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Development and application of photosensitive device systems to studies of biological and organic materials. Progress report, January 1, 1993--December 31, 1993

Description: This progress report summarizes results, as of August, 1993, for DOE grant DE-FG-02-76ER60522 during the fiscal period 1/1/93 to 12/31/93, which is the first year of a 3-year grant cycle. The overall goals of the grant are to develop advanced x-ray detector technologies, especially as applicable for biological and materials research at the national laboratories, and to train graduate and post-doctoral students on the use of these technologies via the performance of original biological and materials research. As summarized below, there has been good progress toward achieving the research goals of the original 3-year proposal; in consequence, the research plan and the total budget for the rest of 1993 and beyond is still well described by the original proposal. Accomplishments since the last progress report include: (A) A 1k x 1k fiber optically coupled CCD detector was assembled, tested at CHESS and is slated for extended user trials this Fall. A 2k x 2k CCD detector is being assembled for permanent installation at CHESS. (B) X-ray detector phosphors, calibration techniques, and system software have been developed. (C) The design of a Pixel Array Detector, a collaborative project with the Advanced Photon Source, has been initiated. (D) The properties of biomembrane lipids under extremes of pressure have been investigated. High pressure instrumentation and techniques have been developed. (E) The physics of mesophase formation in biomembrane lipid, surfactant, and polymeric systems have been studied. This includes study of the interaction of membrane proteins with elastically strained lipid bilayers. (G) Work has been initiated on the use of thermal diffuse scatter from proteins as a probe of protein dynamics. (H) Studies on luminescent phenomena have been reported. Since the last progress report (dated 15 May 1992), this work has resulted in 10 published papers, 7 abstracts, 1 Ph.D. thesis and 1 technical report.
Date: September 14, 1993
Creator: Gruner, S. M. & Reynolds, G. T.
Partner: UNT Libraries Government Documents Department

Spectroscopic diagnostics of high temperature plasmas. [Annual report]

Description: A three-year research program for the development of novel XUV spectroscopic diagnostics for magnetically confined fusion plasmas is proposed. The new diagnostic system will use layered synthetic microstructures (LSM) coated, flat and curved surfaces as dispersive elements in spectrometers and narrow band XUV filter arrays. In the framework of the proposed program we will develop impurity monitors for poloidal and toroidal resolved measurements on PBX-M and Alcator C-Mod, imaging XUV spectrometers for electron density and temperature fluctuation measurements in the hot plasma core in TEXT or other similar tokamaks and plasma imaging devices in soft x-ray light for impurity behavior studies during RF heating on Phaedrus T and carbon pellet ablation in Alcator C-Mod. Recent results related to use of multilayer in XUV plasma spectroscopy are presented. We also discuss the latest results reviewed to q{sub o} and local poloidal field measurements using Zeeman polarimetry.
Date: December 31, 1990
Creator: Moos, W.
Partner: UNT Libraries Government Documents Department

Wire chamber gases

Description: In this paper, we describe new developments in gas mixtures which have occurred during the last 3--4 years. In particular, we discuss new results on the measurement and modeling of electron drift parameters, the modeling of drift chamber resolution, measurements of primary ionization and the choice of gas for applications such as tracking, single electron detection, X-ray detection and visual imaging. In addition, new results are presented on photon feedback, breakdown and wire aging.
Date: April 1, 1992
Creator: Va`vra, J.
Partner: UNT Libraries Government Documents Department

Laboratory Directed Research and Development Program. Annual report

Description: This report briefly discusses the following research: Advances in Geoexploration; Transvenous Coronary Angiography with Synchrotron X-Rays; Borehole Measurements of Global Warming; Molecular Ecology: Development of Field Methods for Microbial Growth Rate and Activity Measurements; A New Malaria Enzyme - A Potential Source for a New Diagnostic Test for Malaria and a Target for a New Antimalarial Drug; Basic Studies on Thoron and Thoron Precursors; Cloning of the cDNA for a Human Serine/Threonine Protein Kinase that is Activated Specifically by Double-Stranded DNA; Development of an Ultra-Fast Laser System for Accelerator Applications; Cluster Impact Fusion; Effect of a Bacterial Spore Protein on Mutagenesis; Structure and Function of Adenovirus Penton Base Protein; High Resolution Fast X-Ray Detector; Coherent Synchrotron Radiation Longitudinal Bunch Shape Monitor; High Grain Harmonic Generation Experiment; BNL Maglev Studies; Structural Investigations of Pt-Based Catalysts; Studies on the Cellular Toxicity of Cocaine and Cocaethylene; Human Melanocyte Transformation; Exploratory Applications of X-Ray Microscopy; Determination of the Higher Ordered Structure of Eukaryotic Chromosomes; Uranium Neutron Capture Therapy; Tunneling Microscopy Studies of Nanoscale Structures; Nuclear Techiques for Study of Biological Channels; RF Sources for Accelerator Physics; Induction and Repair of Double-Strand Breaks in the DNA of Human Lymphocytes; and An EBIS Source of High Charge State Ions up to Uranium.
Date: December 1, 1992
Creator: Ogeka, G. J. & Romano, A. J.
Partner: UNT Libraries Government Documents Department

Extreme ultraviolet and soft x-ray diagnostics of high-temperature plasmas. Progress report

Description: This report describes recent progress and plans for calendar year 1987 in the Johns Hopkins University program to develop and improve spectroscopic diagnostics for the high temperature plasmas used in magnetic fusion research. An EUV spectrograph which provides time resolved spectra along fifteen chords of a plasma device has been completed and evaluation on DIII-D will began in late 1986. Other instrumentation work includes the evaluation of a sensitive detector for ion temperature/velocity distribution determinations and a feasibility study of Zeeman polarimetry for determining magnetic fields. A comprehensive data set taken on the TEXT tokamak is undergoing analysis as a means of improving the ionic parameters used in diagnostic studies and to expand the capabilities of existing instruments. Potential new advanced in spectroscopic technology are being monitored to determine if they provide advantages for fusion research.
Date: October 2, 1986
Creator: Moos, W.
Partner: UNT Libraries Government Documents Department

The NSLS 100 element solid state array detector

Description: X-ray absorption studies of dilute samples require fluorescence detection techniques. Since signal-to-noise ratios are governed by the ratio of fluorescent to scattered photons counted by a detector, solid state detectors which can discriminate between fluorescence and scattered photons have become the instruments of choice for trace element measurements. Commercially available 13 element Ge array detectors permitting total count rates < 500,000 counts per second are now in routine use. Since x-ray absorption beamlines at high brightness synchrotron sources can already illuminate most dilute samples with enough flux to saturate the current generation of solid state detectors, the development of next-generation instruments with significantly higher total count rates is essential. We present the design and current status of the 100 element Si array detector being developed in a collaboration between the NSLS and the Instrumentation Division at Brookhaven National Laboratory. The detecting array consists of a 10*10 matrix of 4mm * 4mm elements laid out on a single piece of ultra-high purity silicon mounted at the front end of a liquid nitrogen dewar assembly. A matrix of charge sensitive integrating preamplifiers feed signals to an array of shaping amplifiers, single channel analyzers, and scalers. An electronic switch, delay amplifier, linear gate, digital scope, peak sensing A to D converter, and histogramming memory module provide for complete diagnostics and channel calibration. The entire instrument is controlled by a LabView 2 application on a MacII ci; the software also provides full control over beamline hardware and performs the data collection.
Date: December 31, 1991
Creator: Furenlid, L. R.; Kraner, H. W.; Rogers, L. C.; Stephani, D.; Beuttenmuller, R. H.; Beren, J. et al.
Partner: UNT Libraries Government Documents Department

Development and application of photosensitive device systems to studies of biological and organic materials. Third year progress report, January 1, 1992--December 31, 1992

Description: This report describes progress as of the third year of a 3-year DoE grant for 1/1/92 to 12/31/92. Because this is the last year of a 3- year grant cycle, this report will summarize progress over the entire 3-year period. The overall goals of the grant are to develop novel instrumentation and techniques for the performance of biological and materials research, and especially for the development of x-ray detectors suitable for use at storage ring sources. Research progress has been excellent and the overall goals, as well as most of the specific goals have been successfully met.
Date: May 15, 1992
Creator: Gruner, S. M. & Reynolds, G. T.
Partner: UNT Libraries Government Documents Department

Large area, low capacitance Si(Li) detectors for high rate x-ray applications

Description: Large area, single-element Si(Li) detectors have been fabricated using a novel geometry which yields detectors with reduced capacitance and hence reduced noise at short amplifier pulse-processing times. A typical device employing the new geometry with a thickness of 6 mm and an active area of 175 mm 2 has a capacitance of only 0.5 pf, compared to 2.9 pf for a conventional planar device with equivalent dimensions. These new low capacitance detectors, used in conjunction with low capacitance field effect transistors, will result in x-ray spectrometers capable of operating at very high count rates while still maintaining excellent energy resolution. The spectral response of the low capacitance detectors to a wide range of x-ray energies at 80 K is comparable to typical state-of-the-art conventional Si(Li) devices. In addition to their low capacitance, the new devices offer other advantages over conventional detectors. Detector fabrication procedures, I-V and C-V characteristics, noise performance, and spectral response to 2-60 keV x-rays are described.
Date: October 1, 1992
Creator: Rossington, C. S.; Fine, P. M. & Madden, N. W.
Partner: UNT Libraries Government Documents Department

The ALEXIS data processing package: An update

Description: The ALEXIS experiment (Array of Low Energy X-ray Imaging Sensors), is a mini-satellite containing six wide angle EUV/ultrasoft x-ray telescopes. Its purpose is to map out the sky in three narrow (5%) bandpasses around 66, 71, and 93 eV. The 66 and 71 eV bandpasses are centered on intense Fe emission lines which are characteristic of million-degree plasmas such as the one thought to produce the soft x-ray background. The 93 eV bandpass is not near any strong emission lines and is more sensitive to continuum sources. The mission will be launched on the Pegasus Air-Launched Vehicle in early 1993 into a 400-nautical-mile, high-inclination orbit and will be controlled entirely from a small ground station located at Los Alamos. The project is a collaborative effort between Los Alamos National Laboratory, Sandia National Laboratory, and the University of California-Berkeley Space Sciences Laboratory.
Date: February 1, 1993
Creator: Bloch, J. J.; Smith, B. W. & Edwards, B. C.
Partner: UNT Libraries Government Documents Department

X-ray holographic microscopy using the atomic-force microscope

Description: The present authors have been seeking for some time to improve the resolution of holographic microscopy and have engaged in a continuing series of experiments using the X1A soft x-ray undulator beam line at Brookhaven. The principle strategy for pushing the resolution lower in these experiments has been the use of polymer resists as x-ray detectors and the primary goal has been to develop the technique to become useful for examining wet biological material. In the present paper the authors report on progress in the use of resist for high-spatial-resolution x-ray detection. This is the key step in in-line holography and the one which sets the ultimate limit to the image resolution. The actual recording has always been quite easy, given a high-brightness undulator source, but the difficult step was the readout of the recorded pattern. The authors describe in what follows how they have built a special instrument: an atomic force microscope (AFM) to read holograms recorded in resist. They report the technical reasons for building, rather than buying, such an instrument and they give details of the design and performance of the device. The authors also describe the first attempts to use the system for real holography and the authors show results of both recorded holograms and the corresponding reconstructed images. Finally, the authors try to analyze the effect that these advances are likely to have on the future prospects for success in applications of x-ray holography and the degree to which the other technical systems that are needed for such success are available or within reach.
Date: September 1, 1993
Creator: Howells, M. R.; Jacobsen, C. J. & Lindaas, S.
Partner: UNT Libraries Government Documents Department

Gamma Large Area Silicon Telescope (GLAST)

Description: The recent discoveries and excitement generated by EGRET have prompted an investigation into modern technologies ultimately leading to the next generation space-based gamma ray telescope. The goal is to design a detector that will increase the data acquisition rate by almost two orders of magnitude beyond EGRET, while at the same time improving on the angular resolution, the energy measurement of reconstructed gamma rays, and the triggering capability of the instrument. The GLAST proposal is based on the assertion that silicon particle detectors are the technology of choice for space application: no consumables, no gas volume, robust (versus fragile), long lived, and self triggering. The GLAST detector is roughly modeled after EGRET in that a tracking module precedes a calorimeter. The GLAST Tracker has planes of thin radiatior interspersed with planes of crossed-strip (x,y) 300-{mu}m-pitch silicon detectors to measure the coordinates of converted electron-positron pairs. The gap between the layers ({approximately}5 cm) provides a lever arm in track fitting resulting in an angular resolution of 0.1{degree} at high energy (the low energy angular resolution at 100 MeV would be about 2{degree}, limited by multiple scattering). A possible GLAST calorimeter is made of a mosaic of Csl crystals of order 10 r.l. in depth, with silicon photodiodes readout. The increased depth of the GLAST calorimeter over EGRET`s extends the energy range to about 300 GeV.
Date: November 1, 1993
Creator: Godfrey, G. L.
Partner: UNT Libraries Government Documents Department

Enhanced columnar structure in CsI layer by substrate patterning

Description: Columnar structure in evaporated CsI layers can be controlled by patterning substrates as well as varying evaporation conditions. Mesh-patterned substrates with various dimensions were created by spin-coating polyimide on glass or amorphous silicon substrates and defining patterns with standard photolithography technique. CsI(Tl) layers 200--1000 {mu}m were evaporated. Scintillation properties of these evaporated layers, such as light yield and speed, were equivalent to those of the source materials. Spatial resolution of X-ray detectors consisting of these layers and a linear array of X-ray detectors consisting of these layers and a linear array of Si photodiodes was evaluated by exposing them to a 25{mu}m narrow beam of X-ray. The results obtained with 200{mu}m thick CsI layers coupled to a linear photodiode array with 20 dots/mm resolution showed that the spatial resolution of CsI(Tl) evaporated on patterned substrates was about 75 {mu}m FWHM, whereas that on CsI(Tl) on flat substrates was about 230 {mu}m FWHM. Micrographs taken by SEM revealed that these layers retained the well-defined columnar structure originating from substrate patterns. Adhesion and light transmission of CsI(Tl) were also improved by patterning the substrate.
Date: October 1, 1991
Creator: Jing, T.; Cho, G.; Drewery, J.; Kaplan, S. N.; Mireshghi, A.; Perez-Mendez, V. et al.
Partner: UNT Libraries Government Documents Department

Issues concerning solid state detectors for EXAFS

Description: Fluorescence extended x-ray absorption fine structure spectroscopy (EXAFS) is a commonly used technique in conjunction with x-ray synchrotron radiation for studying the local atomic structure of dilute elements in biological, geological and materials systems. Due to the nature of the EXAFS technique, and the difficulties associated with the detection of low energy x-rays, EXAFS has been used primarily in the energy range above 5 keV. However, there are a number of elements of interest with K- or L-absorption edges below 5 keV, which have not been easily accessible with existing EXAFS instrumentation. Several characteristics of solid state detectors must be optimized for use in low energy EXAFS measurements. The detector entrance window, or ``dead layer,`` must be as thin as possible to minimize the attenuation of the fluorescent signal. The detector spectral backgrounds must be minimized so that the tailing background on the low energy side of the scattered photopeak is as low as possible to maximize the S/N of the fluorescent photopeak. Based on our work, a thin Pd surface barrier contact on a Si(Li) detector offers the thinnest detector dead layer and also the lowest spectral background for the Si(Li) and Ge detectors studied to date. To maximize the S/N, the detectors must be operated at as high a count rate as possible, without compromising detector energy resolution. High count rates can be achieved using multiple detector arrays; close packing of the detector elements can further increase the S/N by utilizing the ``best`` portion of the scattered polarized synchrotron beam.
Date: October 1, 1991
Creator: Rossington, C. S.; Giauque, R. D. & Jaklevic, J. M.
Partner: UNT Libraries Government Documents Department

A direct comparison of Ge and Si(Li) detectors in the 2--20 keV range

Description: The spectral response of high purity Ge (HPGe) and lithium-drifted Si (Si(Li)) surface barrier detectors of similar geometry has been measured over a range of x-ray energies under identical experimental conditions. Detector characteristics such as spectral background, escape peak intensity, entrance window absorption, and energy resolution are presented and compared. Although these characteristic have been discussed in the literature previously, this paper represents an attempt to consolidate the information by making comparisons under equivalent experimental conditions for the two types of detectors. A primary goal of the study is a comparison of the two types of detectors for use in x-ray fluorescence applications.
Date: October 1, 1991
Creator: Rossington, C. S.; Giauque, R. D. & Jaklevic, J. M.
Partner: UNT Libraries Government Documents Department

Amorphous silicon pixel layers with cesium iodide converters for medical radiography

Description: We describe the properties of evaporated layers of Cesium Iodide (Thallium activated) deposited on substrates that enable easy coupling to amorphous silicon pixel arrays. The CsI(Tl) layers range in thickness from 65 to 220{mu}m. We used the two-boat evaporator system to deposit CsI(Tl) layers. This system ensures the formation of the scintillator film with homogenous thallium concentration which is essential for optimizing the scintillation light emission efficiency. The Tl concentration was kept to 0.1--0.2 mole percent for the highest light output. Temperature annealing can affect the microstructure as well as light output of the CsI(Tl) film. 200--300C temperature annealing can increase the light output by a factor of two. The amorphous silicon pixel arrays are p-i-n diodes approximately l{mu}m thick with transparent electrodes to enable them to detect the scintillation light produced by X-rays incident on the CsI(Tl). Digital radiography requires a good spatial resolution. This is accomplished by making the detector pixel size less then 50{mu}m. The light emission from the CsI(Tl) is collimated by techniques involving the deposition process on pattered substrates. We have measured MTF of greater than 12 line pairs per mm at the 10% level.
Date: November 1, 1993
Creator: Jing, T.; Cho, G. & Goodman, C. A.
Partner: UNT Libraries Government Documents Department

Fast photoconductor CdTe detectors for synchrotron x-ray studies

Description: The Advanced Photon Source will be that brightest source of synchrotron x-rays when it becomes operational in 1996. During normal operation, the ring will be filled with 20 bunches of positrons with an interbunch spacing of 177 ns and a bunch width of 119 ps. To perform experiments with x-rays generated by positrons on these time scales one needs extremely high speed detectors. To achieve the necessary high speed, we are developing MBE-grown CdTe-base photoconductive position sensitive array detectors. The arrays fabricated have 64 pixels with a gap of 100 {mu}m between pixels. The high speed response of the devices was tested using a short pulse laser. X-ray static measurements were performed using an x-ray tube and synchrotron radiation to study the device`s response to flux and wavelength changes. This paper presents the response of the devices to some of these tests and discusses different physics aspects to be considered when designing high speed detectors.
Date: September 1, 1993
Creator: Yoo, Sung Shik; Faurie, J. P.; Wang, Kemei; Montano, P. A.; Qiang, Huang & Rodricks, B.
Partner: UNT Libraries Government Documents Department

Self-recovering superconducting strip detectors

Description: Using a 1.8 {mu}m wide superconducting strip made of granular tungsten, we have observed self-recovering pulses when the detector is irradiated with a {sup 55}Fe 6 keV X-rays source. For low values of the bias current (i.e. I{sub b}<30{mu}A at T{sub b}=1.5K) the superconducting state is recovered in 10--50 ns giving voltage pulses across the strip of few hundred {mu}v in amplitude. At high bias currents the detector did not self-recover and a constant counting efficiency has measured at different operating temperatures. There are good indications that this high counting rate can be extended to all the reduced bias currents where the detector is able to reset itself after every switch. The current threshold between collapsing and propagating switches and the time evolution of the voltage pulses can be described using a thermal propagation model developed in previous works. The ability of detectors to automatically recover the superconducting state in a short period of time after sensing a particle is encouraging in the feasibility study of fast superconducting microvertex detectors and also confirm the potential application of superconducting strips as high fast resolution X-rays detectors.
Date: September 1, 1991
Creator: Gabutti, A. & Gray, K. E.
Partner: UNT Libraries Government Documents Department

Gas proportional detectors with interpolating cathode pad readout for high track multiplicities

Description: New techniques for position encoding in very high rate particle and photon detectors will be required in experiments planned for future particle accelerators such as the Superconducting Super Collider and new, high intensity, synchrotron sources. Studies of two interpolating cathode ``pad`` readout systems are described in this thesis. They are well suited for high multiplicity, two dimensional unambiguous position sensitive detection of minimum ionizing particles and heavy ions as well as detection of x-rays at high counting rates. One of the readout systems uses subdivided rows of pads interconnected by resistive strips as the cathode of a multiwire proportional chamber (MWPC). A position resolution of less than 100 {mu}m rms, for 5.4 keV x-rays, and differential non-linearity of 12% have been achieved. Low mass ({approximately}0.6% of a radiation length) detector construction techniques have been developed. The second readout system uses rows of chevron shaped cathode pads to perform geometrical charge division. Position resolution (FWHM) of about 1% of the readout spacing and differential non-linearity of 10% for 5.4 keV x-rays have been achieved. A review of other interpolating methods is included. Low mass cathode construction techniques are described. In conclusion, applications and future developments are discussed. 54 refs.
Date: December 1, 1991
Creator: Yu, Bo
Partner: UNT Libraries Government Documents Department

Properties of melt-grown ZnSe solid-state radiation detectors

Description: Zinc Selenide (ZnSe) crystals grown using the High Pressure Bridgman (HPB) technique were used to fabricate solid-state radiation detectors measuring 10 x 10 x 2 mm{sup 3}. Sputtered platinum and gold contacts were applied to polished detector blanks. Voltage versus current characteristics were determined for the devices at 25 C. Pulse height spectra were obtained using {sup 241}Am and {sup 109}Cd at both 25 C and 150 C with applied bias of 9,000 V/cm. Current versus temperature was measured over the temperature range of 30 C to 150 C. Performance was measured at energies of 22.1 and 59.5 keV over a temperature range of {minus}70 C to 170 C. Current versus dose rate was measured with 662 keV gamma irradiation. A value of the Mobility-Lifetime product ({mu}{tau}) for electrons was estimated. Time and temperature dependence of photo-peak position using Pulse Height Analysis (PHA) was studied.
Date: December 1, 1994
Creator: Eissler, E. E. & Lynn, K. G.
Partner: UNT Libraries Government Documents Department

Reciprocal space analysis of the microstructure of luminescent and nonluminescent porous silicon films

Description: The microstructure of anodically prepared porous silicon films was determined using a novel X-ray diffraction technique. This technique uses double-crystal diffractometry combined with position-sensitive X- ray detection to efficiently and quantitatively image the reciprocal space structure of crystalline materials. Reciprocal space analysis of newly prepared, as well as aged, p{sup {minus}} porous silicon films showed that these films exhibit a very broad range of crystallinity. This material appears to range in structure from a strained, single-crystal, sponge-like material exhibiting long-range coherency to isolated, dilated nanocrystals embedded in an amorphous matrix. Reciprocal space analysis of n{sup +} and p{sup +} porous silicon showed these materials are strained single-crystals with a spatially-correlated array of vertical pores. The vertical pores in these crystals may be surrounded by nanoporous or nanocrystalline domains as small as a few nm in size which produce diffuse diffraction indicating their presence. The photoluminescence of these films was examined using 488 nm Ar laser excitation in order to search for possible correlations between photoluminescent intensity and crystalline microstructure.
Date: December 31, 1994
Creator: Lee, S. R.; Barbour, J. C.; Medernach, J. W.; Stevenson, J. O. & Custer, J. S.
Partner: UNT Libraries Government Documents Department

Design studies for ITER x-ray diagnostics

Description: Concepts for adapting conventional tokamak x-ray diagnostics to the harsh radiation environment of ITER include use of grazing-incidence (GI) x-ray mirrors or man-made Bragg multilayer (ML) elements to remove the x-ray beam from the neutron beam, or use of bundles of glass-capillary x-ray ``light pipes`` embedded in radiation shields to reduce the neutron/gamma-ray fluxes onto the detectors while maintaining usable x-ray throughput. The x-ray optical element with the broadest bandwidth and highest throughput, the GI mirror, can provide adequate lateral deflection (10 cm for a deflected-path length of 8 m) at x-ray energies up to 12, 22, or 30 keV for one, two, or three deflections, respectively. This element can be used with the broad band, high intensity x-ray imaging system (XIS), the pulseheight analysis (PHA) survey spectrometer, or the high resolution Johann x-ray crystal spectrometer (XCS), which is used for ion-temperature measurement. The ML mirrors can isolate the detector from the neutron beam with a single deflection for energies up to 50 keV, but have much narrower bandwidth and lower x-ray power throughput than do the GI mirrors; they are unsuitable for use with the XIS or PHA, but they could be used with the XCS; in particular, these deflectors could be used between ITER and the biological shield to avoid direct plasma neutron streaming through the biological shield. Graded-d ML mirrors have good reflectivity from 20 to 70 keV, but still at grazing angles (<3 mrad). The efficiency at 70 keV for double reflection (10 percent), as required for adequate separation of the x-ray and neutron beams, is high enough for PHA requirements, but not for the XIS. Further optimization may be possible.
Date: January 1, 1995
Creator: Hill, K. W.; Bitter, M.; von Goeler, S. & Hsuan, H.
Partner: UNT Libraries Government Documents Department

Bragg crystal polarimeter for the Spectrum-X-Gamma mission

Description: We are designing a Bragg crystal polarimeter for the focal plane of the SODART telescope on the Spectrum-X-Gamma mission. A mosaic graphite crystal will be oriented at 45{degree} to the optic axis of the telescope, thereby preferentially reflecting those x-rays which satisfy the Bragg condition and have electric vectors that are perpendicular to the plane defined by the incident and reflected photons. The reflected x-rays will be detected by an imaging proportional counter with the image providing direct x-ray aspect information. The crystal will be {approx}50 {mu}m thick to allow x-rays with energies {ge}4 keV to be transmitted to a lithium block mounted below the graphite. The lithium is used to measure the polarization of these high energy x-rays by exploiting the polarization dependence of Thomson scattering. The development of thin mosaic graphite crystals is discussed and recent reflectivity, transmission, and uniformity measurements are presented. 8 refs., 11 figs., 1 tab.
Date: August 13, 1990
Creator: Holley, J.; Silver, E.; Ziock, K.P. (Lawrence Livermore National Lab., CA (USA)); Novick, R.; Kaaret, P. (Columbia Univ., New York, NY (USA). Columbia Astrophysics Lab.); Weisskopf, M. et al.
Partner: UNT Libraries Government Documents Department

Development and application of photosensitive device systems to studies of biological and organic materials

Description: This report discusses the following basic research accomplishments: new x-ray structure determination methods were developed and applied to biomembrane lipid phases; a novel mechanism for general anesthesia was proposed; the elastic properties of membranes were investigated, both theoretically and experimentally; the effects of high pressures on membranes were studied; neutron diffraction was used to probe mesophase structure; and novel lipid and surfactant systems are characterized. Also discussed are instrumentation accomplishments.
Date: July 12, 1990
Creator: Gruner, S.M. & Reynolds, G.T.
Partner: UNT Libraries Government Documents Department