward adaptive x-ray telescopes.
X-ray monitoring for astrophysical applications
NASA Astrophysics Data System (ADS)
Pina, L.; Burrows, D.; Cash, W.; Cerna, D.; Gorenstein, P.; Hudec, R.; Inneman, A.; Jakubek, J.; Marsikova, V.; Sieger, L.; Tichy, V.
This work addresses the issue of X-ray monitoring for astrophysical applications. The proposed wide-field optical system has not been used in space yet. The proposed novel approach is based on the use of 1D "Lobster eye" optics in combination with Timepix X-ray detector in the energy range 3 - 40 keV. The proposed project includes theoretical study and a functional sample of the Timepix X-ray detector with multifoil wide-field X-ray "Lobster eye" optics. Using optics to focus X-rays on a detector is the only solution in cases the intensity of impinging X-ray radiation is below the sensitivity of the detector, e.g. while monitoring astrophysical objects in space, or phenomena in the Earth's atmosphere. The optical system could be used in a student rocket experiment at University of Colorado. Ideal opportunity is to extend the CubeSat of Pennsylvania State University with the hard X-ray telescope demonstrator consisting of an optical module and Timepix detector.
Toward Active X-ray Telescopes II
NASA Technical Reports Server (NTRS)
O'Dell, Stephen L.; Aldroft, Thomas L.; Atkins, Carolyn; Button, Timothy W.; Cotroneo, Vincenzo; Davis, William N.; Doel, Peter; Feldman, Charlotte H.; Freeman, Mark D.; Gubarev, Mikhail V.; Johnson-Wilke, Raegan L.; Kolodziejczak, Jeffery J.; Lillie, Charles F.; Michette, Alan G.; Ramsey, Brian D.; Reid, Paul B.; Sanmartin, Daniel Rodriguez; Saha, Timo T.; Schwartz, Daniel A.; Trolier-McKinstry, Susan E.; Ulmer, Melville P.; Wilke, Rudeger H. T.; Willingale, Richard; Zhang, William W.
In the half century since the initial discovery of an astronomical (non-solar) x-ray source, the sensitivity for detection of cosmic x-ray sources has improved by ten orders of magnitude. Largely responsible for this dramatic progress has been the refinement of the (grazing-incidence) focusing x-ray telescope. The future of x-ray astronomy relies upon the development of x-ray telescopes with larger aperture areas (greater than 1 m2) and finer angular resolution (less than 1.). Combined with the special requirements of grazing-incidence optics, the mass and envelope constraints of space-borne telescopes render such advances technologically challenging.requiring precision fabrication, alignment, and assembly of large areas (greater than 100 m2) of lightweight (approximately 1 kg m2 areal density) mirrors. Achieving precise and stable alignment and figure control may entail active (in-space adjustable) x-ray optics. This paper discusses relevant programmatic and technological issues and summarizes progress toward active x-ray telescopes.
Supergiant X-Ray Binaries Observed by Suzaku
NASA Technical Reports Server (NTRS)
Bodaghee, A.; Tomsick, J. A.; Rodriquez, J.; Chaty, S.; Pottschmidt, K.; Walter, R.; Romano, P.
Suzaku observations are presented for the high-mass X-ray binaries IGR 116207-5129 and IGR 117391-3021. For IGR 116207-5129, we provide the first X-ray broadband (0.5-60 keV) spectrum from which we confirm a large intrinsic column density (N(sub H) = 1.6 x 10(exp 23)/sq cm), and we constrain the cutoff energy for the first time (E(sub cut) = 19 keV). A prolonged (> 30 ks) attenuation of the X-ray flux was observed which we tentatively attribute to an eclipse of the probable neutron star by its massive companion, in a binary system with an orbital period between 4 and 9 days, and inclination angles> 50 degrees. For IGRJ17391-3021, we witnessed a transition from quiescence to a low-activity phase punctuated by weak flares whose peak luminosities in the 0.5-10keV band are only a factor of 5 times that of the pre-flare emission. These micro flares are accompanied by an increase in NH which suggests the accretion of obscuring clumps of wind. We now recognize that these low-activity epochs constitute the most common emission phase for this system, and perhaps in other supergiant fast X-ray transients (SFXTs) as well. We close with an overview of our upcoming program in which Suzaku will provide the first ever observation of an SFXT (IGRJ16479-4514) during a binary orbit enabling us to probe the accretion wind at every phase.
Globular cluster x-ray sources
Pooley, David
Globular clusters and x-ray astronomy have a long and fruitful history. Uhuru and OSO-7 revealed highly luminous (>Ā1036Āergs-1) x-ray sources in globular clusters, and Einstein and ROSAT revealed a larger population of low-luminosity (<Ā1033Āergs-1) x-ray sources. It was realized early on that the high-luminosity sources were low-mass x-ray binaries in outburst and that they were orders of magnitude more abundant per unit mass in globular clusters than in the rest of the galaxy. However, the low-luminosity sources proved difficult to classify. Many ideas were put forthŚlow-mass x-ray binaries in quiescence (qLMXBs), cataclysmic variables (CVs), active main-sequence binaries (ABs), and millisecond pulsars (MSPs)Śbut secure identifications were scarce. In ROSAT observations of 55 clusters, about 25 low-luminosity sources were found. Chandra has now observed over 80 Galactic globular clusters, and these observations have revealed over 1,500 x-ray sources. The superb angular resolution has allowed for many counterpart identifications, providing clues to the nature of this population. It is a heterogeneous mix of qLMXBs, CVs, ABs, and MSPs, and it has been shown that the qLMXBs and CVs are both, in part, overabundant like the luminous LMXBs. The number of x-ray sources in a cluster correlates very well with its encounter frequency. This points to dynamical formation scenarios for the x-ray sources and shows them to be excellent tracers of the complicated internal dynamics. The relation between the encounter frequency and the number of x-ray sources has been used to suggest that we have misunderstood the dynamical states of globular clusters. PMID:20404204
Globular cluster x-ray sources
NASA Astrophysics Data System (ADS)
Pooley, David
Globular clusters and x-ray astronomy have a long and fruitful history. Uhuru and OSO-7 revealed highly luminous (> 1036 ergs-1) x-ray sources in globular clusters, and Einstein and ROSAT revealed a larger population of low-luminosity (< 1033 ergs-1) x-ray sources. It was realized early on that the high-luminosity sources were low-mass x-ray binaries in outburst and that they were orders of magnitude more abundant per unit mass in globular clusters than in the rest of the galaxy. However, the low-luminosity sources proved difficult to classify. Many ideas were put forth - low-mass x-ray binaries in quiescence (qLMXBs), cataclysmic variables (CVs), active main-sequence binaries (ABs), and millisecond pulsars (MSPs) - but secure identifications were scarce. In ROSAT observations of 55 clusters, about 25 low-luminosity sources were found. Chandra has now observed over 80 Galactic globular clusters, and these observations have revealed over 1,500 x-ray sources. The superb angular resolution has allowed for many counterpart identifications, providing clues to the nature of this population. It is a heterogeneous mix of qLMXBs, CVs, ABs, and MSPs, and it has been shown that the qLMXBs and CVs are both, in part, overabundant like the luminous LMXBs. The number of x-ray sources in a cluster correlates very well with its encounter frequency. This points to dynamical formation scenarios for the x-ray sources and shows them to be excellent tracers of the complicated internal dynamics. The relation between the encounter frequency and the number of x-ray sources has been used to suggest that we have misunderstood the dynamical states of globular clusters.
Globular cluster x-ray sources.
Pooley, David
Globular clusters and x-ray astronomy have a long and fruitful history. Uhuru and OSO-7 revealed highly luminous (> 10(36) ergs(-1)) x-ray sources in globular clusters, and Einstein and ROSAT revealed a larger population of low-luminosity (< 10(33) ergs(-1)) x-ray sources. It was realized early on that the high-luminosity sources were low-mass x-ray binaries in outburst and that they were orders of magnitude more abundant per unit mass in globular clusters than in the rest of the galaxy. However, the low-luminosity sources proved difficult to classify. Many ideas were put forth--low-mass x-ray binaries in quiescence (qLMXBs), cataclysmic variables (CVs), active main-sequence binaries (ABs), and millisecond pulsars (MSPs)--but secure identifications were scarce. In ROSAT observations of 55 clusters, about 25 low-luminosity sources were found. Chandra has now observed over 80 Galactic globular clusters, and these observations have revealed over 1,500 x-ray sources. The superb angular resolution has allowed for many counterpart identifications, providing clues to the nature of this population. It is a heterogeneous mix of qLMXBs, CVs, ABs, and MSPs, and it has been shown that the qLMXBs and CVs are both, in part, overabundant like the luminous LMXBs. The number of x-ray sources in a cluster correlates very well with its encounter frequency. This points to dynamical formation scenarios for the x-ray sources and shows them to be excellent tracers of the complicated internal dynamics. The relation between the encounter frequency and the number of x-ray sources has been used to suggest that we have misunderstood the dynamical states of globular clusters. PMID:20404204
Quasar x-ray spectra revisited
NASA Technical Reports Server (NTRS)
Shastri, P.; Wilkes, B. J.; Elvis, M.; Mcdowell, J.
A sample of 45 quasars observed by the Imaging Proportional Counter (IPC) on the Einstein satellite is used to re-examine the relationship between the soft (0.2-3.5 keV) X-ray energy index and radio-loudness. We found the following: (1) the tendency for radio-loud quasars to have systematically flatter X-ray slopes than radio-quiet quasars (RQQ's) is confirmed with the soft X-ray excess having negligible effect; (2) there is a tendency for the flatness of the X-ray slope to correlate with radio core-dominance for radio-loud quasars, suggesting that a component of the X-ray emission is relativistically beamed; (3) for the RQQ's the soft X-ray slopes, with a mean of approximately 1.0, are consistent with the slopes found at higher energies (2-10 keV) although steeper than those observed for Seyfert 1 galaxies (also 2-10 keV) where the reflection model gives a good fit to the data; (4) the correlation of FeII emission line strength with X-ray energy index is confirmed for radio-quiet quasars using a subset of 18 quasars. The radio-loud quasars show no evidence for a correlation. This relation suggests a connection between the ionizing continuum and the line emission from the broad emission line region (BELR) of radio-quiet quasars, but in the opposite sense to that predicted by current photoionization models; and (5) the correlations of X-ray slope with radio core dominance and FeII equivalent width within the radio-loud and radio-quiet sub-classes respectively imply that the observed wide range of X-ray spectral slopes is real rather than due to the large measuring uncertainties for individual objects.
Changes in the linear attenuation coefficient of canine appendicular bone following intravenous infusion of strontium lactate, measured using gamma-ray computed tomography
Thomas R. Overton; Richard E. Snyder; Thomas N. Hangartner; Safwat Girgis; Robert J. Audette; David C. Secord
Changes in the average linear attenuation coefficient (LAC) within a fixed measurement volume in the proximal end of the dog tibia, which contains trabecular bone and associated soft tissues (the trabecular bone ōspaceö), were monitored continuously using gamma-ray computed tomography (?-CT) prior to, during, and following intravenous infusion of strontium (Sr) lactate. An infusion of 1.3¢4.7 g of Sr over
Measurement of attenuation coefficients for bone, muscle, fat and water at 140, 364 and 662 keV gamma-ray energies
A. Akar; H. Baltas; U. Ūevik; F. Korkmaz; N. T. Okumusoglu
The half-value thicknesses, linear and mass attenuation coefficients of biological samples such as bone, muscle, fat and water have been measured at 140, 364 and 662 keV gamma-ray energies by using the ATOMLABTM-930 medical spectrometer. The gamma-rays were obtained from 99mTc, 131I and 137Cs gamma-ray point sources. Also theoretical calculations have been performed in order to obtain the half-value thicknesses
Use of Electromagnetic Acoustic Resonance Method to Detect Micro-Voids Via Evaluation of Ultrasonic Wave Attenuation Coefficient of SUS304 Steel Fabricated by Hot Isostatic Press
Hidetaka Nishida; Hiroshi Yamaguchi; Masashi Yoshida
Creep damage in SUS304 steel samples fabricated by a hot isostatic press (HIP) at 1050░C was evaluated using the electromagnetic acoustic resonance (EMAR), noise energy and ultrasonic spectroscopy (first moment) methods. The coefficients of attenuation of 1.1 to 5.4 MHz electromagnetically excited acoustic waves in the samples were investigated. By reducing diffraction loss and the loss to the electromagnetic acoustic
Materials for refractive x-ray optics.
Lund, M W
An X-ray lens using refraction has been proposed by Tomie, and demonstrated for 14 keV X-rays by Snigirev et al. This type of lens is made from a series of very weak lens elements. I calculate the properties of such lenses constructed of various chemical elements and compounds over the range of 1 to 30 keV. In general, I find that X-ray optics made from low density, low Z materials have the widest useful apertures, but require more lens elements than denser and higher Z materials. PMID:21311123
X-ray properties of spiral galaxies
Roberto Soria
X-ray studies of nearby spiral galaxies with star formation allow us to investigate temperature and spatial distribution of the hot diffuse plasma, and to carry out individual and statistical studies of different classes of discrete sources (low- and high-mass X-ray binaries, Supernova remnants, supersoft and ultra-luminous sources). In particular, we briefly review the different models proposed to explain the ultra-luminous sources. We can then use the X-ray properties of a galaxy to probe its star formation history. We choose the starburst spiral M83 to illustrate some of these issues.
Large Area X-Ray Spectroscopy Mission
NASA Technical Reports Server (NTRS)
Tananbaum, H.
The Large Area X-ray Spectroscopy (LAXS) mission concept study continues to evolve strongly following the merging of the LAXS mission with the Next Generation X-ray Observatory (NGXO, PI: Nick White) into the re-named High Throughput X-ray Spectroscopy (HTXS) Mission. HTXS retains key elements of the LAXS proposal, including the use of multiple satellites for risk-reduction and cost savings. A key achievement of the program has been the recommendation by the Structure and Evolution of the Universe (SEUS) (April 1997) for a new start for the HTXS mission in the 2000-2004 timeframe.
X-ray line emission from Capella
NASA Astrophysics Data System (ADS)
Holt, S. S.; White, N. E.; Becker, R. H.; Boldt, E. A.; Mushotzky, R. F.; Serlemitsos, P. J.; Smith, B. W.
X-ray emission line components from Mg, Si, S and Fe were unambiguously detected from Capella with the Solid-State Spectrometer onboard the Einstein Observatory. The X-ray spectrum is inconsistent with an isothermal corona, and requires components between 6,000,000 K and at least 24,000,000 K for an adequate fit. An inhomogeneous corona in which the X-ray emitting plasma is confined to magnetically-contained loops appears to be reconcilable with all of the experimental evidence.
X-ray Interferometer Using Prism Optics
Suzuki, Yoshio [JASRI/SPring-8 Mikazuki, Hyogo 6791-5198 (Japan)
Two-beam X-ray interferometer using refractive optics has been developed. A prism made of acrylic resin is used as the beam deflector for hard X-ray wavefront dividing interferometer. This configuration is the same as that of the Fresnel's bi-prism interferometer or the Leith-Upatnieks type two-beam holography in visible light region. Therefore, quantitative analysis of the degree of transversal coherence can be performed by measuring the visibility of interference fringes. It is also possible to realize two-beam holographic imaging in hard X-ray regions.
NASA Astrophysics Data System (ADS)
Haga, A.; Senda, S.; Sakai, Y.; Mizuta, Y.; Kita, S.; Okuyama, F.
A miniature x-ray tube is described. The tube is made of Kovar, inside which a grounded target is located close to a field-electron emitter consisting of aligned carbon nanofibers, which continues to work for around 100 h in the 10-6 Pa region unless arcing is induced between the electrodes. The resolution of the contact x-ray images provided by the tube would be impossible using the existing techniques of conventional x-ray radiography, whether the sample is biological or nonbiological.
NASA Technical Reports Server (NTRS)
Weisskopf, Martin C.
The most important next step is the development of X-ray optics comparable to (or better than) Chandra in angular resolution that far exceed Chandra s effective area. Use the long delay to establish an adequately funded, competitive technology program along the lines I have recommended. Don't be diverted from this objective, except for Explorer-class missions. Progress in X-ray optics, with emphasis on the angular resolution, is central to the paradigm-shifting discoveries and the contributions of X-ray astronomy to multiwavelength astrophysics over the past 51 years.
NSDL National Science Digital Library
Dexter Perkins
This is an x-ray diffraction analysis of six sand samples and comparison with hand specimens. Students look at each of the six samples under the binocular microscope and note such useful properties as number of minerals, cleavage/fracture, color, shape, grain size, roundness, and degree of sorting. Then they grind up small amounts of each sample and mount them on glass slides for X-ray. Students write all sample descriptions and X-ray analysis results in their lab notebook. Then they identify the minerals in each sample, determine where they are from, and write a report summarizing all results.
Calculation of 10 MV x-ray spectra emitted by a medical linear accelerator using the BFGS quasi-Newton method
NASA Astrophysics Data System (ADS)
Shimozato, T.; Tabushi, K.; Kitoh, S.; Shiota, Y.; Hirayama, C.; Suzuki, S.
To calculate photon spectra for a 10 MV x-ray beam emitted by a medical linear accelerator, we performed numerical analysis using the aluminium transmission data obtained along the central axis of the beam under the narrow beam condition corresponding to a 3 ū 3 cm2 field at a 100 cm distance from the source. We used the BFGS quasi-Newton method based on a general nonlinear optimization technique for the numerical analysis. The attenuation coefficients, aluminium thicknesses and measured transmission data are necessary inputs for the numerical analysis. The calculated x-ray spectrum shape was smooth in the lower to higher energy regions without any angular components. The x-ray spectrum acquired by the employed method was evaluated by comparing the measurements along the central axis percentage depth dose in a water phantom and by a Monte Carlo simulation code, the electron gamma shower code. The values of the calculated percentage depth doses for a 10 ū 10 cm2 field at a 100 cm source-to-surface distance in a water phantom were obtained using the same geometry settings as those of the water phantom measurement. The differences in the measured and calculated values were less than ▒1.0% for a broad region from the shallow part near the surface to deep parts of up to 25 cm in the water phantom.
Calculation of 10 MV x-ray spectra emitted by a medical linear accelerator using the BFGS quasi-Newton method.
Shimozato, T; Tabushi, K; Kitoh, S; Shiota, Y; Hirayama, C; Suzuki, S
To calculate photon spectra for a 10 MV x-ray beam emitted by a medical linear accelerator, we performed numerical analysis using the aluminium transmission data obtained along the central axis of the beam under the narrow beam condition corresponding to a 3x3 cm2 field at a 100 cm distance from the source. We used the BFGS quasi-Newton method based on a general nonlinear optimization technique for the numerical analysis. The attenuation coefficients, aluminium thicknesses and measured transmission data are necessary inputs for the numerical analysis. The calculated x-ray spectrum shape was smooth in the lower to higher energy regions without any angular components. The x-ray spectrum acquired by the employed method was evaluated by comparing the measurements along the central axis percentage depth dose in a water phantom and by a Monte Carlo simulation code, the electron gamma shower code. The values of the calculated percentage depth doses for a 10x10 cm2 field at a 100 cm source-to-surface distance in a water phantom were obtained using the same geometry settings as those of the water phantom measurement. The differences in the measured and calculated values were less than +/-1.0% for a broad region from the shallow part near the surface to deep parts of up to 25 cm in the water phantom. PMID:17202630
Optimization of phosphor screens for charge coupled device based detectors and 7-34 keV x-rays
NASA Astrophysics Data System (ADS)
Wang, P.-C.; Cargill, G. S., III
Phosphor screens which convert x-ray images to visible light images are key components in two-dimensional charge coupled device (CCD) based detector systems used for x-ray diffraction. Some experimental and theoretical aspects of phosphor screen performance are described in this article. The efficiencies of x-ray-to-light conversion were measured using a CCD camera for transmission phosphor screens fabricated from two different phosphor powders, Y2O2S:Eu (P22R) and Gd2O2S:Tb (P43), for screen mass thicknesses of 3-50 mg/cm2 and for x-ray energies of 7-34 keV. A model was developed and evaluated for the dependence of the emitted light brightness on screen thickness and x-ray energy. Inputs to the model are x-ray absorption coefficients available from published compilations, and light attenuation versus thickness data, which were determined experimentally for the phosphors and found to be dominated by scattering rather than absorption. The angular distribution of emitted light, measured for one of the phosphor screens, was found to be nearly Lambertian. Broadening of image features in the x-ray-to-visible-light conversion by phosphors for 19.6 keV x-rays was found to increase approximately linearly with phosphor screen thicknesses in the range of 30-160 ?m, but with a minimum width of 110 ?m for P22R phosphor and 70 ?m for P43 phosphor. In the range of 7-15 keV, maximum brightness was obtained for P43 phosphor screens of about 10 mg/cm2 mass thickness (60 ?m). For P22R screens, the thickness for maximum brightness increased from about 8 mg/cm2 (50 ?m) for 7 keV to more than 46 mg/cm2 (210 ?m) for 15 keV. For 7 keV the maximum brightnesses for P22R and P43 phosphors were about the same. For 10 keV the maximum brightness for P43 phosphor was about 60% greater than the maximum brightness for P22R phosphor samples tested. For 15 keV the maximum brightness for P43 phosphor was again about 60% greater than that for the P22R samples tested. In the range of 20-34 keV, maximum brightness would occur for thicknesses greater than 46 mg/cm2 (210 ?m) for P22R phosphor and greater than 40 mg/cm2 (160 ?m) for P43 phosphor. Comparing the brightness for 90 ?m thickness for the two phosphors, P43 was about 30% brighter for 20 keV, 20% brighter for 24 keV, and 10% brighter for both 29 and 34 keV.
Engine materials characterization and damage monitoring by using x ray technologies
NASA Technical Reports Server (NTRS)
Baaklini, George Y.
X ray attenuation measurement systems that are capable of characterizing density variations in monolithic ceramics and damage due to processing and/or mechanical testing in ceramic and intermetallic matrix composites are developed and applied. Noninvasive monitoring of damage accumulation and failure sequences in ceramic matrix composites is used during room-temperature tensile testing. This work resulted in the development of a point-scan digital radiography system and an in situ x ray material testing system. The former is used to characterize silicon carbide and silicon nitride specimens, and the latter is used to image the failure behavior of silicon-carbide-fiber-reinforced, reaction-bonded silicon nitride matrix composites. State-of-the-art x ray computed tomography is investigated to determine its capabilities and limitations in characterizing density variations of subscale engine components (e.g., a silicon carbide rotor, a silicon nitride blade, and a silicon-carbide-fiber-reinforced beta titanium matrix rod, rotor, and ring). Microfocus radiography, conventional radiography, scanning acoustic microscopy, and metallography are used to substantiate the x ray computed tomography findings. Point-scan digital radiography is a viable technique for characterizing density variations in monolithic ceramic specimens. But it is very limited and time consuming in characterizing ceramic matrix composites. Precise x ray attenuation measurements, reflecting minute density variations, are achieved by photon counting and by using microcollimators at the source and the detector. X ray computed tomography is found to be a unique x ray attenuation measurement technique capable of providing cross-sectional spatial density information in monolithic ceramics and metal matrix composites. X ray computed tomography is proven to accelerate generic composite component development. Radiographic evaluation before, during, and after loading shows the effect of preexisting volume flaws on the fracture behavior of composites. Results from one-, three-, five-, and eight-ply ceramic composite specimens show that x ray film radiography can monitor damage accumulation during tensile loading. Matrix cracking, fiber-matrix debonding, fiber bridging, and fiber pullout are imaged throughout the tensile loading of the specimens. In situ film radiography is found to be a practical technique for estimating interfacial shear strength between the silicon carbide fibers and the reaction-bonded silicon nitride matrix. It is concluded that pretest, in situ, and post-test x ray imaging can provide greater understanding of ceramic matrix composite mechanical behavior.
"X-Ray Transients in Star-Forming Regions" and "Hard X-Ray Emission from X-Ray Bursters"
NASA Technical Reports Server (NTRS)
Halpern, Jules P.; Kaaret, Philip
This grant funded work on the analysis of data obtained with the Burst and Transient Experiment (BATSE) on the Compton Gamma-Ray Observatory. The goal of the work was to search for hard x-ray transients in star forming regions using the all-sky hard x-ray monitoring capability of BATSE. Our initial work lead to the discovery of a hard x-ray transient, GRO J1849-03. Follow-up observations of this source made with the Wide Field Camera on BeppoSAX showed that the source should be identified with the previously known x-ray pulsar GS 1843-02 which itself is identified with the x-ray source X1845-024 originally discovered with the SAS-3 satellite. Our identification of the source and measurement of the outburst recurrence time, lead to the identification of the source as a Be/X-ray binary with a spin period of 94.8 s and an orbital period of 241 days. The funding was used primarily for partial salary and travel support for John Tomsick, then a graduate student at Columbia University. John Tomsick, now Dr. Tomsick, received his Ph.D. from Columbia University in July 1999, based partially on results obtained under this investigation. He is now a postdoctoral research scientist at the University of California, San Diego.
Talbot phase-contrast x-ray imaging for the small joints of the hand
NASA Astrophysics Data System (ADS)
Stutman, Dan; Beck, Thomas J.; Carrino, John A.; Bingham, Clifton O.
A high-resolution radiographic method for soft tissues in the small joints of the hand would aid in the study and treatment of rheumatoid arthritis (RA) and osteoarthritis (OA), which often attacks these joints. Of particular interest would be imaging with <100 Ąm resolution the joint cartilage, whose integrity is a main indicator of disease. Differential phase-contrast (DPC) or refraction-based x-ray imaging with Talbot grating interferometers could provide such a method, since it enhances soft tissue contrast and can be implemented with conventional x-ray tubes. A numerical joint phantom was first developed to assess the angular sensitivity and spectrum needed for a hand DPC system. The model predicts that, due to quite similar refraction indexes for joint soft tissues, the refraction effects are very small, requiring high angular resolution. To compare our model to experiment we built a high-resolution bench-top interferometer using 10 Ąm period gratings, a W anode tube and a CCD-based detector. Imaging experiments on animal cartilage and on a human finger support the model predictions. For instance, the estimated difference between the index of refraction of cartilage and water is of only several percent at ~25 keV mean energy, comparable to that between the linear attenuation coefficients. The potential advantage of DPC imaging thus comes mainly from the edge enhancement at the soft tissue interfaces. Experiments using a cadaveric human finger are also qualitatively consistent with the joint model, showing that refraction contrast is dominated by tendon embedded in muscle, with the cartilage layer difficult to observe in our conditions. Nevertheless, the model predicts that a DPC radiographic system for the small hand joints of the hand could be feasible using a low energy quasi-monochromatic source, such as a K-edge filtered Rh or Mo tube, in conjunction with a ~2 m long 'symmetric' interferometer operated in a high Talbot order.
Talbot phase-contrast x-ray imaging for the small joints of the hand.
Stutman, Dan; Beck, Thomas J; Carrino, John A; Bingham, Clifton O
A high-resolution radiographic method for soft tissues in the small joints of the hand would aid in the study and treatment of rheumatoid arthritis (RA) and osteoarthritis (OA), which often attacks these joints. Of particular interest would be imaging with <100 Ąm resolution the joint cartilage, whose integrity is a main indicator of disease. Differential phase-contrast (DPC) or refraction-based x-ray imaging with Talbot grating interferometers could provide such a method, since it enhances soft tissue contrast and can be implemented with conventional x-ray tubes. A numerical joint phantom was first developed to assess the angular sensitivity and spectrum needed for a hand DPC system. The model predicts that, due to quite similar refraction indexes for joint soft tissues, the refraction effects are very small, requiring high angular resolution. To compare our model to experiment we built a high-resolution bench-top interferometer using 10 Ąm period gratings, a W anode tube and a CCD-based detector. Imaging experiments on animal cartilage and on a human finger support the model predictions. For instance, the estimated difference between the index of refraction of cartilage and water is of only several percent at ?25 keV mean energy, comparable to that between the linear attenuation coefficients. The potential advantage of DPC imaging thus comes mainly from the edge enhancement at the soft tissue interfaces. Experiments using a cadaveric human finger are also qualitatively consistent with the joint model, showing that refraction contrast is dominated by tendon embedded in muscle, with the cartilage layer difficult to observe in our conditions. Nevertheless, the model predicts that a DPC radiographic system for the small hand joints of the hand could be feasible using a low energy quasi-monochromatic source, such as a K-edge filtered Rh or Mo tube, in conjunction with a ?2 m long 'symmetric' interferometer operated in a high Talbot order. PMID:21841214
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X-Ray Shawdowgraph Camera Design
Edward J. McCrea; Michael J. Doman; Randy A. Rohde
An imagining camera that is used with X-Ray radiography systems in high explosive experiments has been built and fielded. The camera uses a 40mm diameter Micro-Channel Plate Itensifier (MCPI) for optical gain and photographic film for image recording. In the normal location of the X-ray film pack, a scintillating screen is placed instead. The camera system views the screen and records the image. The sensitivity of the MCPI to light makes the camera design sensitive to small details that a film pack does not need to consider. The X-ray image recording system was designed and bulit for situations where the film pack of the X-ray shadowgraph is not retrievable after the experiment. The system has been used in a number of experiments.
Marton, J. [Stefan Meyer Institute of the Austrian Academy of Sciences, 1090 Vienna, Boltzmnanngasse 3 (Austria)
In kaonic atoms energy displacement and broadening of states result from the strong interaction. The most simple kaonic atoms like kaonic hydrogen and deuterium open the possibility to measure this strong interaction induced shift and width by x-ray spectroscopy. In the SIDDHARTA experiment al LNF (Frascati) the DA{phi}NE electron-positron collider delivers nearly mono-energetic negatively charged kaons from {phi} meson decay. This unique kaon source is used to form kaonic atoms. New high performance x-ray detectors (silicon drift detectors) arranged in an array allow x-ray spectroscopy with high energy resolution combined with timing capability. High precision x-ray measurements like SIDDHARTA at LNF will open the way to study the low energy regime of the strong force in the antikaon-nucleon interaction. The experiment and its current status is presented in this talk.
Holding X-Ray Film Inside Ducts
NASA Technical Reports Server (NTRS)
Bulthuis, Ronald V.; Pierce, Darryl
Radiographic inspection of welds in walls of nonmagnetic ducts made easy by new film holder. X-Ray film inside duct held by interior and exterior magnets. Tether used to move holder and to retrieve it from inside duct.
Chandra X-Ray Observatory Center
NSDL National Science Digital Library
This week, Space Shuttle mission STS-93 deployed the Chandra X-Ray Observatory, the world's most powerful X-Ray telescope. The third of NASA's "Great Observatories," the Chandra X-Ray Observatory will study X-Rays rather than visible light (the Hubble Space Telescope) or gamma rays (the Compton Gamma Ray Observatory). This site offers overviews and news of the Observatory and its mission. Operated for NASA by the Harvard-Smithsonian Center for Astrophysics, this site provides resources for students, scientists, the press, and general users. In the Public Information and Education section, users will find photos, a field guide, and educational materials. The Scientific User Support Section includes detailed target information, various documents, newsletters, and information on the Emission Line Project (ELP). In addition, the site provides breaking mission news, links to live video feeds, telemetry diagrams, and a timeline.
Logan, C.M.
An x-ray source is described utilizing anode material which shifts the output spectrum to higher energy and thereby obtains higher penetrating ability for screening mammography application, than the currently utilized anode material. The currently used anode material (molybdenum) produces an energy x-ray spectrum of 17.5/19.6 keV, which using the anode material of this invention (e.g. silver, rhodium, and tungsten) the x-ray spectrum would be in the 20-35 keV region. Thus, the anode material of this invention provides for imaging of breasts with higher than average x-ray opacity without increase of the radiation dose, and thus reduces the risk of induced breast cancer due to the radiation dose administered for mammograms. 6 figures.
X-ray transmission microscope development
NASA Technical Reports Server (NTRS)
Kaukler, William F.; Rosenberger, Franz E.
This report covers the third 6 month period, from February 28, 1995 to August 31, 1995, under this contract. The main efforts during this period were the construction of the X-ray furnace, evaluation and selection of the CCD technology for the X-ray camera, solidification experiments with Al alloys and Al-zirconia composites in the prototype furnace, evaluation of specimens for the particle pushing flight experiment - PEPSI, measurements of emitted spectra from X-ray source, testing of the high resolution X-ray test targets, and the establishment of criteria for and selection of peripheral equipment. In addition to these tasks, two presentations were prepared in this period; one for the AIAA Microgravity Symposium and another for the Gordon Conference on Gravitational Effects in Pyisico-Chemical Systems.
X ray opacity in cluster cooling flows
NASA Technical Reports Server (NTRS)
Wise, Michael W.; Sarazin, Craig L.
We have calculated the emergent x-ray properties for a set of spherically symmetric, steady-state cluster cooling flow models including the effects of radiative transfer. Opacity due to resonant x-ray lines, photoelectric absorption, and electron scattering have been included in these calculations, and homogeneous and inhomogeneous gas distributions were considered. The effects of photoionization opacity are small for both types of models. In contrast, resonant line optical depths can be quite high in both homogeneous and inhomogeneous models. The presence of turbulence in the gas can significantly lower the line opacity. We find that integrated x-ray spectra for the flow cooling now are only slightly affected by radiative transfer effects. However x-ray line surface brightness profiles can be dramatically affected by radiative transfer. Line profiles are also strongly affected by transfer effects. The combined effects of opacity and inflow cause many of the lines in optically thick models to be asymmetrical.
Logan, Clinton M. (Pleasanton, CA)
An x-ray source utilizing anode material which shifts the output spectrum to higher energy and thereby obtains higher penetrating ability for screening mammography application, than the currently utilized anode material. The currently used anode material (molybdenum) produces an energy x-ray spectrum of 17.5/19.6 keV, which using the anode material of this invention (e.g. silver, rhodium, and tungsten) the x-ray spectrum would be in the 20-35 keV region. Thus, the anode material of this invention provides for imaging of breasts with higher than average x-ray opacity without increase of the radiation dose, and thus reduces the risk of induced breast cancer due to the radiation dose administered for mammograms.
Coherent x-ray lasers for applications
London, R.A.; Amendt, P.; Rosen, M.D.; Feit, M.D.; Fleck, J.A. (Lawrence Livermore National Lab., CA (USA)); Strauss, M. (Negev Nuclear Research Centre, Beersheba (Israel))
Many of the projected applications of x-ray lasers require high quality output radiation with properties such as short wavelength, high power, good focusability, short pulse, and high degree of coherence. We discuss the requirements of an x-ray laser for the application of holography of biological samples. We present ideas for achieving these properties. Given that population inversions can be established to provide laser gain, we discuss how the propagation and amplification of x-rays within the lasing medium affect the quality of the output radiation. Particular attention is given toward the development of transverse coherence. Results are presented from several methods for calculating the coherence, including a modal analysis and a numerical-wave propagation code. Calculations of the expected degree of coherence of standard x-ray lasers are given, as well as designs for more coherent lasers. 9 refs., 6 figs., 1 tab.
NASA Astrophysics Data System (ADS)
Senda, S.; Sakai, Y.; Mizuta, Y.; Kita, S.; Okuyama, F.
A transmission x-ray tube super-miniature in size is described. The x-ray tube is 5mm in diameter, and comprised of a built-in electron-emitter assembly and a grounded planar target. The key component of the emitter assembly is a Kovar pipe 2mm in diameter, inside which carbon nanofibers aligned on an electro-polished molybdenum tip are loaded to serve as the electron emitter. This type of electron emitter is highly robust in non-ultrahigh vacuum, continuing to field emit electrons for 100h or longer at pressures in the 10-5Pa region. This x-ray tube provides clear x-ray images.
Small Angle X-Ray Scattering Detector
Hessler, Jan P.
A detector for time-resolved small-angle x-ray scattering includes a nearly constant diameter, evacuated linear tube having an end plate detector with a first fluorescent screen and concentric rings of first fiber optic bundles for low angle scattering detection and an annular detector having a second fluorescent screen and second fiber optic bundles concentrically disposed about the tube for higher angle scattering detection. With the scattering source, i.e., the specimen under investigation, located outside of the evacuated tube on the tube's longitudinal axis, scattered x-rays are detected by the fiber optic bundles, to each of which is coupled a respective photodetector, to provide a measurement resolution, i.e., dq/q, where q is the momentum transferred from an incident x-ray to an x-ray scattering specimen, of 2% over two (2) orders of magnitude in reciprocal space, i.e., qmax/qmin approx=lO0.
X-ray imaging: Status and trends
Ryon, R.W.; Martz, H.E.; Hernandez, J.M.; Haskins, J.J.; Day, R.A.; Brase, J.M.; Cross, B.; Wherry, D.
There is a veritable renaissance occurring in x-ray imaging. X-ray imaging by radiography has been a highly developed technology in medicine and industry for many years. However, high resolution imaging has not generally been practical because sources have been relatively dim and diffuse, optical elements have been nonexistent for most applications, and detectors have been slow and of low resolution. Materials analysis needs have therefore gone unmet. Rapid progress is now taking place because we are able to exploit developments in microelectronics and related material fabrication techniques, and because of the availability of intense x-ray sources. This report describes the methods and uses of x-ray imaging along with a discussion of technology advances in these areas.
NASA Technical Reports Server (NTRS)
Porter, F. Scott
X-ray calorimeter instruments for astrophysics have seen rapid development since they were invented in 1984. The prime instrument on all currently planned X-ray spectroscopic observatories is based on calorimeter technology. This relatively simple detection concept that senses the energy of an incident photon by measuring the temperature rise of an absorber material at very low temperatures, can form the basis of a very high performance, non-dispersive spectrometer. State-of-the-art calorimeter instruments have resolving powers of over 3000, large simultaneous band-passes, and near unit efficiency. This coupled with the intrinsic imaging capability of a pixilated x-ray calorimeter array, allows true spectral-spatial instruments to be constructed. In this chapter I briefly review the detection scheme, the state-of-the-art in X-ray calorimeter instruments and the future outlook for this technology.
... information you need from the Academy of General Dentistry Wednesday, April 01, 2015 About | Contact InfoBites Quick ... Related Articles: X-Rays The Academy of General Dentistry (AGD) Sets the Record Straight on Dental X- ...
NASA Astrophysics Data System (ADS)
del Zanna, G.; Bromage, G.; Foley, C.; Worters, H.; Mason, H.; Landini, M.
We present preliminary results on new X-ray spectroscopic XMM/RGS observations of the visual binary nicknamed `Horace Horologii' (2RE J0241-53). The two stars are strong and very active X-ray emitters, and are members of an association of Post-T-Tauri stars. A detailed study (in particular in terms of chemical composition) is important for our understanding of the evolution from the T-Tauri phase, and to explain the origin of the X-ray emission in very young stars. The physical characteristics of the quiescent X-ray emission are described, and related to other stellar parameters such as photospheric abundances and the rotational period. Simultaneous ground-based optical spectroscopy and U-band photometric monitoring observations were obtained at the South African Astronomical Observatory.
Tuberculosis, advanced - chest x-rays (image)
Tuberculosis is an infectious disease that causes inflammation, the formation of tubercules and other growths within tissue, ... death. These chest x-rays show advanced pulmonary tuberculosis. There are multiple light areas (opacities) of varying ...
X-ray fluorescence with synchrotron radiation
Jones, K.W.; Gordon, B.M.; Hanson, A.L.; Pounds, J.G.; Schidlovsky, G.
X-ray fluorescence (XRF) has long been used to make measurements of trace element concentrations in biological materials with very high sensitivity. It has not been previously possible to work with micrometer spatial resolutions because of the relatively low brightness of x-ray tubes. This situation is much improved by using synchrotron storage ring x-ray sources since the brightness of the synchrotron source is many orders of magnitude higher than is obtained with the most intense tube sources. These intense sources open the possibility of using the XRF technique for measurements with resolutions of approximately cellular dimensions. A description of a current research project at Brookhaven which uses synchrotron radiation induced x-ray emission (SRIXE) is presented to illustrate a specific application of the method in biology. 1 ref., 4 figs.
NASA Technical Reports Server (NTRS)
Crannell, C. J.; Frost, K. J.; Maetzler, C.; Ohki, K.; Saba, J. L.
A set of 22 simple, impulsive solar flares, identified in the OSO-5 hard X-ray data, were analyzed together with coincident microwave and meterwave radio observations. The rise times and fall times of the X-ray bursts are found to be highly correlated and effectively equal, strongly suggesting a flare energizing mechanism that is reversible. The good time resolution available for these observations reveals that the microwave emission is influenced by an additional process, evident in the tendency of the microwave emission to peak later and decay more slowly than the symmetric X-ray bursts. Meterwave emission is observed in coincidence with the 5 events which show the strongest time correlation between the X-ray and microwave burst structure. This meterwave emission is characterized by U-burst radiation, indicating confinement of the flare source.
X-ray transmission microscope development
NASA Astrophysics Data System (ADS)
Kaukler, William F.; Rosenberger, Franz E.
This report covers the third 6 month period, from February 28, 1995 to August 31, 1995, under this contract. The main efforts during this period were the construction of the X-ray furnace, evaluation and selection of the CCD technology for the X-ray camera, solidification experiments with Al alloys and Al-zirconia composites in the prototype furnace, evaluation of specimens for the particle pushing flight experiment - PEPSI, measurements of emitted spectra from X-ray source, testing of the high resolution X-ray test targets, and the establishment of criteria for and selection of peripheral equipment. In addition to these tasks, two presentations were prepared in this period; one for the AIAA Microgravity Symposium and another for the Gordon Conference on Gravitational Effects in Pyisico-Chemical Systems.
X-ray induced optical reflectivity
Durbin, Stephen M.
The change in optical reflectivity induced by intense x-ray pulses can now be used to study ultrafast many body responses in solids in the femtosecond time domain. X-ray absorption creates photoelectrons and core level holes subsequently filled by Auger or fluorescence processes, and these excitations ultimately add conduction and valence band carriers that perturb optical reflectivity.Optical absorption associated with band filling and band gap narrowing is shown to explain the basic features found in recent measurements on an insulator (silicon nitride, Si3N4), a semiconductor(gallium arsenide,GaAs), and a metal (gold,Au), obtained with ?100 fs x-ray pulses at 500-2000 eV and probed with 800 nm laser pulses. In particular GaAs exhibits an abrupt drop in reflectivity, persisting only for a time comparable to the x-ray excitation pulse duration, consistent with prompt band gap narrowing.
The Need for X-Ray Spectroscopy
NASA Technical Reports Server (NTRS)
Winebarger, Amy R.; Cirtain, Jonathan; Kobayashi, Ken
For over four decades, X-ray, EUV, and UV spectral observations have been used to measure physical properties of the solar atmosphere. During this time, there has been substantial improvement in the spectral, spatial, and temporal resolution of the observations for the EUV and UV wavelength ranges. At wavelengths below 100 Angstroms, however, observations of the solar corona with simultaneous spatial and spectral resolution are limited, and not since the late 1970's have spatially resolved solar X-ray spectra been measured. The soft-X-ray wavelength range is dominated by emission lines formed at high temperatures and provides diagnostics unavailable in any other wavelength range. In this presentation, we will discuss the important science questions that can be answered using spatially and spectrally resolved X-ray spectra.
X-Ray Background Survey Spectrometer (XBSS)
NASA Technical Reports Server (NTRS)
Sanders, W. T. (Principal Investigator); Paulos, R. J.
The objective of this investigation was to perform a spectral survey of the low energy diffuse X-ray background using the X-ray Background Survey Spectrometer (XBSS) on board the Space Station Freedom (SSF). XBSS obtains spectra of the X-ray diffuse background in the 11-24 A and 44-84 A wavelength intervals over the entire sky with 15 deg spatial resolution. These X-rays are almost certainly from a very hot (10(exp 6) K) component of the interstellar medium that is contained in regions occupying a large fraction of the interstellar volume near the Sun. Astrophysical plasmas near 10(exp 6) K are rich in emission lines, and the relative strengths of these lines, besides providing information about the physical conditions of the emitting gas, also provide information about its history and heating mechanisms.
Understanding X-ray super-saturation
NASA Astrophysics Data System (ADS)
Hussain, Gaitee
X-ray emission is commonly used to measure magnetic activity in cool stars. While X-ray levels and magnetic activity levels rise with stellar rotation rate, X-ray luminosities actually decline or "super-saturate" in the most rapidly rotating stars. Conflicting theories have been used to explain this: e.g., magnetic dynamos are inhibited, surface fields are more confined or their heating is less efficient, or emission is reduced due to centrifugal stripping of the outer corona. We will test different explanations of super-saturation through a multi-wavelength study of the star, AP 139. By comparing rotational modulation in its X-ray lightcurves and temperatures with maps of surface activity we can learn if and how this phenomenon is related to changes in the star's surface fields.
X-Ray Methods to Estimate Breast Density Content in Breast Tissue
NASA Astrophysics Data System (ADS)
Maraghechi, Borna
This work focuses on analyzing x-ray methods to estimate the fat and fibroglandular contents in breast biopsies and in breasts. The knowledge of fat in the biopsies could aid in their wide-angle x-ray scatter analyses. A higher mammographic density (fibrous content) in breasts is an indicator of higher cancer risk. Simulations for 5 mm thick breast biopsies composed of fibrous, cancer, and fat and for 4.2 cm thick breast fat/fibrous phantoms were done. Data from experimental studies using plastic biopsies were analyzed. The 5 mm diameter 5 mm thick plastic samples consisted of layers of polycarbonate (lexan), polymethyl methacrylate (PMMA-lucite) and polyethylene (polyet). In terms of the total linear attenuation coefficients, lexan ? fibrous, lucite ? cancer and polyet ? fat. The detectors were of two types, photon counting (CdTe) and energy integrating (CCD). For biopsies, three photon counting methods were performed to estimate the fat (polyet) using simulation and experimental data, respectively. The two basis function method that assumed the biopsies were composed of two materials, fat and a 50:50 mixture of fibrous (lexan) and cancer (lucite) appears to be the most promising method. Discrepancies were observed between the results obtained via simulation and experiment. Potential causes are the spectrum and the attenuation coefficient values used for simulations. An energy integrating method was compared to the two basis function method using experimental and simulation data. A slight advantage was observed for photon counting whereas both detectors gave similar results for the 4.2 cm thick breast phantom simulations. The percentage of fibrous within a 9 cm diameter circular phantom of fibrous/fat tissue was estimated via a fan beam geometry simulation. Both methods yielded good results. Computed tomography (CT) images of the circular phantom were obtained using both detector types. The radon transforms were estimated via four energy integrating techniques and one photon counting technique. Contrast, signal to noise ratio (SNR) and pixel values between different regions of interest were analyzed. The two basis function method and two of the energy integrating methods (calibration, beam hardening correction) gave the highest and more linear curves for contrast and SNR.
Principles of X-ray Navigation
Hanson, John Eric; /SLAC
X-ray navigation is a new concept in satellite navigation in which orientation, position and time are measured by observing stellar emissions in x-ray wavelengths. X-ray navigation offers the opportunity for a single instrument to be used to measure these parameters autonomously. Furthermore, this concept is not limited to missions in close proximity to the earth. X-ray navigation can be used on a variety of missions from satellites in low earth orbit to spacecraft on interplanetary missions. In 1997 the Unconventional Stellar Aspect Experiment (USA) will be launched as part of the Advanced Research and Global Observation Satellite (ARGOS). USA will provide the first platform for real-time experimentation in the field of x-ray navigation and also serves as an excellent case study for the design and manufacturing of space qualified systems in small, autonomous groups. Current techniques for determining the orientation of a satellite rely on observations of the earth, sun and stars in infrared, visible or ultraviolet wavelengths. It is possible to use x-ray imaging devices to provide arcsecond level measurement of attitude based on star patterns in the x-ray sky. This technique is explored with a simple simulation. Collimated x-ray detectors can be used on spinning satellites to provide a cheap and reliable measure of orientation. This is demonstrated using observations of the Crab Pulsar taken by the high Energy Astronomy Observatory (HEAO-1) in 1977. A single instrument concept is shown to be effective, but dependent on an a priori estimate of the guide star intensity and thus susceptible to errors in that estimate. A star scanner based on a differential measurement from two x-ray detectors eliminates the need for an a priori estimate of the guide star intensity. A first order model and a second order model of the two star scanner concepts are considered. Many of the stars that emit in the x-ray regime are also x-ray pulsars with frequency stability approaching a part in 10{sup 9}. By observing these pulsations, a satellite can keep accurate time autonomously. They have demonstrated the acquisition and tracking of the Crab nebula pulsar by simulating the operation of a phase-locked loop.
Tsinghua Thomson scattering X-ray source
Chuanxiang Tang; Wenhui Huang; Renkai Li; Yingchao Du; Lixin Yan; Jiaru Shi; Qiang Du; Peicheng Yu; Huaibi Chen; Taibin Du; Cheng Cheng; Yuzheng Lin
We proposed the Tsinghua Thomson scattering X-ray (TTX) source as an ultra-fast, high flux source for advanced X-ray imaging studies and applications. A linac system, which consists of an S-band photocathode RF gun, a SLAC type 3m traveling wave tube and two X-band structures, generates ultra-short, high brightness electron pulses to scatter with tera-watt femto-second laser pulses. A compact low
A statistical X-ray QSOs classification
A. Coradini; F. Giovannelli; M. L. Polimene
A sample of 40 X-ray-emitting QSOs observed by the Einstein Observatory (Tananbaum et al., 1979) is characterized statistically using the G-mode method (Giovannelli et al., 1981) without a priori knowledge of taxonomic units. Parameters used in the classification (into nine classes forming two distinct clusters of four classes each with one intermediate class) include redshift, net counts, X-ray luminosity, and
NASA Technical Reports Server (NTRS)
Bulthuis, Ronald V.
X-ray imaging instrument adapted to continuous scanning. Modern version of fluoroscope enables rapid x-ray inspection of parts. Developed for detection of buckling in insulated ducts. Uses radiation from radioactive gadolinium or thallium source. Instrument weighs only 6 1/2 lb. Quickly scanned by hand along duct surface, providing real-time image. Based on Lixiscope, developed at Goddard Space Flight Center.
X-ray Spectroscopy of Inorganic Materials
P. S. Miedema
X-ray spectroscopies have been applied on different inorganic materials with a main focus on 3d-metal materials and iron compounds in particular. Different theoretical treatments of x-ray absorption spectroscopy (XAS) are compared with each other and with experimental data. XAS calculations have been performed for iron to study the XAS shapes of different spin states of iron as well as the
Next-Generation X-Ray Astronomy
NASA Astrophysics Data System (ADS)
White, Nicholas E.
This review of future timing capabilities in X-ray astronomy includes missions in implementation (astro-h, gems, srg and astrosat), those under study (currently nicer, athena and loft), and new technologies that may be the seeds for future missions, such as lobster-eye optics. Those missions and technologies will offer exciting new capabilities that will take X-ray Astronomy into a new generation of achievements.
N. M. Ceglio; D. G. Stearns; A. M. Hawryluk; T. M. Barbee; K. Danzmann; M. Kuehne; P. Mueller; B. Wende; M. B. Stearns; A. K. Petford-Long; C.-H. CHANG
We report progress in the development of multilayer components for use in multiple pass soft X-ray laser cavities operating in the 100A to 300A spectral range. Our work includes fabrication and characterization of multilayer components; simple resonant cavity design; damage threshold assessment for multilayers in the X-ray laser environment; and multipass cavity experiments for efficiency enhancement and transverse mode selection.
The high energy X-ray universe
Giacconi, Riccardo
Since its beginning in the early 1960s, the field of X-ray astronomy has exploded, experiencing a ten-billion-fold increase in sensitivity, which brought it on par with the most advanced facilities at all wavelengths. I will briefly describe the revolutionary first discoveries prior to the launch of the Chandra and XMM-Newton X-ray observatories, present some of the current achievements, and offer some thoughts about the future of this field. PMID:20404148