A method for analyzing a target analyte gas concentration using a photoacoustic spectroscopy cell comprising:    i) a modulatable light source which provides optical radiation at an absorption wavelength of a target analyte;    ii) a resonant acoustic chamber for containing said analyte;    iii) a microphone positioned within said chamber whereby the acoustic reactance of the microphone is substantially equal but opposite in value to the acoustic reactance of the chamber at a selected cell resonance frequency.

As semiconductor technology advances and device sizes shrink, the impact of contaminants in the gases used to fabricate these devices becomes increasingly important. Many specialty gases are used in the production of semiconductor devices. For example, a major source of contamination in the chip fabrication process is the presence in process gases of trace amounts, e.g., on the order of tens of parts per billion by volume (ppbv), of water. While ultra pure (water and other contaminant free) gases are sometimes available, chemical reactions, phase changes, and other effects often result in the presence of moisture in a gas supply line of a semiconductor fabrication system. These facts make it very attractive to have moisture sensors that are small, efficient, have rapid response times, and are inexpensive enough to be placed in multiple locations in the system. These locations include each line of the gas box and also immediately before the reactor of a semiconductor fabrication system. Currently available sensors do not meet all the aforementioned requirements.
The ambient atmosphere typically contains water vapor concentrations of up to, or even exceeding, approximately 1%. This is at least six orders of magnitude greater than the acceptable limits for most semiconductor process gases. As such, even very small leaks of ambient air into the gas distribution system may introduce significant moisture contamination. Furthermore, even well-dried gas lines can contribute moisture to an otherwise high-purity gas. After a gas distribution system is purged with an inert gas, some water molecules can remain in the lines due to strong binding to adsorption sites on metal and metal oxide surfaces. Subsequently, when polar gases such as HBr and HCl enter the feed gas lines, they tend to displace water molecules, which then enter the feed gas stream. Additionally, surface oxides within the gas distribution system can interact with corrosive gases to create water molecules by chemical reactions such as the following:Fe2O3+6HCl2FeCl3+3H2OSince even dry components within the distribution system can spontaneously create water, it seems clear that the semiconductor industry needs real time, in-line moisture monitors to protect wafer fabrication systems from moisture contamination.
Semiconductor fabs require as many as 50 gases to process a wafer. Table 1 lists some of the gases associated with different process steps. Contaminants in these gases can diminish yields and degrade chip reliability. Purity requirements for process gases will likely become even more strict as chip line widths continue to shrink. As indicated, one common contaminant is water vapor which can distort manufacturing processes and thereby compromise device performance. Process steps which are vulnerable to moisture contamination include epitaxial growth, sputtering, metal-organic vapor phase epitaxy, thermal etching, gas phase etching of tungsten films, plasma etching of silicon and polysilicon, and chemical vapor deposition of polysilicon, silicon dioxide, silicon nitride, and tungsten. The presence of water can accelerate or retard the chemical reactions which occur during deposition or etching, thereby altering the thickness and/or composition of critical layers. Moisture can create pitting, hazing, and stacking faults; cause resist patterns to fail; induce diodes and junctions to leak; and otherwise degrade the service lifetime of products which pass inspection and reach the marketplace.
TABLE 1Process Steps and Associated GasesProcess StepsGases (Inert Gases, Hydrides, and Corrosives)OxidationCarriersAr, N2ReactantsCl2, H2, HCl, O2PhotolithographyCarriersAr, N2,EtchingPlasma or ReactiveAr, BCl3, Cl2, CF2, CF4, C2F6,Ion EtchingHe, H2, N2, O2, C2F8, SiF4, SF6CarriersAr, H2, Ne, XeDiffusionCarriersAr, H2, N2, O2Dopant SourcesAsH3, BCl3, B2H6, PH3Chemical VaporOxidationCO2, N2, O2, H2SiCl2, SiH4DepositionDopingAsH3, B2H6, , PH3, SiH4NitrideN2O, SiCl4, NH3III–V LayersAsH3, H2, HCl, H2S, PH3Ion ImplantationAr, AsH3, BCl3, BF3, B11F3, Cl2, He, H2,H2S, N2, PH3, SiH4, P2F6, SiF4AnnealingAr, H2, N2MetallizationArBondingAr, H2, N2Crystal GrowthAr, He, H2EpitaxyCarriersAr, H2, N2Silicon SourcesSiH4, H2SiCl2, HSiCl3, SiCl4DopantsAsH3, B2H6, PH3EtchantHCl
Additionally, moisture will react with certain process gases, yielding acids which corrode gas handling equipment. For example, aqueous hydrochloric acid attacks iron and other constituents of stainless steel. As corrosion advances, pipes, valves, mass flow meters, mass flow controllers, and other components can fail, causing equipment downtime. Furthermore, corroded pipes release particles which enter the gas stream. Gas-phase nucleation by particles and flaking of particles from gas lines onto wafers can reduce yield. According to one report, the gas distribution system accounts for 68% of all contamination in CMOS processes. Moisture in arsine and phosphine lines may also contaminate the ultra-high-vacuum chambers used for doping wafers. Water molecules in the chamber can make it impossible to draw a sufficiently high vacuum, forcing engineers to shut down the chamber and subject it to an extended bake.
Manufacturers of LED's and VCSELs generally deposit three to five epitaxial layers by organometallic vapor phase epitaxy, using ultra-high-purity anhydrous ammonia as a process gas. Trace oxygen in the epitaxial layers can limit device performance. The photoluminescence of LED's and VCSELs depend strongly on the moisture content of the ammonia used during production and therefore to increase the efficiency, the amount of moisture needs to be accurately monitored during production.
Kermarrec and co-workers have studied the effect of moisture on SiGe devices. In their words, "A direct correlation between moisture impurity in process gases and atomic oxygen present in epitaxial SiGe layers was demonstrated, both qualitatively and quantitatively. The resulting incorporation of oxygen atoms can induce dislocations into the strained layers, which may degrade device performance and, subsequently, reliability." O. Kermarrec et. al., Solid State Technology, 45(3). Pp. 55-60, 2002.
Sensors for process gases in the semiconductor industry should advantageously have the following characteristics:    be sensitive enough to detect moisture or other contaminants in concentrations of <10 parts per billion by volume (ppbv),    be fast enough to react to changes in gas flows that may last less than 30 seconds,    be small enough (<1 ft3, or 0.029 m3) to fit among the gas lines and the surrounding areas,    be quick-drying enough to return the process tool that it monitors to productive use within an hour, and inexpensive enough (<$10,000) to be placed at multiple locations.Unlike the sensor design of the present invention, the prior art designs have been unable to fulfill all these requirements
Moisture sensors (monitors) are often referred to as "in-line" or "at-line". Generally, in-line refers to a monitor that is in the gas line such that the gas under test passes through the monitor without a need for tapping off the line. The term at-line is generally used for monitors that tap some flow off of the gas line. The flow that is tapped off is generally discarded. Both in-line and at-line monitors for semiconductor industry process gases should advantageously have the above-indicated characteristics, which are not available with current technologies. Since none of the technologies available today can satisfy all of these criteria and therefore do not meet the needs of fab operators, it is not surprising that wafer fabs rarely deploy in-line monitors. The present invention satisfies an unmet industry need by providing a system which meets all four requirements (sensitivity, speed, size, and price) and is suitable for both in-line and at-line sensors.
Of course, the detection of trace contaminants or other target analytes present in a liquid or solid matrix is also a matter of significance in a wide variety of industrial, medical, academic and defense contexts. Although the present invention will be discussed primarily in the context of analyte detection in a gaseous medium, it is to be understood that the unique photoacoustic apparatus and method of the present invention is suitable for the detection of target analytes present in a gaseous, liquid or solid matrix. Furthermore, although the present invention will be described primarily in the context of moisture detection, it should be recognized that it is applicable to the detection of essentially any fluid (i.e., gas or liquid) that is photoacoustically active and whose absorption peak or peaks coincide with the emission frequency of an available light source capable of supplying optical energy.
Photoacoustic Spectroscopy (PAS) studies optical events which through non-radiative transitions have become acoustic events. The molecules of any given compound absorb light at specific wavelengths characteristic of the compound and undergo quantized vibrational or rotational transitions. They gain kinetic energy in the form of heat, and collide with other neighboring molecules thereby creating a pressure wave. Since a pressure wave in a gaseous or liquid medium is sound, it can be detected by a microphone. As used in the present invention, the term "microphone" connotes any acoustic sensing mechanism capable of detecting a pressure wave or velocity in a gaseous or liquid medium. Examples include electric and diaphragm microphones and piezoelectric transducers. The sensitivity of a PAS instrument is determined primarily by: i) the efficiency with which the optical excitation produces a pressure wave in the fluid (i.e., gas or liquid) contained in an acoustic chamber, and ii) the efficiency with which the acoustic wave is converted into an electrical signal. In the simplest case these efficiencies can be multiplied to determine the total instrument efficiency. In the most general case the microphone contains moving parts which affect the acoustic impedance of the instrument so the total instrument efficiency can only be determined by including the interaction between the microphone and the acoustic chamber.
In order to further elucidate the photoacoustic effect it is useful to consider the physical steps that result in a photoacoustic signal. The photoacoustic effect in a photoacoustic chamber (often although not invariably in the form of a tube) can be divided into four sequential events: 1) absorption of incident optical radiation by a target analyte molecule; 2) heat release due to transformation of the absorbed light energy into molecular motion; 3) pressure wave generation due to heat induced expansion of the fluid present in the acoustic chamber; and 4) detection of the acoustic signal generated by the pressure wave. In the context of the present invention, it should be understood that the target analyte can be a gas or liquid which is: i) dispersed in a gas or liquid which fills the acoustic chamber, or ii) dispersed in a solid matrix which is contained within a gas filled acoustic chamber.
Alexander Graham Bell discovered the photoacoustic (Tyndall-Roentgen) effect in 1881. However, scientific and technological interest in the effect lay dormant for approximately 80 years in the absence of suitable light sources and microphones. In the 1960's, lasers stimulated researchers to explore using the photoacoustic effect for spectroscopic analysis. In 1968, Kerr and Atwood were able to detect low concentrations of pollutants in air by using lasers and phase-sensitive, lock-in acoustic detection techniques. (E. L. Kerr, and J. G. Atwood, "The laser illuminated absorptivity spectrophone: a method for measurement of weak absorptivity in gases at laser wavelengths," Applied Optics, No 7, p. 915-921, 1968Kreuzer detected methane in nitrogen in 1971, using an intensity-modulated He—Ne laser (L. B. Kreuzer, "Ultralow gas concentration infrared absorption spectroscopy," J. Applied Physics, Vol. 42, p. 2934-2943, 1971. See also: Aniko Veres, Zoltan Bozoki, Arpad Mohacsi, Miklos Szakall and Gabor Szabo; External Cavity Diode Laser Based Photoacoustic Detection of CO2 at 1.43 um: The Effect of Molecular Relaxation; Applied Spectroscopy, Vol. 57, No. 8, pp. 900-905, 2003. Per Ohlckers, Alain. M. Ferber, Vitaly K. Dmitriev and Grigory Kirpilenko; A Photoacoustic Gas Sensing Silicon Microsystem; Transducers 2001, Jun. 10-14, 2001. P. D. Goldan and Kito Goto; An acoustifcally resonant system for the detection of low-level infra-red absorption in atmospheric pollutants; J. Appl. Physics; Vol. 45; No. 10; pp. 4350-4355, October, 1974. J. -P. Besson, S. Schilt, L. Thevenaz; Mulit-gas Sensing Based on Photoacoustic Spectroscopy using Tunable Laser Diodes; Spectrochemica; Vol. 60; pp. 3449-3456; 2004. Lars-Goran Rosengren; Optimal Optoacoustic Detector Design; Applied Optics; Vol. 14; No. 8; pp. 1960-1976; August, 1975. M. Szakall, Z. Bozoki, M. Kraemer, N. Spelten, O. Moehler, and U. Schurath; Evaluation of a Photoacoustic Detector for Water Vapor Measurements under Simulated Tropospheric Conditions; Environ. Sci. Tech.; Vol. 35; No. 24; pp. 4881-4885; 2001. A. Miklos, P. Hess, Z. Bozoki; Application of Acoustic Resonators in Photoacoustic Trace Gas Analysis and Metrology; Rev. Sci. Instru., Vol. 72; No. 4; pp. 1937-1955; April 2001. M. Sigrist; Laser Generation of Acoustic Signals in Liquids and Gases; J. Appl. Phys.; Vol. 60; No. 7; pp. R83-R121; October 1986. M. Sigrist; Trace Gas Monitoring by Photoacoustic and Related Techniques; Rev. Sci. Instr.; Vol. 74; No. 1; pp. 486-490; January 2003. M. Nagale and M. Sigrist, Mobile Laser Spectrometer with Novel Resonant Multipass Photoacoustic Cell for Trace-Gas Sensing; Appl. Phys. B; Vol. 70; pp. 895-901; June 2005. S. L. Firebaugh; Miniaturization and Integration of Photoacoustic Detection; Ph.D. Thesis; MIT, May 2001.
As is apparent from the numerous above-cited references, there is a large body of work on both the theoretical fundamentals of photoacoustic spectroscopy, and also on the physical systems that have heretofore been used to carry out photoacoustic spectroscopy. Several companies sell PAS based detection systems, comprising either an incoherent or coherent light source, an acoustic cell, a microphone and means (usually a transducer) to convert a pressure to a voltage, and electronics to collect data and to digitize the output signal from the transducer. Researchers have utilized these systems to explore applications in environmental monitoring, life sciences, and medicine. Historically, the most sensitive systems employ large, high-power (>2 W) CO or CO2 lasers. Widely deployable systems, however, will require compact and inexpensive light sources.
In 1996, a group at the Hungarian Academy of Sciences reported using a photoacoustic cell situated inside the optical cavity of a diode laser to achieve a significant gain in detection efficiency compared to extracavity operation. (Z. Bozoki, et. al., Appl. Phys., B 63, 399 (1966). The same group later described a PAS system which supplied optical power with a DFB laser (M. Szakáll, Z. Bozôki, A. Mohâcsi, A. Varga, and G. Szabô, "Diode Laser Based Photoacoustic Water Vapor Detection System for Atmospheric Research," Applied Spectroscopy, Volume 58, Number 7, 792-798, 2004). This system reportedly was able to detect moisture at levels of about 250 ppbv and would therefore appear to have come within a factor of about 25 of the minimum required sensitivity for semiconductor gases, but did not meet the criteria for industrial use in terms of size or cost. This attempt at making a compact, inexpensive PAS systems highlights the state of the art of miniaturized PAS systems.
It is known that the configuration of the cell in which the gas is contained can influence the detection process. The first cells used to detect gaseous analytes were simple cylinders with windows at each end which were more or less transparent to the optical excitation beam. The optical signal entering the cell was modulated to induce a pressure wave at an acoustic resonance frequency of the cell and this pressure wave detected using a microphone affixed to the interior wall of the cell. This process can be optimized by analyzing the pressure variation within the cell structure that is caused by the optical excitation beam and adjusting the microphone placement to maximize the microphone output voltage or current for a given optical modulation frequency The prior art did not realize that the detection sensitivity can be maximized by causing the microphone to form a significant part of the resonant system as opposed to considering only the cell itself without a microphone. Specifically, I have found that the photoacoustic cell response can be optimized by allowing the microphone to be an integral part of the resonant acoustic cell as opposed to a passive monitor of the pressure wave developed in the acoustic cell.
Light sources may be modulated directly or externally. The light source modulation method is not a determining factor in this patent and many different schemes are known to those skilled in the art. Direct modulation means that the source power output or wavelength may be changed by directly changing the operating current or temperature of the source. External modulation means that a device outside of the light source is used to change the power or phase of the light source. External amplitude modulation is often achieved by a shutter and external phase modulation is often achieved by passing the light source through one of various electro-optic materials. The type of light source modulation is not essential to this patent, and the various methods of direct and external modulation are described in the literature and known to those skilled in the art.
The light source modulation frequency is set by the cell acoustic resonance frequency. The light source frequency is not a determining factor in this patent and any frequency may be used as constrained by the final product requirements considered by those skilled in the art. The light source modulation frequency is also affected by the detection scheme chosen (typically 1f or 2f). The selection of a scheme can depend on available lasers, target analytes, available power sources, or system size constraints. If external amplitude modulation is chosen the source modulation frequency will typically be equal to the acoustic resonance frequency. If wavelength source modulation is used then the acoustic resonance frequency will typically be twice the source modulation frequency. This is called 2f modulation and is described in the next paragraph. 2f modulation is part of the preferred embodiment of this invention but is not required for this invention.
A 2f modulation scheme, is described in Reid and Labrie, Second-Harmonic Detection with Tunable Diode Lasers—Comparison of Experiment and Theory, Applied Physics, #26, pp. 203-210, 1981, and has the advantage of rejecting many different sources of background noise. This scheme is typically realized by wavelength modulation of the optical source. As the optical source is swept back and forth across the absorption feature of the target analyte (with one complete cycle of the wavelength going shorter and longer and then back to ? over the feature wavelength) this causes the absorption feature to be encountered twice. The detector, (microphone) thus responds twice for every modulation cycle of the lightsource. This means that the desired microphone response is at twice the modulation frequency whereas any spurious signals created at the modulation frequency will be at the source frequency and thus easily rejected.
The acoustic resonance frequency of the photoacoustic cell is not a critical parameter in this patent. This parameter may be chosen to satisfy any number of system design constraints such as system size, external noise rejection, available microphones or even arbitrarily chosen. Anyone skilled in the art of engineering can either pick an acoustic resonance frequency based on system design constraints, or pick an arbitrary acoustic resonance frequency and design a PAS cell according to the constraints of this invention.
Equation (1) describes the sensitivity of a prior art cylindrical resonant photoacoustic cell, as shown in FIG. 1a, operating on the first longitudinal node, and suggests the issues facing the design engineer:
                              S          PAS                ∝                              P                                                                          α                                                                          l                                                                                Q                              a                                                                                c                                                          V                        ω                                              Equation                                                            (          1          )                    In Equation (1) SPAS is the sensitivity of the PAS system, P is the optical power in the acoustic cavity, α is the absorption coefficient of the target analyte gas, l is the absorption path length, Qac is the quality factor of the acoustic cavity, V is the volume of the acoustic cavity, and ω is the resonant frequency of the cell. Equation (1) indicates that sensitivity is proportional to l (the path length) divided by V (the cavity volume). For a cylindrical resonant cavity, V divided by l is the cross sectional area of the cavity. Equation (1) suggests that theoretically a cylindrical cavity with a vanishingly small diameter would have infinite sensitivity. For the purposes of this patent, cavity will refer to the main acoustic resonator and cell will refer to the cavity with the microphone, and possible connecting tubes, attached. In practice, the applicability of Equation (1) to very small diameter resonant acoustic cells is limited by turbulence and boundary layer effects near the cell walls for very small diameter resonator tubes. I have found that a suitable diameter for the resonant cavity of a PAS in accordance with my invention will range from about 0.1 mm to about 20 mm, preferably from about 2 mm to 10 mm, most preferably 1 to 4 mm.
Methods and systems for increasing the sensitivity of photoacoustic spectroscopy cells, while simultaneously reducing their size and the cost, are essential if widespread industrial use is to be realized. Photoacoustic systems for industrial use will preferably utilize small and inexpensive light sources, such as the semiconductor diode lasers heretofore developed for telecommunications use. Such lasers are small, relatively inexpensive, and convert electrical energy into optical energy with high efficiency. Traditional PAS cell designs are discussed in detail in books such as "Optoacoustic Spectroscopy and Detection" by Pao, Academic Press, 1977. Traditional photoacoustic sensor cells use microphones as a sensing device for the pressure waves in the acoustic cavity. All these prior art cell designs are predicated on the assumption that the microphone does not significantly influence the cell sensitivity or cell resonance frequency. I have found that by using the microphone impedance as part of the total acoustic network (i.e., cell plus microphone) one can substantially reduce the cell size while maintaining or increasing the detection sensitivity. In general, it is very helpful to utilize the analogies between electrical and acoustical systems, as the general tools in existence for solving electrical circuit problems are quite mature. This analogy will be described in great detail later, but it will be helpful to know now that a volume displacement or acoustical compliance is analogous to a capacitance, while an acoustically short tube can act as an acoustic resistance and inertance which is represented electrically by resistance and inductance respectively. With these definitions in mind, reference to acoustic quantities in electrical engineering terminology should have specific meaning.
The microphone impedance may be incorporated into (combined with) the PAS cell impedance in a number of ways. One approach is to operate the PAS cell at a low frequency using tubes of a diameter much less than their length which open into buffer regions of much larger diameter or even open air, as shown in FIGS. 2 and 4. This results in the PAS cell acting like an equivalent acoustic inductance. For a resonance to also occur there must also be an equivalent acoustic capacitance to complete the energy exchange of a resonator. I have discovered that a resonant cell can be achieved by placing the microphone in the PAS cell and using the back-volume of a microphone to act as an equivalent acoustic capacitance.
PAS cells in accordance with the present invention use resonant acoustic cavities. Resonant cavities can be realized in different forms, either lumped (commonly referred to as Helmholtz resonators), or distributed. The distinction between lumped and distributed cavities can be described as follows. As the acoustic cavity resonant frequency increases the acoustic wavelength of the chamber decreases and the dimensions of the structure will approach a substantial fraction (e.g. an eighth or more) of an acoustic wavelength, causing the pressure and volume velocity to show significant changes along the axis of the chamber. This pressure and volume velocity variation with distance along the axis of the chamber means that the inductive and capacitive attributes can no longer be considered as lumped in certain regions of the chamber but must now be considered as distributed along the chamber (See e.g., "Theoretical Acoustics", Morse and Ingard, Princeton University Press, 1968). PAS cell geometries in accordance with the present invention can have many shapes. A preferred embodiment of my invention is a tube between two optical windows with auxiliary tubes branching off near the optical windows. The branch tubes in this preferred embodiment end in buffer chambers of larger diameter connected to the analyte containing fluid inlet and outlet.
Helmholtz (or lumped for the purposes of this document) resonators are preferred for the practice of the present invention in that they permit a reduction in the size of the resonator chamber because, unlike distributed resonators, they do not require dimensions which approach that of the acoustic wavelength. Reducing the size of a PAS instrument is desirable for a variety of reasons including reduced cost and weight. The dimensions of the various elements of an acoustic system can be small in comparison with the wavelength of the generated sound and, when this is true, the motion of the fluid medium (usually a gas) in the system is analogous to that of a mechanical system having lumped mechanical elements of mass, stiffness and resistance. A Helmholtz resonator can be realized in a variety of configurations, two of which are shown in FIGS. 1a) and 1b). FIG. 1a) shows a Helmholtz resonator with one end open to the gas (or other fluid) containing the target analyte. The fluid in the large cavity acts as a spring, and the gas in the narrow tube acts as a mass because of the relative cross-sectional areas. The Helmholtz resonator shown in FIG. 1a), consists of a rigid enclosure of volume Vc, communicating with the external medium through a small opening of area S and length lm. The gas in the opening is considered to move as a unit and provides the mass element of the system, the pressure of the gas within the acoustic cell changes as it is alternately compressed and expanded by the influx and efflux of gas through the opening and thus provides the stiffness element. At the opening, moreover, there is radiation of sound into the surrounding medium which leads to the dissipation of acoustic energy and thus provides one source of frictional loss.
As mentioned before, acoustic systems can be analogized to electrical systems and quantitatively solved. In an analogous electrical system the motion of the fluid medium is equivalent to the behavior of current in an electric circuit having elements of inductance, capacitance, and resistance. The electrical analogue of the pressure difference across an acoustic element is the voltage across a component of an electric circuit. The acoustic analogue of current at some point in the circuit is equivalent to the volume velocity of the fluid in the acoustic element. The latter quantity is defined in terms of the rate of volume displacement of fluid in the acoustic element.
The analogy between acoustic and electrical systems may be advantageously carried further by again considering FIG. 1a) and defining the acoustic inertance M of a cylindrical acoustic element as:
                    M        =                  m                      S            2                                              Equation                                                            (          2          )                    where m is the mass of the element and S is the cross sectional area of the mass in the plane through which the mass moves. Typically an acoustic mass is related to a constriction, orifice, or column of air with an area, S, and length, lm. An application of this definition to a Helmholtz resonator in which the mass is a cylindrical volume of gas, Vm, gives:
                    M        =                                                            ρ                                V                            m                                      S              2                                =                                                    ρ                                                                                l                  m                                                S                                            S                2                                      =                                          ρ                                                                                l                  m                                            S                                                          Equation                                                            (          3          )                    where ρ is the density of the gas. Acoustic inertance is analogous to electrical inductance and has the dimensions of kg/m4 in the MKS system of units.
The acoustic compliance C of an acoustic element is defined as the volume displacement that is produced by the application of unit pressure. It is the analogue of electrical capacitance, (the charge appearing on a capacitor per unit of applied voltage). For an acoustic element having an enclosed volume Vc, such as in the Helmholtz resonator of FIG. 1a), this definition leads to:
                    C        =                              V            c                                ρ                                                                                c              2                                                          Equation                                                            (          4          )                    where lower case c is the speed of sound in the fluid, ρ is the density of the fluid (normally a gas), and Vc is the volume of the acoustic cavity. The units of acoustic compliance are m4 sec2/kg.
An element or characteristic of an acoustic system that leads to the dissipation of energy is analogous to electrical resistance. For example, a major portion of the acoustic resistance R of a Helmholtz resonator can result from the radiation of sound energy and is given by R=ρ c k2/2π, where k is 2π divided by the acoustic wavelength, It is also possible to derive expressions for the additional acoustic resistance associated with viscous forces in the fluid medium.
Helmholtz resonators are schematically represented in FIGS. 1a) and 1b). However, it should be understood that these acoustic systems may also be represented schematically by the circuit of the analogous electrical systems, i.e., FIGS. 3a) and 3b) which correspond to 1a) and 1b), respectively. In general, when it is possible to replace an acoustic system by the schematic circuit of an analogous electrical system, known solutions of the latter may be used to analyze the former. The analogies just described are those most commonly used in acoustics. However, another system of analogies known as the mobility system is sometimes also advantageously used. In the mobility system acoustic mobility, defined as the ratio of volume velocity across, to pressure through, the acoustic system is analogous to electrical impedance, volume velocity to voltage, pressure to current, inertance to capacitance, compliance to inductance and the reciprocal of the acoustic resistance to electrical resistance.
A known embodiment for a closed PAS cell is a 'dumbbell' Helmholtz resonator as shown in FIG. 1b). In FIG. 1b) the relatively large gas volumes on each end of the dumbbell act as springs and the central narrow tube acts as a mass which resonates with the springs. Typically in prior art designs a light source excites the gas in one of the tube ends and a microphone is located in the opposite end. Because PAS cell sensitivity for most configurations is inversely proportional to volume, the large gas volumes in the two ends of the dumbbell tend to limit cell sensitivity.
This invention is substantially independent of the optical source power. Light sources for my invention are preferably, but not limited to, coherent, wavelength (frequency) modulatable continuous wave lasers. Alternative sources may be incoherent, or pulsed lasers and directly or indirectly modulated. Likewise, although not preferred, the light source may be energy modulated. Collimated LED sources are also suitable for the practice of my invention. Sources of a wide power range are suitable. Preferably the power will range from about microwatts up to hundreds of milliwatts.
Acoustic cells fall within the scope of this invention if the cavity impedance at the interface to the microphone has an absolute impedance magnitude within a factor of three (i.e., ⅓ to 3 times that) of the microphone impedance magnitude and of opposite reactance to the microphone reactance. A preferred embodiment is an acoustic cylinder of diameter between about 1 and 4 mm with a length of approximately 40 to 100 mm between the optical windows. My invention also applies to PAS operation with liquid or solid matrixes. Examples of PAS operation using prior art cell designs with materials other than gases can be found in J. Pelzl, K. Klein, and O. Nordhaus, "Extended Helmholtz Resonator in Low-Temperature Photoacoustic Spectroscopy", Applied Optics, Vol. 21, No. 1, January 1982, pp. 94-99
My invention is directed to a photoacoustic cell wherein the acoustic impedances of both the acoustic sensor (i.e., the microphone) and the PAS chamber significantly interact. Since impedance equals pressure divided by volume velocity, by designing the cell and choosing the sensor so that the acoustic impedances of the chamber and the sensor are of substantially the same order of magnitude they will significantly interact. This permits a significant reduction in the acoustic chamber size and thereby significantly increases the sensitivity of the PAS cell. I have found that the impedance of the microphone should range from about one-third (⅓) to about three (3) times the impedance of the resonant chamber. I have discovered that use of the microphone as part of the resonant structure, e.g., as shown in FIG. 6, is a highly effective way of minimizing chamber volume.
The interaction between the high frequency modes and the microphone will depend on the relative impedances of the tube and the microphone. However, I have found that if the tube (acoustic chamber) dimensions are chosen correctly a mode will occur which is significantly lower in frequency than the first half-wavelength mode. For the purposes of this patent the tube dimensions are chosen so that its acoustic impedance is substantially equal in magnitude to (i.e., ⅓ to 3×) the microphone acoustic impedance at the desired resonance frequency. If the microphone impedance is capacitive at the desired resonance frequency then the chamber acoustic impedance must be inductive in order for it to resonate with the microphone impedance. This lowest order mode uses the back volume of the microphone as a spring and the gas in the tube as a mass. The tube length should be maximized for the greatest optical power absorption. Suitable lengths will range from about 20 mm to 200 mm, especially 40 mm to 100 mm. However, the tube diameter and length are ultimately determined by the requirement to have the cavity reactance substantially match the microphone reactance. The resulting resonant mode can correctly be called a Helmholtz resonance because it depends on the lumped properties of the gas mass in the tube and the spring constant of the microphone back volume. Because this realization permits a significant reduction in the PAS chamber volume it tends to maximize sensitivity as shown by Equation 1. Although larger chamber volumes are suitable for the practice of my invention, I have found that excellent sensitivity can be achieved with small cavity volumes in the range of from about 0.1 cc to 1.0 cc. For example, by using the compliance from the back-volume in a microphone as the equivalent spring in a resonant cavity the Vc section in FIG. 1a can be replaced with a microphone, thus permitting greatly reducing the size of the acoustic resonator chamber. This is because the diaphragm of a microphone combines with the volume of air behind the microphone (i.e., the "back-volume") to create an equivalent acoustic capacitance equal to a much larger volume chamber containing air alone.

System and method for gas analysis using photoacoustic spectroscopy


A method for fabricating a microelectronic structure includes the steps of forming a semiconductor island on a substrate and forming a filler material on the substrate and surrounding the semiconductor island. The semiconductor island includes a first semiconductor material and has a planar island surface opposite the substrate. The filler material includes a second semiconductor material and has a planar single crystal surface adjacent the planar island surface opposite the substrate so that the planar island surface and the planar single crystal surface together define a smooth planar surface. The first semiconductor material can be diamond, and the second semiconductor material can be silicon. In addition, a microelectronic circuit can be formed on the filler material.

Diamond is a preferred material for microelectronic devices because it has semiconductor properties that are superior to conventional semiconductor materials, such as silicon, germanium or gallium arsenide. Diamond provides a higher energy bandgap, a higher breakdown voltage, and a higher saturation velocity than these traditional semiconductor materials.
These properties of diamond yield a substantial increase in projected cutoff frequency and maximum operating voltage compared to devices fabricated using more conventional semiconductor materials. For example, silicon is typically not used at temperatures higher than about 200.degree. C. and gallium arsenide is not typically used above 300.degree. C. These temperature limitations are caused, in part, because of the relatively low energy band gaps for silicon (1.12 eV at ambient temperature) and gallium arsenide (1.42 eV at ambient temperature). Diamond, in contrast, has a relatively high band gap of 5.47 eV at ambient temperature, and is thermally stable up to about 1400.degree. C. in a vacuum.
Diamond also has the highest thermal conductivity of any solid at room temperature and exhibits good thermal conductivity over a wide temperature range. The high thermal conductivity of diamond may be advantageously used to remove waste heat from an integrated circuit, particularly as integration densities increase. In addition, diamond has a smaller neutron cross-section which reduces its degradation in radioactive environments, that is, diamond is a "radiation-hard" material. Diamond is also relatively chemically inert, optically transparent, and mechanically hard. Accordingly, diamond can be used advantageously in optical applications, and its mechanical hardness means that it is robust and can be used as an extremely effective abrasive agent. These mechanical properties also produce excellent acoustic characteristics.
Because of the advantages of diamond as a material for microelectronic devices, there is at present an interest in the growth and use of diamond for devices which can be used in environments which are subjected to high temperatures, radiation, and/or corrosive agents. For example, there is an interest in the use of diamond for sensors, thermal management devices, and electron beam devices such as field emitters and electron-activated switches. There is also an interest in the use of diamond for Surface Acoustic Wave ("SAW") devices because of the relatively high velocity of surface acoustic waves through diamond. SAW devices including diamond layers are discussed in U.S. Pat. Nos. 5,329,208, 5,355,568, and 4,952,832, all to Imai et al.
Unfortunately, the fabrication of a single crystal diamond film is typically carried out by homoepitaxial deposition of a diamond film on a single crystal diamond substrate. Such a single crystal diamond substrate is relatively expensive. In addition, large single crystal substrates may not be available for many applications.
A continuous layer of diamond, however, may not be suited for the large scale production of diamond devices or structures because a wafer with a continuous diamond layer may be difficult to cut into individual die. The ability to efficiently cut the production wafer into individual die is important because economies of scale dictate that many devices be fabricated simultaneously on a single wafer and then cut apart after fabrication. While substrates made from conventional materials such as silicon can be cut using a mechanical saw, a substrate including a diamond layer may require a more complicated cutting tool such as a laser because of the extreme hardness of diamond. Lasers, however, may be relatively expensive, and may induce micro cracks or other damage in the diamond. The use of lasers may also cause adhesion problems as a result of localized heating and thermal expansion, formation of non-diamond phases along the edges of cuts, and ablation of carbon residue onto devices.
A proposed microelectronic device having one or more semiconductor devices formed on a single crystal substrate, such as diamond, is described in U.S. Pat. No. 5,006,914 entitled "Single Crystal Diamond Substrate Articles and Semiconducting Device Comprising Same" to Beetz, Jr. et al. This patent discloses a microelectronic structure including a single crystal diamond substrate which is etched to form an array of spaced apart posts of single crystal diamond. On each post is grown a semiconducting layer of single crystal diamond to serve as an active channel region of a respective semiconductor device. Unfortunately, the use of a large single crystal diamond substrate as the starting point for the fabrication of the Beetz structure is relatively expensive. In addition, the diamond substrate may be difficult to cut into individual die.
Another microelectronic structure is described in U.S. Pat. No. 5,420,443 entitled "Microelectronic Structure Having An Array Of Diamond Structures On A Nondiamond Substrate And Associated Fabrication Methods" to Dreifus et al. The '443 patent is assigned to the assignee of the present invention, and it represents a significant advance in the state of the art. The '443 patent and the present invention also share common inventors.
The microelectronic structure of the '443 patent includes a single crystal non-diamond substrate, and a plurality of laterally spaced apart diamond structures are formed on the substrate extending outwardly therefrom. An interfacial carbide layer is preferably formed between the plurality of diamond structures and the non-diamond substrate, and the diamond structures are substantially oriented with respect to the non-diamond substrate. The diamond structures preferably have a substantially flat outermost face having a (100)-orientation to thereby provide a relatively large usable area in contrast to other crystalline orientations. The embodiment of the method of this patent provides nucleation of an array of diamond structures, each approaching single crystal quality without scratching or abrading the surface of the substrate.
Still another microelectronic structure is described in U.S. Pat. No. 5,300,188 entitled "Process For Making Substantially Smooth Diamond" to Tessmer et al. The '188 patent is also assigned to the assignee of the present invention, and it also represents a significant advance in the state of the art. The '188 patent and the present invention also share common inventors.
The '188 patent discusses a process for making a diamond layer having a substantially smooth upper surface and a predetermined thickness on a substrate. The process includes depositing a patterned polish stopping layer on a substrate to a predetermined thickness while leaving predetermined portions of the substrate exposed. In particular, the polish stopping layer is preferably a layer of a material such as various metals, polysilicon, silicon nitride, silicon oxide or other suitable materials capable of substantially stopping the consumption of diamond. A diamond layer is then deposited on the polish stopping layer and on the predetermined portions of the substrate left exposed.
Notwithstanding the above mentioned references, there continues to exist a need in the art for improved methods for forming diamond structures which can be used in the fabrication of microelectronic devices. There also exists a need in the art for economical methods for forming diamond structures which can be subsequently processed using conventional microfabrication techniques.

Methods for fabricating microelectronic structures including semiconductor islands


The present invention relates to developing an optimally efficient arginine-histidine-cysteine based peptide comprising nanocomplex that can deliver biomolecules across varied cell lines without any oxidative procedure through formation of monodisperse nanoparticles with sizes ranging between 50 and 110 nm.

The knowledge about the human genome in the last decade has helped in our understanding of the causes and molecular mechanisms for manifestation of various diseases. It is a well-accepted fact that the treatment for several monogenic and acquired genetic disorders as well as complex diseases like cancer can be fully or partially achieved by different types of gene therapy approaches [Rubanyi G M, 2001; Howard K A, 2009; Petros R A et. al., 2010]. Adopting such approaches is limited by the availability of safe and efficient vectors which can deliver the desired nucleic acid for gene expression/suppression to affected cells/tissues in the body. Viral gene delivery systems have been largely explored and account for more than 70% of clinical trials but their practical applicability to the clinics is still questionable due the associated risks like insertional mutagenesis and immune activation [Mark A K et. al., 2003]. Lipid and polymer based non-viral vectors provide a safer alternative and can also carry large cargo molecules unlike viral vectors but are of limited use because of their inability to overcome all the barriers encountered during in vivo delivery of nucleic acids and long term toxicity and biocompatibility issues. Additionally their synthesis demands specialized expertise and can often result in limited product yield posing economic constraints [Mintzer M A et. al., 2009; Remaut K et. al., 2007].
A more recent rational approach is the integration of different non-viral vectors such that they can complement each other's functions and systematically cross the hurdles encountered during in vivo gene delivery. Peptides are the best choice in this regard since different peptides possess the inherent ability to cross various cellular barriers like plasma, endosomal and nuclear membranes [Remaut K et. al., 2007; Mintzer M A et. al., 2009]. Peptides can also package different forms and sizes of nucleic acids to form nanocomplexes, and serve as cellular targeting ligands. Other advantages such as ease of synthesis and chemical modifications, relatively low toxicity and immunogenicity make peptides an attractive class of non-viral nucleic acid delivery agents [Vazquez E et. al., 2008; Martin M E et. al., 2007; Morris M C et. al., 2000; Hart S L et. al., 2010; Mann A et. al., 2008]. Peptides have been described in the literature for delivery of biomolecules like DNA and siRNA. Of these, lysine and arginine-rich peptides are the most promising vectors for plasmid DNA delivery since they can efficiently condense DNA and form nanocomplexes to prevent enzymatic degradation inside the cell [Mann A et. al., 2007]. In addition, arginine peptide show strong cellular uptake [Biessen E A L et. al., 2004; Wang S et. al., 2008; Harashima H et. al., 2009; Kim Y H et. al., 2009]. Arginine homopeptides possess better DNA condensation and release balance than their cognate lysine variants and thus are more efficient. However, the efficiency of delivery of a large cargo like plasmid DNA in the form of a nanocomplex by lysine and arginine homopeptides is rather low because of their inability to overcome the endosomal barrier effectively. Modification of lysine peptides in these nanocomplexes with histidines in linear as well as branched form have been shown to add endosomal escape property to the DNA condensing system [Kichler et. al., 2007]. However, such systems involve complicated design and synthesis steps and are not very efficient.
There is a need to design nanocomplexes containing cationic peptide which are able to overcome all the barriers for intracellular entry by showing high cellular uptake, efficient endosomal escape and high transfection efficiency with low toxicity.
In the present work we have explored various arginine-histidine-cysteine combinations and have developed nanocomplexes containing two novel cationic peptides with combinations of 9 arginine residues, 7 histidine residues and 2 cysteine residues at both ends that can efficiently overcome endosomal barrier but retain their DNA-condensation and release balance. Arginines have been used as condensing moieties, histidines are involved in efficient endosomal escape and the addition of cysteines further enhances the DNA condensation and release balance possibly through formation of reducible cross-linkages. These nanocomplexes show remarkable efficiency of plasmid DNA delivery comparable to commercially available transfection reagents in various cell lines including the ones which are tough to transfect. These particular nanocomplexes comprising linear arginine-histidine-cysteine sequences of short length (as described in the sequence listings) with high DNA delivery efficiency and low toxicity are completely unique.
Lysine/Arginine-histidine-cysteine nanocomplex systems listed in the literature are either (a) in the form of reducible polycations (RPCs) where the peptide has been polymerized before making a nanocomplex with the DNA or (b) the peptide-DNA nanocomplex is oxidized [Wang S et. al., 2008; Kim Y H et. al., 2009; Kim Y H et. al., 2010]. Such oxidation steps are not required in our nanocomplex system. This is an obvious advantage of our system over existing ones.

Nanocomplex containing cationic peptide for biomolecule delivery

Council of Scientific and Industrial Research


A connector between a first object having a first coefficient of thermal expansion and a second object having a second coefficient of thermal expansion has a slot attaching to the second object. The slot formed by an inner shell having a slot shape and a first portion that blends into an outer surface of the second object, the slot having an enclosed portion facing forward and an aft portion that is open.

Turbofans are a type of gas turbine engine commonly used in aircraft, such as jets. The turbofan generally includes high and low pressure compressors, high and low pressure turbines, high and low speed spool shafts, a fan, and a combustor. The high-pressure compressor (HPC) is connected to the high-pressure turbine (HPT) by the high speed spool rotatable shaft, and together act as a high-pressure system. Likewise, the low-pressure compressor (LPC) is connected to the low-pressure turbine (LPT) by the low speed spool rotatable shaft, and together act as a low-pressure system. The low speed spool shaft is housed within the high speed spool shaft and is connected to the fan such that the HPC, HPT, LPC, LPT, and high and low spool shafts are coaxially aligned.
Air is drawn into the gas turbine engine by the fan and/or the LPC. The HPC further increases the pressure of the air drawn into the system. The high-pressure air then enters the combustor, which burns fuel and emits exhaust gas. The exhaust gas flows from the combustor into the HPT where it rotates the high spool shaft to drive the HPC. After the HPT, the exhaust gas is exhausted to the LPT. The LPT uses the exhaust gas to turn the low spool shaft, which powers the LPC and the fan to continually bring air into the system. Air brought in by the fan bypasses the LPC and HPC, and acts to increase the engine's thrust, driving the jet forward.
In order to support the high and low pressure systems, bearings are located within the gas turbine engine to help distribute the load created by the high and low pressure systems. The bearings are connected to an engine casing that houses a mid-turbine frame located between the HPT and the LPT by bearing support structures. The bearing support structures can be, for example, bearing cones or struts. The load from the bearing support structures are transferred to the engine casing through the mid-turbine frame.

Pin connector for ceramic matrix composite turbine frame


A method of forming a field effect transistor creates shallower and sharper junctions, while maximizing dopant activation in processes that are consistent with current manufacturing techniques. More specifically, the invention increases the oxygen content of the top surface of a silicon substrate. The top surface of the silicon substrate is preferably cleaned before increasing the oxygen content of the top surface of the silicon substrate. The oxygen content of the top surface of the silicon substrate is higher than other portions of the silicon substrate, but below an amount that would prevent epitaxial growth. This allows the invention to epitaxially grow a silicon layer on the top surface of the silicon substrate. Further, the increased oxygen content substantially limits dopants within the epitaxial silicon layer from moving into the silicon substrate.

1. Field of the Invention
The present invention generally relates to forming field effect transistors and more specifically to the creation of shallower and sharper junctions, while maximizing dopant activation in processes that increase the oxygen content of the top surface of a silicon substrate before epitaxially growing a silicon layer on the silicon substrate, where the increased oxygen content substantially limits dopants within the epitaxial silicon layer from moving into the silicon substrate.
2. Description of the Related Art
As devices are scaled to smaller and smaller dimensions, shallower and sharper junctions are needed in transistors to control short channel effects and series resistance. The ability to reduce the oxide thickness (scale the oxide) is becoming more difficult in field effect transistor (FETs) and other similar integrated circuit design technologies. As it becomes more difficult to scale the oxide, it becomes more important to reduce the junction depth and increase junction sharpness. However, it is becoming more difficult to obtain shallower and sharper junctions with ion implantation and rapid thermal annealing as the devices become smaller. Therefore, there is a need for new methodologies and structures that create shallower and sharper junctions while maximizing dopant activation in processes that are consistent with current manufacturing techniques.

Ultra shallow junction formation by epitaxial interface limited diffusion

International Business Machines Corporation


Systems and methods for adaptively scanning for one or more beacon devices based at least in part on user activity are provided. More particularly, a user device can scan for one or more beacon devices at a first scan rate. The user device can detect a trigger event based at least in part on data indicative of an activity level, such as data indicative of a status of a display, data determined from one or more motion sensors, a number of beacon devices detected by the mobile device during a time period, data indicative of prior interactions with beacon device information, or data indicative of a charging status of a battery associated with the mobile device. The trigger event can signify a change in an activity level associated with the user device. Responsive to the trigger event, the user device can adjust the scan rate from the first scan rate to a second scan rate.

In recent years, location based functionality associated with mobile computing devices has become increasingly popular. Location based functionality can allow a user device, such as a smart phone, tablet or wearable computing device, to receive information and to perform actions associated with the information. Such location based functionality can be implemented, for instance, through the use of beacon devices. Beacon devices are a recent technology that can be used, for instance, in determining proximity and location. A beacon device is a small, low cost, self-contained device that can periodically provide (e.g. broadcast using a short range wireless communication technology) information. A user device can receive the information and use the knowledge of the identity of the beacon device and proximity to the beacon device for various purposes, including communication, asset tracking, retail identification, safety, localization, etc.

Adaptive scanning based on user activity


A fort includes a defense, a top cover, and a plurality of shooting windows. The top cover is mounted on top of the defense. The top cover includes an inverted bowl-like top wall with an opening. The top cover further includes a peripheral wall extending along a periphery of the top wall. The peripheral wall includes a plurality of engaging holes. Each shooting window includes a plurality of engaging holes. A plurality of fasteners are extended through the engaging holes of each shooting window and the engaging holes of the top cover, thereby releasably mounting the shooting windows to the peripheral wall of the top cover. A safe fort that can be assembled/dismantled easily and rapidly is thus provided.

1. Field of the Invention
The present invention relates to a fort. In particular, the present invention relates to a fort that can be assembled or dismantled easily.
2. Description of the Related Art
A conventional fort in a battlefield is constructed by a wall comprised of stacked sandbags or a ditch. Such a fort lacks protection in top. As a result, the soldiers in the fort are liable to be injured or even killed by grenades or fractures of cannon balls from top.


A cover opening and closing apparatus of an electronic appliance is provided. The apparatus includes a body comprising a container-shaped housing with an open side configured to insert and remove at least one electronic component, a cover configured to open and close an opening of the housing, and a moving hinge hinged to the cover, received in the body, and movable. When the cover rotates over a threshold angle, the cover rotates on a rotation axis being a protrusion contacting the body and a hinge connector between the cover away from the rotation axis and the moving hinge moves out of the body.

In accordance with advances in electronic communication industries, electronic appliances such as a cellular phone, a digital organizer, a personal digital assistant, a digital camera, and an electric shaver have become widely used. Such an electronic appliance includes a battery as a power source. In some electronic appliances, it is necessary to include a separate a case to exchange the battery. Most of the electronic appliances include a battery cover used to allow the battery's insertion and removal from the case.
Accordingly, an apparatus and method to increase an opening angle of a cover is required.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.

Cover opening and closing apparatus for electronic appliances


An improved portable handlamp has a fluorescent lamp mounted in a lens assembly. A flexible elastomer handle mounted to the base of the lens assembly provides a cavity for receiving a ballast in an interference fit. The ballast is connected to the lamp holder by a bracket which also serve to mount the actuating switch in a manner such that these components form a frame permitting the user to grasp the handle and maneuver the handlamp.

Electrical handlamps using incandescent lamps have been known for decades. These lamps have certain disadvantages in that they tend to become very hot during continued use, and most commercially available incandescent lamps are not well-suited to the rugged conditions of use of most handlamps, particularly those used in industrial and commercial applications. If a handlamp with an incandescent lamp is dropped, almost invariably the filament will break and the lamp must be replaced.
Fluorescent handlamps are also known. In one commercial fluorescent handlamp, the ballast is incorporated directly into the electrical power cord which feeds the handlamp, so that there is a longer section of cord between the ballast and the handlamp itself. A shorter section of electrical cord extends between the ballast and the outlet receptacle to which the plug is connected for use.
Although this device provides the advantages of greater efficiency and less heat build up than with incandescent lamps, it is somewhat cumbersome in that the ballast must be dragged around the floor. Further, the ballast, which is not light, must be supported. This limits portability and maneuverability. Finally, this system is difficult to service in the field if it is required to replace the ballast or other component.
There has also been a handlamp in which a ballast is included directly in the handlamp itself. This is an explosion-proof handlamp in which the handle of the lamp is a metal casing; and the ballast is incorporated into the metal handle and securely embedded in a potting compound within the handle. This explosion-proof construction is prohibitively expensive for ordinary commercial and industrial usage, and it is quite heavy, and, thus, not easily maneuvered or hung from a support.
The present invention overcomes these disadvantages and provides a simple and reliable handlamp, yet one which is economical to manufacture and easily serviced in the field without the need for special tools.


At a front end of the lateral arm of a surgical microscope apparatus, the apparatus has an intake port. A band is tied around the front end of the lateral arm so that a drape is drawn only to a surgical microscope. Drawing the drape to the surgical microscope results in clearing the field of vision of a surgeon. Part of the drape around the lateral arm and a longitudinal arm is not drawn, to cause no hindrance in operability of the surgical microscope. The lateral arm and the like are hollow to form an inner ventilating path without separately preparing ventilating tubes or the like for ventilation.

1. Field of the Invention
The present invention relates to a surgical microscope apparatus used with a drape that covers the apparatus.
2. Description of Related Art
The surgical microscope apparatus suspends a surgical microscope in midair and is used for, for example, neurosurgery. The apparatus includes a stand that is set on a floor, a longitudinal arm that is uprightly and pivotally supported with the stand, and a lateral arm that has a base end pivotally supported at an upper end of the longitudinal arm and horizontally extends from the upper end of the longitudinal arm, the surgical microscope being suspended from a front end of the lateral arm.
The surgical microscope and part of the horizontal and longitudinal arms are covered with a drape to secure an aseptic condition.
If the drape loosens and sags, it will obstruct the visibility of a surgeon. To deal with this problem, Japanese Patent Publication No. 2988980 (Patent Literature 1) discloses a technique of drawing air from the inside of the drape so that the drape may tightly be attached to the surgical microscope apparatus.

Surgical microscope apparatus and sealed drape


A device may include a sensor, a sampling unit, and an interpolator. The sensor may be configured to sense motion and output a sensed signal. The sampling unit may be configured to sample the sensed signal with a sensor clocking signal to generate a plurality of sampled values. The interpolator may be coupled to the sampling unit and may be configured to receive the plurality of sampled values, the sensor clocking signal, and a reference clocking signal external to the device. The interpolator may be configured to interpolate the plurality of sampled values based on the reference clocking signal and further based on the sensor clocking signal to generate a plurality of output values.

In general, sampling data sensed by a sensor is inaccurate because of using inaccurate clocking source. Moreover, the inaccuracy increases from one sensor to the next due to manufacturing variability as well as temperature variations. Various methods have been used to address the inaccuracies associated with sampling of the sensed data, e.g., using a host processor that resides off the sensor chip to correct for the inaccuracies, using a high frequency phase locked loop, etc. Unfortunately in applications where a host processor or a high frequency phase locked loop is used, a higher amount of power is consumed.


An apparatus and method for attaching a cover to a signature. The apparatus includes a cover applicator for securing covers to signatures, a signature supplier positioned to provide at least one signature to the cover applicator, a cover feeder positioned to feed covers in separated relation to the cover applicator, and a printer positioned between the cover feeder and the cover applicator. The printer is oriented to print onto a surface (e.g., an inner surface) of a cover fed from the cover feeder. The apparatus can further include an item feeder positioned to feed items in separated relation to the cover applicator, and an adhesive applicator positioned to deposit adhesive between the item and the cover. For example, the printer can be oriented to print on a printed area of a cover fed from the cover feeder, and the item feeder can be oriented to deposit an item onto the printed area. Preferably, the apparatus further includes an item printer positioned to print on an item fed from the item feeder.

Collating and binding systems are well known in the printing industry for mass producing printed products, such as booklets, magazines, catalogues, advertising brochures and the like. Typically, one or more sharply folded and generally pre-printed blanks or signatures are sequentially fed by a number of spaced signature feeders. The signatures are delivered such that the signatures come to rest upon a collating conveyor line which travels past the signature feeders. The conveyor gathers the signatures, one on top of the other, into a book block and moves the book block to a binding station where a cover is applied.
Recently, it has become desirable to secure items to a printed product. As used herein, the term item refers to any object that is attached to a printed product by means other than by binding, and that is smaller (e.g., in surface area) than the printed product to which it is attached. For example, it may be desirable to secure a credit card, envelope, sample packet, signature or other items to a printed product. In order to accomplish this, it is known to glue the items directly to the individual signatures, one at a time, and then provide the signatures in a shingled stream to a downstream operation (e.g., a gatherer). For example, a device known as "The Attacher", sold by Ga-Vehren Engineering, can perform this function.
It can be appreciated that the transport of signatures from the attaching device to the subsequent operation can be difficult in view of the fact that the signatures have protruding items attached to them. This can result in problems associated with smooth transport of the signatures, particularly in a shingled stream. The problem is particularly evident in the case of magazine covers, which are typically fed individually from a stack by a cover feeder. Items secured to the covers tend to interfere with feeding the covers from the stack.
The printing industry has also recognized the need for flexibility in producing different versions of the same book to be mailed to users in the same geographical location, and the value of printing personalized messages (e.g. directed to a specific consumer or group of consumers) on each book. Ink jet printing is commonly used for producing such personalized messages on these types of books.
U.S. Pat. No. 5,100,116 discloses an apparatus that can print on the full page of signatures. The disclosed printing apparatus removes signatures from a stack and separates the signatures for printing. The signatures are subsequently fed to a collating conveyor where the signatures are gathered to form a book block.

Apparatus and method for personalizing printed materials


Associating data source information with sampled runtime events allows identification of system components related to the sampled runtime events. Code can be optimized from the perspective of system components and for various architectures. A system provides a data source indication. The system associates the data source indication with a corresponding instruction instance. The instruction instance is related to a sampled runtime event, and the sampled runtime event is associated with the data source indication. The data source information and associated sampled runtime event can be supplied for profiling code.

1. Field of the Invention
The present invention relates to the field of program analysis. More specifically, the present invention relates to code profiling.
2. Description of the Related Art
Profiling code aids developers in identifying sections of code that consume excessive amounts of execution time, or which otherwise affect performance, operation or correctness of software. Profiling provides developers data that aids in accomplishing the task of optimizing code.
In general, two major classes of profiling techniques exist: code instrumentation and hardware assisted profiling. Code instrumentation techniques typically include the insertion of instructions into the instruction stream of a program to be profiled. In crude form, programmer insertion of printf source statements may be employed to profile code. More sophisticated approaches may employ compiler facilities or options to insert appropriate instruction or operations to support profiling. Upon execution of the instrumented code, execution characteristics are sampled, in part by operation of the added instructions. Typically, code instrumentation techniques impose overhead on original program code so instrumented and, unfortunately, the insertion of instructions into the instruction stream may itself alter the behavior of the program code being sampled.
Hardware assisted profiling techniques have been developed, in part, to address such limitations by off loading some aspects to dedicated hardware such as event counters. Practical implementations often employ aspects of code instrumentation and hardware assistance. In some cases, profiling support is included in, or patched into, exception handler code to avoid imposing overhead on each execution of a sampled instruction. Suitable hardware event counters are provided in advanced processor implementations such as those in accordance with the SPARC® and Alpha processor architectures. SPARC architecture based processors are available from Sun Microsystems, Inc, Santa Clara, Calif. SPARC trademarks are used under license and are trademarks or registered trademarks of SPARC International, Inc. in the United States and other countries. Products bearing SPARC trademarks are based upon an architecture developed by Sun Microsystems. Systems that include Alpha processors are available from a number of sources including Compaq Computer Corporation.
One reasonably comprehensive hardware assisted profiling environment is provided by the Digital Continuous Profiling Infrastructure (DCPI) tools that run on Alpha processor systems to provide profile information at several levels of granularity, from whole images down to individual procedures and basic blocks on down to detailed information about individual instructions, including information about dynamic behavior such as cache misses, branch mispredicts and other forms of dynamic stalls. Additional descriptive information appears in Jennifer Anderson, Lance Berc, George Chrysos, Jeffrey Dean, Sanjay Ghemawat, Jamey Hicks, Shun-Tak Leung, Mitch Lichtenberg, Mark Vandevoorde, Carl A. Waldspurger, William E. Weihl, "Transparent, Low-Overhead Profiling on Modern Processors," in Proceedings of the Workshop on Profile and Feedback-Directed Compilation in conjunction with the International Conference on Parallel Architectures and Compilation Techniques (PACT 98), Paris, France (Oct. 13, 1998).
While conventional profiling tools often provide per image, per procedure, per source line, or per instruction level profile information, these tools do not provide profile information in relation to other aspects of code behavior. In particular, conventional profiling tools do not provide information that reveals relationships between runtime events and system components. System-level analysis can indicate that particular system components have causal relationships with a relatively large proportion of runtime events. Accordingly, a technique is desirable that reveals, for a given execution sequence of code, relationships between runtime events and system components.

Associating data source information with runtime events


A method according to one embodiment includes monitoring a plurality of parameters relating to operation of a tape drive to collect data from the operation of the tape drive. A specification of one or more of the parameters to log during one or more collection windows is received. At least some of the data collected from the operation of the tape drive is logged to a memory during the one or more collection windows, where the at least some of the data collected is stored in a plurality of fields. The method further includes dynamically overlaying one or more of the fields with data corresponding to the one or more specified parameters.

The present invention relates to using extended diagnostics, and more particularly, to using overlay control for extended diagnostics for tape storage devices.
Many tape storage devices, such as an IBM® 3592/TS1140 storage tape drive, contain an internal data log for mapping measurable characteristics of the tape drive while in operation. This data log is often stored in buffer memory for retrieval and analysis. According to one particularly useful embodiment, the data log (sometimes referred to as a tape map) stores errors, significant events, operating ranges, and performance statistics for the core functional areas of the tape drive for the duration of a cartridge mount. This complex data structure is a component of a microcode dump file which is used for failure analysis by both engineering and general product support. The tape map content varies according to many factors, such as manufacturer, model, product generation, etc., but is basically a representation of a fixed set of metrics applied to the interaction between media, recording head, servo control, dataflow electronics, and microcode for a given cartridge mount.
During the course of product development and problem analysis, it is often the case where more specialized criteria and equipment are used to assess failure modes and development of optimization algorithms to improve overall read/write quality. This process is by nature iterative and experimental, with data under examination being very temporal. No method exists in the current art for porting such analytic data into an existing toolset.

This patent is subject to a terminal disclaimer.

Extended diagnostic overlay control for tape storage devices


A self-contained and integrated multi-process power spray washer apparatus to be used to clean articles placed therein, the washer apparatus including a central washing chamber which is large enough to enclose and rotate an article to be cleaned therein. A primary filter removes contaminants from a cleaning solution immediately after it has been used, and a solution reservoir receives and holds filtered cleaning solution from the primary filter. A fan forced electronic burner heats the cleaning solution contained in the reservoir, and provides a heat source for contaminant incineration. An oil skimmer removes oil and grease from an upper surface of the cleansing solution held in the reservoir, and a secondary centrifugal filter through which cleansing solution is pumped from the reservoir additionally filters the solution. A high power sprayer sprays the recycled and clean cleansing solution into the washing chamber at a substantially high volume and pressure so as to substantially clean the item contained within the washing chamber. A fresh water rinse cycle provides for a final fresh water rinse of the article being cleaned and the recycling of the contaminated water prior to reuse or proper drainage. Accordingly, three steps of a cleaning process associated with the present invention include spray washing, recycling and disposal which are fully integrated in the self contained power spray washer apparatus.

Field of the Invention
This invention relates to a self-contained and integrated multi-process power spray washer apparatus, to be used to clean any and all parts or articles placed therein, and is structured to power spray wash parts, filter and recycle cleansing solutions, and dispose of all contaminant by-product, thereby providing a cost efficient, highly effective, and environmentally acceptable means of cleaning engine parts and the like which require thorough cleaning prior to use.

Multi-process power spray washer apparatus


The transmission equipment includes a plurality of subscriber nodes which are connected serially to an optical fiber. Every node comprises an access unit with at least one directional coupler, an address detection unit, a receiver, a synchronization unit, as well as a control unit with a switching transmitter. Addressed packets continuously reach the nodes and pass through the latter via the fiber in the form of modulated light. In a first switching position, the directional coupler branches off a part of the light power of the packets from the fiber, converts the light in the optoelectrical transducer into electrical signals and reads the respective packet address in the detection unit. If this packet address matches the address of the node the control unit switches the directional coupler into a second switching position. The coupler branches off another part of the light power of the packet in this second switching position and, in so doing, feeds the occurring electrical useful signals to the receiver. The first and second switching positions differ in that a considerably greater proportion of the respective light power is branched off from the fiber in the second position than in the first switching position.

a) Field of the Invention
The invention is directed to transmission equipment with an optical transmission line to which a plurality of subscriber nodes are connected.
b) Background Prior Cut
Transmission equipment and diverse types of information transmission via transmission lines are known in general. Recently, optical transmission lines have become increasingly important for various reasons. In addition to the optical point-to-point connections, complicated network structures with optical lines are also known. For example, in an article entitled "Optical fibres in local area networks", Communications/Communications International, October 1985, pages 19 ff., B. Viklund describes various network structures with glass fiber cables for distribution networks and for networks with connections between diverse subscribers which can be set up individually. In the latter, a ring structure is most favorable. The subscriber stations of an optical transmission line of the aforementioned type are connected to the respective utilized fibers via optoelectrical couplers.
At present, there are components for optical systems, e.g. couplers, switches and modulators, based e.g. on GaAs semiconductor material which utilize electro-optical effects in order to influence light. These elements work up to frequencies in the gigahertz range (Gbit/s).
The use of address-coded packets for the transmission of information is generally known. Such packets comprise a header and an information part [hereinafter, infopart], wherein the header contains all necessary data for the respective packet and the participating devices, e.g. a destination or target address, data concerning the type of packet, monitoring bits, etc. The infopart is available for the useful information to be transmitted.
When receiving information arriving via an optical line it is unavoidable that at least a part of the light stream carrying the information is used. If the light stream on the transmission line is not regenerated in some way, then it is gradually reduced in reception nodes which are connected serially one after the other.
The connection and access nodes of such transmission equipment generally comprise electrical regenerators. The latter require optoelectrical and electro-optical transducers, so that, as a whole, this is rather a matter of mixed optical and electrical equipment.
The primary object of the invention consists in providing transmission equipment which makes do to a great extent without electrical regenerators while utilizing the aforementioned components. In this way, a system is to be provided which must be referred to as "optical" in a more literal sense than was previously the case.
This object is met by the characterizing part of the independent claims. The dependent claims show constructions of the invention.
The solution, according to the invention, makes it possible to provide flexible transmission equipment which has considerable advantages over the comparable, previously known equipment because of its more extensive optical construction. An outstanding immunity to electromagnetic interference and reduced jitter problems are to be mentioned in particular; there is also a reduction in interference sources caused by bit errors. In addition, the transmission equipment is extensively protected against the failure of individual subscriber nodes.
The invention is described in more detail in the following by way of example with reference to eight diagrams.

Transmission equipment with an optical transmission line


The present invention provides a method for the treatment of nitrogen-rich effluent and production of struvite comprising introducing the effluent in an electrolytic system and performing a first electrolytic treatment to the effluent in a first electrolytic reactor in order to organic matter that impact on nucleation of struvite, followed by a second electrolytic treatment in a second electrolytic reactor, thereby injecting Mg ions which react with NH4+ and orthophosphates from the effluent to form a struvite precipitate.

Electrocoagulation was already proposed in the late 19th and early 20th century. The use of electrocoagulation with aluminum and iron was patented in 1909 in the United States (Robinson, Australian Water & Wastewater Association, Joint NSW and Victoria State Conference in Wodonga, 22-24 Nov. 1999 (www.electropure.com.au/paper.htm); Vik et al. WaterResearch, volume 18, Issue 1, 1984, pages 1355-1360).
Coagulation is essentially to neutralize, or reduce, the electric charge of colloids and hence promote the aggregation of colloidal particles. To destabilize a suspension it is necessary that the attractive forces between particles are greater than the repulsive forces thereof. Attractive forces are mainly van der Weals forces, which act at a short distance thereof. In general, the total energy that controls the stability of the energy dispersion comprises attractive van der Weals energy of repulsion at short distance, the electrostatic energy and energy due to the steric effect of molecules solvent.
Coagulation can be done by chemical or electrical means. Alun, lime and/or polymers have been used as chemical coagulants. Chemical coagulation is becoming less popular today because of high costs associated with the chemical treatments of a significant volume of sludge and hazardous heavy metals such as metal hydroxides generated thereof in addition to the cost of chemical products needed for coagulation itself. Chemical coagulation has been used for decades.
Although the electrocoagulation mechanism resembles chemical coagulation, although, some differences benefit electrocoagulation. Indeed, electrocoagulated flocs differ from those generated by chemical coagulation. Flocs created with the electrocoagulation process tend to contain less bound water, are more resistant to shearing and are more easily filterable.
Flocs are created during the electrocoagulation water treatment with oxydo-reduction reactions. Currents of ions and charged particles, created by the electric field, increase the probability of collisions between ions and particles of opposite signs that migrate in opposite directions. This phenomenon allows the aggregation of suspended solids to form flocs.
The electrolytic reactions that take place at the electrodes are accompanied by production of micro bubbles of hydrogen (at the cathode) and oxygen (at the anode). These micro bubbles heading up will result in an upward movement of the flocs formed thereof that are recovered at the surface (this mechanism is named flotation).
The complexity of the mechanisms involved in the process of electrocoagulation in the treatment of water is not well scientifically elucidated (Yousuf et al., Journal of Hazardous Material B84, 2001). There are various features of the mechanism of the process and the geometry, or design, of the reactor in the literature. The different physico-chemical treatment, the shape of the reactor and the shape and size of electrodes affect the performance of the treatment. The wide variety of processing parameters reported in the literature and the lack of scientific data for efficient model processing and optimal processing conditions translate into a lack of development in this field. At this time, electrocoagulation is still problematic and therefore not popular (Holt et al., Colloids and Surfaces A: Physicochem. Eng. Aspects 211 (2002); Holt et al., Chemosphere 59(2005) 355-367).
The existence of an electric current in a body of water implicitly requires Faraday reactions surrounding the electrodes. The formation of chemical gradients depends on the electrolytic magnitude. The consequences of chemical reactions become more pronounced and significant in the prolonged application of electrokinetic. The effects include electrolytic of water with the simultaneous development of pH gradients and the transfer of electrolytic dissolution of the anode producing metal ions (Fe3+, Al3+, Mg2+, etc.) or cations of the electrolyte from the anode to the cathode. Chemical reactions can, in ion exchange or precipitation, form new mineral phases for cleaning water for instance.
At the cathode, the main reaction is:4H2O+4e−→2H2+40H−  (Equation 1)
The increase in hydroxyl ions can increase the precipitation of metal hydroxide. The pH of the cathode's region is basic. The following equations describe the chemical reactions at the anode:2H2O→O2+4H++4e−  (Equation 2)
If the anode is made of magnesium:Mg→Mg2++2e−  (Equation 3)
It is noted that twice as many water molecules are electrolysed at the cathode compared to the anode for the same quantity of electricity.
The struvite is a compound with a little solubility and used as a fertilizer in agricultural fields. This compound is of the formula NH4MgPO4, 6H2O and comprised PO43− and NH4+ ions, both essential to plants growth. Struvite is known as a fertilizer and have been proved potent in soils having a pH between 5.5 and 6.5.
Precipitation of struvite in a wastewater allows the elimination of the ortho-phosphate, NH4+ and magnesium present in the wastewater. Currently, processes for precipitating struvite use fluidized beds, or contained tanks reactors. In Japan, the precipitation of struvite has been tested in a sludge treatment reactor. To obtain a good performance, it is essential to optimized both nucleation and precipitation by optimizing the treatment time in the reactor and the nature of the support particles for the precipitation.
Precipitation of struvite is controlled by the pH, the supersaturation, the temperature and the presence of impurities such as calcium and can occur when the concentration in magnesium, ammonium and phosphore ions exceed the solubility product of the complex as per the following expression:Ksp=[Mg2+][NH4+][PO43−]pKs=13.26
The presence of organic matter impact on the nucleation and growth of struvite crystals and reduce the precipitation rate. In a wastewater to be treated, NH4+ and PO43− are among the components to be eliminated. While adding Mg2+ in the solution with a basic pH, the precipitate is formed. Several conditions are required for the reaction to occur:
a phosphorous concentration higher than 50 ppm
a pH value between 7 and 11, preferably between 8 and 9.2
a molar ratio Mg/P of 0.9 to 1.5
a strong agitation
a simultaneous increase in pH and temperature to reduce time of precipitation

Many patent applications have been filed for the synthesis of the struvite. WO 01/19735 discloses a process for the treatment of manure. WO 95/05347 discloses an electrolytic system using a series of electrodes. WO 2007/009749 discloses a reactor and a method for the production of struvite. U.S. Pat. No. 4,389,317 discloses the chemical reduction of phosphates in water. WO 00/56139 discloses a method for preventing the formation of struvite in fish cans.
WO 2009/102142 discloses a two-steps treatment of an effluent, wherein the effluent is first treatment in an anaerobic reactor followed by a second treatment producing the struvite.
Therefore, there exists a need in the art for an improved method, system and apparatus for optimizing the production of struvite by an electrolytic treatment of a waste effluent over the existing art. There is a need in the art for such a method, system and apparatus for treating an effluent that can be easily installed, economically manufactured and operated. And there is a very perceptible need for an improved method, system and apparatus for treating wastewater over the existing art.

Method for simultaneous elimination of orthophosphate and ammonium using electrolytic process


Systems for producing hydrogen-rich gases including rapid response plasma fuel converters are provided. The rapid response plasma fuel converters systems are suitable for use in vehicles and the like in which the systems are capable of instantaneously providing hydrogen-rich gas, reducing pollutants during vehicle startup and allowing use of hydrogen-rich gas during load changes. The systems are preferably capable of responding on the order of a second or less. The systems include a plasma fuel converter for receiving hydrocarbon fuel and reforming the hydrocarbon fuel into a hydrogen-rich gas, an internal combustion engine adapted to receive the hydrogen-rich gas from the plasma fuel converter, a generator powered by the engine and connected to deliver electrical energy to power the plasma fuel converter, and a power supply circuit capable of rapidly providing power to the plasma fuel converter in response to a stimulus. The stimulus can be movement in the accelerator pedal controlled by the driver of the vehicle. The plasma fuel converters can be operated pulsed or non-pulsed modes of operation and can utilize arc or high frequency discharges. The plasma fuel converter can be either separated from the engine or directly integrated into the engine to allow for more efficient use of the thermal energy produced by the plasma fuel converter.

Hydrogen is attractive as a fuel or additive for internal combustion engines because hydrogen as a fuel source can significantly reduce air pollution and can also serve as an alternative energy source to gasoline. See Mishchenko, et al., Proc. VII World Hydrogen Energy Conference, Vol. 3 (1988), Belogub, et al., Int. J. Hydrogen Energy, Vol. 16, 423 (1991), Varde, et al., Hydrogen Energy Progress V, Vol. 4 (1984), Feucht, et al., Int. J. Hydrogen Energy, Vol 13, 243 (1988), Chuveliov, et al., In: Hydrogen Energy and Power Generation, T. Nejat Veziroglu, Ed., Nova Science Publisher, New York, N.Y. (1991), Das, Int. J. Hydrogen Energy, Vol 16, 765 (1991). Moreover, engine efficiency can be 10-50% higher when running on hydrogen as compared with a gasoline engine. Prior art systems contemplated either storing hydrogen on-board or generating it on board. On-board storage requires high pressure vessels, cryogenic containers if the hydrogen is to be stored as a compressed gas or liquid, or large getter volumes and weights if the hydrogen is to be stored as a hydride. Moreover, the refill time for hydrogen is substantially longer than that for gasoline when the hydrogen is to be stored on-board.
As to the on-board production of hydrogen, several approaches have been disclosed in the prior art. For example, U.S. Pat. No. 5,143,025 to Munday discloses the use of electrolysis to separate water into hydrogen and oxygen and introducing the hydrogen into an internal combustion engine. In U.S. Pat. No. 5,159,900 to Dammann, hydrogen gas is produced by water interaction with solid carbon. Electrical current is passed between the carbon electrodes causing the electrodes to burn and oxidize to form carbon monoxide and hydrogen. U.S. Pat. No. 5,207,185 to Greiner et al. discloses a burner which utilizes a portion of the hydrocarbon fuel to reform another portion to produce hydrogen. The hydrogen is then mixed with the hydrocarbon fuel for introduction into an internal combustion engine.
Another system diverts a fraction of the gasoline from the flow path to the engine and is passed through a thermal converter and steam reformed to yield hydrogen-rich gas. See, Breshears, et al., Proc. of EPA 1st Symposium on Low Pollution Power Systems Development, 268 (1973). We note that the authors state that this system would not be practical to generate hydrogen as the sole fuel for an engine. Yet another system of this type uses partial oxidation in a catalytic converter to produce hydrogen rich gas. See Houseman, et al., Proc. 3rd World Hydrogen Energy Conf., 949 (1980). This system requires carefully controlled catalytic action and temperature range and has limitations for startup and transient response.
U.S. Pat. Nos. 5,425,332 and 5,437,250, both to Rabinovich et al., disclose plasmatron-internal combustion engine systems. The systems disclosed include a source of hydrocarbon fuel which is supplied to a plasmatron which reforms the fuel into a hydrogen-rich gas. Plasmatrons heat an electrically conducting gas either by an arc discharge or by a high frequency inductive or microwave discharge. An internal combustion engine is connected to receive the hydrogen-rich gas from the plasmatron. While these systems are significant improvements over the prior art, it would be desirable to provide systems that are capable of rapid response for instantaneously providing hydrogen-rich gas, reducing pollutants during startup and allowing use of hydrogen-rich gas during typical load changes. The entire contents of both U.S. Pat. Nos. 5,425,332 and 5,437,250 are incorporated herein by reference.

Rapid response plasma fuel converter systems