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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

Evaluation of the x-ray response of a position-sensitive microstrip detector with an integrated readout chip

Description: The performance of an SVX silicon microstrip detector and its compatible integrated readout chip have been evaluated in response to Rh K{alpha} x-rays (average energy 20.5 keV). The energy and spatial discrimination capabilities, efficient data management and fast readout rates make it an attractive alternative to the CCD and PDA detectors now being offered for x-ray position sensitive diffraction and EXAFS work. The SVX system was designed for high energy physics applications and thus further development of the existing system is required to optimize it for use in practical x-ray experiments. For optimum energy resolution the system noise must be decreased to its previously demonstrated low levels of 2 keV FWHM at 60 keV or less, and the data handling rate of the computer must be increased. New readout chips are now available that offer the potential of better performance. 15 refs., 7 figs.
Date: August 1, 1990
Creator: Rossington, C.; Jaklevic, J.; Haber, C.; Spieler, H. (Lawrence Berkeley Lab., CA (USA)) & Reid, J. (California Univ., Davis, CA (USA). Dept. of Physics)
Partner: UNT Libraries Government Documents Department

Application of kinetic inductance thermometers to x-ray calorimetry

Description: A kinetic inductance thermometer is applied to x-ray calorimetry, and its operation over a wide range of frequencies and geometries is discussed. Three amplifier configurations are described, one using a superconducting quantum interference device (SQUID) amplifier, another incorporating an FET amplifier in an amplitude modulated system, and the third, using a tunnel diode frequency modulated oscillator circuit. The predicted performance of each configuration is presented. 13 refs., 6 figs., 1 tab.
Date: August 13, 1990
Creator: Wai, Y.C.; Labov, S.E. & Silver, E.H.
Partner: UNT Libraries Government Documents Department

Simulations of NOVA direct-drive Rayleigh-Taylor experiments

Description: Directly driven Rayleigh-Taylor instability growth experiments being performed on NOVA have been simulated using the computer code, LASNEX. These experiments employ beams smoothed with random phase plates (RPP), and will later include smoothing by spectral dispersion (SSD). Samples are CH foils with or without imposed sinusoidal surface perturbations. Perturbation growth is diagnosed by means of x-ray backlighting. Calculated growth rates are fairly flat across the wavelength range of 20--80 {mu}m which can be accessed experimentally, and are moderately suppressed below classical growth rates. Perturbations of large enough initial amplitude that the contrast in the x-ray image is measurable from the start of the experiment quickly grow into the nonlinear regime. Smaller initial amplitudes result in a longer interval of linear growth, but the initial perturbation will not be detectable in the data. Structure which is predicted to develop from speckles in the RPP beam pattern, with and without SSD, is also presented.
Date: November 3, 1990
Creator: Weber, S.V.
Partner: UNT Libraries Government Documents Department

Linear, position-sensitive x-ray detector used for real-time calculations of small-angle scattering parameters with submillisecond resolution

Description: The advent of high-intensity X-ray synchrotron sources has made possible the measurement of fluctuations in small-angle scattering parameters from typical specimens on a submillisecond time scale in real-time. The fundamental design of any fast detector system optimized for such measurements will incorporate some type of solid state detector array capable of rapid encoding algorithms. A prototype with a self-scanning photodiode array has been designed and tested at beamline 1 to 4 at the Stanford Synchrotron Radiation Laboratory (SSRL), and the results indicate that the device will operate at speeds yielding submillisecond temporal resolution in real-time.
Date: January 1, 1984
Creator: Borso, C.S.
Partner: UNT Libraries Government Documents Department

Models of optical and soft x-ray spectra in AM Her stars

Description: The AM Her systems are widely believed to be cataclysmic variable systems in which the white dwarf has a magnetic field strong enough to lock the white dwarf to the companion star. The magnetic field channels the accretion flow to the magnetic polar caps of the white dwarf where the gas passes through a strong shock and the accretion energy is released. The continuum spectra of the AM Her systems have three major components: the ir/optical component, the EUV/soft x-ray component, and the hard x-ray component. Models of the AM Her systems generally agree that the hard x-rays are free-free radiation emitted by the hot postshock gas and that the optical component is electron cyclotron emission from the postshock gas. The soft x-ray component is less well understood, primarily because it is very soft (temperature less than 100 eV) and thus is very difficult to measure accurately with current instruments. Models agree that some soft x-ray emission will arise from hard x-rays and cyclotron radiation that is absorbed at the stellar surface and re-radiated, but other sources of soft x-rays have also been suggested. Thus it is important to develop models for the soft x-ray spectrum. This paper presents some preliminary results on the emission in all spectral bands based on numerical models of the accretion flow. 4 figs.
Date: May 25, 1987
Creator: Langer, S.H.
Partner: UNT Libraries Government Documents Department

Use of synchrotron radiation for electron identification at high luminosity

Description: Synchrotron radiation has been used successfully to identify electrons of 10 to 30 GeV traversing a field length of 30 kG-m. Since comparable field lengths are a feature of many proposed collider detectors, and since this is an electron energy range of interest at ..sqrt..s approx. = 1 TeV, we consider whether such a device could be useful in the L = 10/sup 33/ environment.
Date: January 1, 1983
Creator: Aronson, S.
Partner: UNT Libraries Government Documents Department

Microchannel plate pinhole camera for 20 to 100 keV x-ray imaging

Description: We present the design and construction of a sensitive pinhole camera for imaging suprathermal x-rays. Our device is a pinhole camera consisting of four filtered pinholes and microchannel plate electron multiplier for x-ray detection and signal amplification. We report successful imaging of 20, 45, 70, and 100 keV x-ray emissions from the fusion targets at our Novette laser facility. Such imaging reveals features of the transport of hot electrons and provides views deep inside the target.
Date: October 3, 1984
Creator: Wang, C.L.; Leipelt, G.R. & Nilson, D.G.
Partner: UNT Libraries Government Documents Department

Semiconductor detectors for fluorescent EXAFS

Description: The subject of silicon semiconductor detectors in the limited context of their use in Extended X-ray Absorption Fine Structure (EXAFS) studies using synchrotron radiation is discussed and the special considerations which enter into their use in these applications are examined.
Date: April 1, 1978
Creator: Goulding, F.S.; Jaklevic, J.M. & Thompson, A.C.
Partner: UNT Libraries Government Documents Department

The Los Alamos megamp fiber z-pinch experiment

Description: The HDZP-II experiment uses a 2 MV, 1.9 {Omega}, 1.2 MA, 100 ns risetime pulsed-power driver. Preliminary experiments have been performed at 600--800 kA (half the bank energy). Preliminary results show the plasma heating to several kilovolts (although a non-Maxwellian distribution is likely) while maintaining an overall straight and reasonably uniform axial configuration. However, interferograms and x-ray pinhole photographs show the column expanding rapidly with considerable small-scale structure, presumably due to m=0 activity. The neutron yield (typically 5 {times} 10{sup 9}) is consistent with thermonuclear reactions at the reduced density although detailed study of the neutron characteristics has not been performed. Preliminary isotropy measurements do not show significant neutron anisotropy. 10 refs.
Date: January 1, 1990
Creator: Scudder, D.W.; Shlachter, J.S.; Hammel, J.E.; Venneri, F.; Chrien, R. (Los Alamos National Lab., NM (USA)); Lovberg, R. et al.
Partner: UNT Libraries Government Documents Department

Pulse widths effects on scintillator saturation

Description: A test was performed over an extensive range of irrradiance (approximately five orders of magnitude) to see to what extent organic scintillators responded linearly with x-ray input. At the highest levels of irradiance achievable with the experimental configuration, but only for pulses in the region of 4.0 ns or wider, a degree of nonlinear response was observed for some of the scintillators. The data suggest that at levels below 1 mJ/cm/sup 2/-ns it is safe to asume that for pulses 6.5 ns and shorter there is no significant level of nonlinearity to x rays with spectrum. For the cases of undoped NE111 and NE111 doped with 10 percent benzophenone, experimental conditions were such that it was possible to accumulate data significantly above the 1 mJ/cm/sup 2/-ns level of irradiance. It is with these cases that a nonlinear response was observed. It is assumed that the same nonlinearity would have also been noticed had experimental conditions been such that equivalent levels of irradiance could have been achieved at the time the other samples were studied.
Date: August 1, 1978
Creator: Kohler, D.A. & Chase, L.F.
Partner: UNT Libraries Government Documents Department

X-ray reflectivity measurements of surface roughness using energy dispersive detection

Description: We describe a new technique for measuring x-ray reflectivity using energy dispersive x-ray detection. The benefits of this method are the use of a fixed scattering angle and parallel detection of all energies simultaneously. These advantages make the technique more readily useable with laboratory x-ray sources and more compatible with growth chambers. We find excellent agreement between the calculated Fresnel reflectivity and the reflectivity obtained from a smooth Ge (001) surface. Reflectivities obtained during 500 eV Xe ion bombardment of Ge surfaces demonstrate the sensitivity of the technique to be better than 1 {angstrom}. 9 refs., 4 figs.
Date: January 1, 1990
Creator: Chason, E. & Warwick, D.T.
Partner: UNT Libraries Government Documents Department

Photoemission measurements for low energy x-ray detector applications

Description: Photoemission has been studied for nearly 100 years as both a means of investigating quantum physics, and as a practical technique for transducing optical/x-ray photons into electrical currents. Numerous x-ray detection schemes, such as streak cameras and x-ray sensitive diodes, exploit this process because of its simplicity, adaptability, and speed. Recent emphasis on diagnostics for low temperature, high density, and short-lived, plasmas for inertial confinement fusion has stimulated interest in x-ray photoemission in the sub-kilovolt regime. In this paper, a review of x-ray photoemission measurements in the 50 eV to 10 keV x-ray region is given and the experimental techniques are reviewed. A semiempirical model of x-ray photoemission is discussed and compared to experimental measurements. Finally, examples of absolutely calibrated instruments are shown.
Date: January 1, 1981
Creator: Day, R.H.
Partner: UNT Libraries Government Documents Department

Measurements with a 35 psec gate time microchannel plate camera

Description: Measurements of the x-ray gate time of 0.2 mm thick microchannel plates with an L/D aspect ratio of 20 as opposed to the more usual L/D=40, demonstrate that gate times of 35 ps can be achieved. Good agreement with time dependent modelling is demonstrated. 7 refs., 4 figs., 2 tabs.
Date: July 1, 1990
Creator: Bell, P.E.; Kilkenny, J.D.; Hanks, R. & Landen, O.
Partner: UNT Libraries Government Documents Department

Application of a one-dimensional position-sensitive detector to a Kratky small-angle x-ray camera

Description: A conventional Kratky small-angle collimation system has been modified to allow the use of a one-dimensional position-sensitive x-ray detector. The detector was designed specifically for use with a long-slit camera and has uniform sensitivity over the entire beam in the slit-length direction. Procedures for alignment of the collimation system are given, and a variety of tests of the performance of the system are presented. Among the latter are measurements of electronic noise and parasitic scattering as well as comparisons against samples which were also measured on other cameras. The good agreement of these comparisons demonstrates the success of the use of a position-sensitive detector with the Kratky collimation system.
Date: January 1, 1979
Creator: Russell, T.P.; Stein, R.S.; Kopp, M.K.; Zedler, R.E.; Hendricks, R.W. & Lin, J.S.
Partner: UNT Libraries Government Documents Department

High speed gated x-ray imagers

Description: Single and multi-frame gated x-ray images with time-resolution as fast as 150 psec are described. These systems are based on the gating of microchannel plates in a stripline configuration. The gating voltage comes from the avalanche breakdown of reverse biased p-n junction producing high power voltage pulses as short as 70 psec. Results from single and four frame x-ray cameras used on Nova are described. 8 refs., 9 figs.
Date: January 1, 1988
Creator: Kilkenny, J.D.; Bell, P.; Hanks, R.; Power, G.; Turner, R.E. & Wiedwald, J.
Partner: UNT Libraries Government Documents Department

The MPI/AIT X-ray Imager (MAXI): High speed pn-CCD's for x-ray detection

Description: MAXI (MPI/AIT X-RAY Imager) is part of a proposal submitted to the European Space Agency (ESA) as focal plane instrumentation of the X-ray Multi Mission (XMM). Within a collaboration of 13 European institutes we have proposed a fully depleted (sensitive) pn CCD of 280 {mu}m thickness with a homogeneous sensitive area of 36 cm{sup 2} and a pixel size of 150 {times} 150 {mu}m{sup 2} which is well matched with the telescope's angular resolution of 30 arcsec, translating to a position resolution of approximately 1 mm in the focal plane. The X-ray sensitivity is higher than 90% from 250 eV up to 10 keV, the readout time in the full frame mode of the complete focal plane will be 2 ms with a readout noise of better than 5 e{sup {minus}} (rms). Prototypes of all individual components of the camera system have been fabricated and tested. The camera concept will be presented. The measured transfer properties of the CCD and the on-chip electronics will be treated. Taking into account the coupling of the on-chip amplifier to the following front-end electronics the expected performance will be derived.
Date: June 1, 1989
Creator: Strueder, L.; Braeuninger, H.; Meier, M.; Predehl, P.; Reppin, C.; Sterzik, M. et al.
Partner: UNT Libraries Government Documents Department

One-dimensional curved wire chamber for powder x-ray crystallography

Description: A xenon filled single anode wire chamber with delay line readout has been constructed for use in powder x-ray crystallography using 8 to 20 keV x-rays. The entire chamber including the anode wire and the delay line which forms part of the cathode plane is a section of a circular arc whose center is the powder specimen. The anode wire--38 ..mu..m gold-plated tungsten--is suspended in a circular arc by the interaction of a current flowing through it and magnetic field provided by two permanent magnets, above and below the wire, extending along the active length of the chamber. When filled with xenon to 3 atmospheres the chamber has uniform sensitivity in excess of 80% at 8 keV and a spatial resolution better than 0.3 mm.
Date: January 1, 1978
Creator: Ortendahl, D.; Perez-Mendez, V.; Stoker, J. & Beyermann, W.
Partner: UNT Libraries Government Documents Department

An imaging x-ray microscope using a laser plasma source and a Schwarzchild objective

Description: This paper presents some design considerations for an imaging x-ray microscope to be used in the water window'' region of the spectrum. The usefulness of such an instrument is discussed. The suitability of current soft x-ray sources and optics are discussed, and the selection of a laser plasma source and a multilayer coated Schwarzchild objective is justified. Also, problems associated with the production of figured multilayer coatings for the water window'' region are discussed. 2 refs.
Date: January 1, 1990
Creator: Pew, H.K. & Stradling, G.L.
Partner: UNT Libraries Government Documents Department

Test results of a prototype dielectric microcalorimeter

Description: The initial development work on a dielectric microcalorimeter is presented. It focuses on the dielectric properties of the ferroelectric material KTa{sub 1-x}Nb{sub x}O{sub 3} (KTN). Measurements of the temperature dependent dielectric constant are given together with the first alpha particle detection results from a prototype composite microcalorimeter operating at 1.3 K. a non-thermal mechanism for detecting 6 MeV alpha particles in a monolithic KTN sample is also reported. 7 refs, 16 figs., 1 tab.
Date: August 13, 1990
Creator: Pfafman, T.E.; Silver, E.; Labov, S. (Lawrence Livermore National Lab., CA (USA)); Beeman, J.; Goulding, F.; Hansen, W. et al.
Partner: UNT Libraries Government Documents Department

Design, performance, and calibration of the ALEXIS ultrasoft x-ray telescopes

Description: The Array of Low Energy X-ray Imaging Sensors (ALEXIS) experiment consists of six wide angle EUV/ultrasoft x-ray telescopes utilizing normal incidence multilayer mirrors, flown a miniature satellite to map out the sky in three narrow bandpasses around 66, 71, and 95 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 95 eV bandpass has a higher throughput and is more sensitive to continuum sources. The mission will be launched into orbit on the Pegasus Air Launched Vehicle in mid-1991. We will present the details of the ALEXIS telescope optical design, initial characterizations of the first flight mirrors and detectors, and the current schemes for characterizing and calibrating the completed telescope assemblies. We will also discuss the details of a novel wavetrap'' feature incorporated into the multilayer mirror structure to greatly reduce the mirror's reflectivity at 304 {angstrom}, a major background contamination flux of He II emission from the geocorona. 2 refs., 13 figs.
Date: January 1, 1990
Creator: Bloch, J.J.; Ameduri, F.; Priedhorsky, W.C.; Roussel-Dupre, D.; Smith, B.W. (Los Alamos National Lab., NM (USA)); Siegmund, O.H.W. et al.
Partner: UNT Libraries Government Documents Department

X-ray diodes for laser fusion plasma diagnostics

Description: Photodiodes with x-ray sensitive photocathodes are commonly used as broadband x-ray detectors in fusion plasma diagnostics. We have measured the risetime of the detector system and have measured the quantum efficiency between 1 to 500 A of numerous photocathode materials of practical interest. The materials studied include aluminum, copper, nickel, gold, three forms of carbon, chromium, and cesium iodide. The results of the measurements are compared with Henke's semiempirical model of photoyield. We have studied the effects of long-term cathode aging and use as a plasma diagnostic on cathode quantum efficiency. In addition, we have measured the x-ray mass-absorption coefficient of several ultrasoft x-ray windows in energy regions where data were unavailable. Windows studied were made of aluminum, Formvar, polypropylene, and Kimfoil. Measurements between 1 to 50 A were performed with the Los Alamos Scientific Laboratory's low-energy x-ray calibration facility, and the measurements between 50 to 550 A were performed at the National Bureau of Standard's synchrotron ultraviolet radiation facility.
Date: February 1, 1981
Creator: Day, R.H.; Lee, P.; Saloman, E.B. & Nagel, D.J.
Partner: UNT Libraries Government Documents Department

X-ray and charged particle detection with CsI(Tl) layer coupled to a-Si:H photodiode layers

Description: A compact real-time X-ray and charged particle imager with digitized position output can built either by coupling a fast scintillator to a photodiode array or by forming one on a photodiode array directly. CsI(Tl) layers 100--1000{mu}m thick were evaporated on glass substrates from a crystal CsI(Tl). When coupled to a crystalline Si or amorphous silicon (a-Si:H) photodiode and exposed to calibrated X-ray pulses, their light yields and speed were found to be comparable to those of a crystal CsI(Tl). Single {beta} particle detection was demonstrated with this combination. The light spread inside evaporated CsI(Tl) was suppressed by its columnar structure. Scintillation detection gives much larger signals than direct X-ray detection due to the increased energy deposition in the detector material. Fabrication of monolithic type X-ray sensors consisting of CsI + a-Si:H photodiodes is discussed. 20 refs., 16 figs.
Date: October 1, 1990
Creator: Fujieda, I.; Cho, G.; Drewery, J.; Gee, T.; Jing, T.; Kaplan, S.N. et al.
Partner: UNT Libraries Government Documents Department