Journal of X-Ray Science and Technology - Volume 6, issue 4

Authors: Egarievwe, S. U. | Chen, K.-T. | Burger, A. | James, R. B. | Lisse, C. M.

Article Type: Research Article

Abstract: We have studied the behavior of Cd1–x Znx Te detectors in the temperature range 24–70°C. The detector count rate stability and leakage currents are presented as a function of voltage, time, and temperature. Detector polarization due to bulk and surface effects leading to a decreased leakage current was observed. At 70°C, the position of the 32 keV photopeak of 133 Ba was stable with time. The peak position varies within only 3 keV, and the peak quality factor varied between 0.31 and 0.41, for a 24 h period of operation at a 60 V bias. The net count to total …count ratio was also stable, with values varying between 0.56 and 0.59. The net count to total count ratio decreased from 0.78 at 25°C to 0.71 at 60°C. The conclusion is that Cd1–x Znx Te is a promising material for gamma ray detection at temperatures above room temperature. Show more

DOI: 10.3233/XST-1996-6401

Citation: Journal of X-Ray Science and Technology, vol. 6, no. 4, pp. 309-315, 1996

Authors: Davis, T. J.

Article Type: Research Article

Abstract: The imaging properties of perfect crystals, used for controlling and directing x-ray beams in imaging systems, are analyzed using optical transfer functions. The optical transfer functions are related to the point-spread functions for the crystal imaging system and are derived from a one-dimensional Fourier transform of the Takagi—Taupin equations. Images obtained using diffracting crystals as optical elements are simulated for the Laue and Bragg geometries using a Fourier transform method and the imaging characteristics of each of these crystal configurations are analyzed. It is demonstrated that the perfect crystals act as spatial filters of the object wave.

DOI: 10.3233/XST-1996-6402

Citation: Journal of X-Ray Science and Technology, vol. 6, no. 4, pp. 317-342, 1996

Authors: Giakos, G. C. | Ghotra, P. | Pillai, B. | Chowdhury, S. | Vedantham, S. | DiBianca, F. A. | Jordan, L. M. | Devidas, S. | Nagarajan, S. | Endorf, R.J.

Article Type: Research Article

Abstract: A systematic study of the line spread function (LSF) in the drift direction of a high-pressure ionization chamber for x-ray detection and imaging is presented. Experimental results, obtained by operating a KCD krypton-filled detector at pressures up to 60 atm and constant electric field-to-gas pressure ratio, indicate that the width of the LSF increases with the drift distance and decreases with increasing pressure, both effects being quite large. The hypothesis of this paper is that, at sufficiently high pressures, formation of clusters of molecular ions with a unique or narrowed mobility distribution take place by means of energy exchange mechanisms. …Therefore, the LSF of the ionic signal becomes narrower and the FWHM of the ionic signal improves significantly with increasing gas pressure. This research is aimed at investigating methods to improve the spatial resolution as part of the development of a large field-of-view prototype digital radiographic scanner operating on kinestatic charge detection principles. Show more

DOI: 10.3233/XST-1996-6403

Citation: Journal of X-Ray Science and Technology, vol. 6, no. 4, pp. 343-358, 1996

Authors: Pelletier, J. F. | Chaker, M. | Kieffer, J. C.

Article Type: Research Article

Abstract: A transmission grating spectrometer has been coupled to a high-temporal-resolution soft x-ray streak camera for the study of picosecond laser-plasma x-ray sources. A procedure to deconvolve the overlapping contributions of diffraction orders and to calibrate the instrument has been established in order to obtain absolute time-resolved x-ray emission spectra in the 0.1–1.2 keV spectral region. The deconvolution and calibration techniques are presented along with measurements establishing the temporal resolution of this diagnostic at ~2 ps. Examples of calibrated spectra of laser-plasma x-ray sources created by 400 fs laser pulses at intensities of 1018 W/cm2 are also shown.

DOI: 10.3233/XST-1996-6404

Citation: Journal of X-Ray Science and Technology, vol. 6, no. 4, pp. 359-374, 1996