X-Ray Fluorescence Analysis Capability of HgI 2 Detector Systems
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X-RAY FLUORESCENCE ANALYSIS CAPABILITY OF HGI 2 DETECTOR SYSTEMS Y.J.WANG AND J.S.IWANCZYK, Xsirius, Inc., 4640 Admiralty Way, Suite 214, Marina del Rey, CA 90292 ABSTRACT A laboratory XRF analysis system employing an HgI 2 spectrometer detector has been built. The system consists of an x-ray generator tube, a rotating carousel holding multiple XRF targets, and a probe head containing the HgI 2 detector. Tests have been performed on several samples, under vacuum, helium and nitrogen ambient atmospheric conditions. This is of particular interest, since the applications for such an XRF system include operation under different ambient conditions. For applications in terrestrial and space planetary exploration, the expected temperatures and gas ambient will vary widely. Comparative analyses using the various gases were made on spectra obtained from standard geological samples. I. INTRODUCTION
A. X-ray fluorescence spectrometry X-ray secondary-emission spectrometry, or x-ray fluorescence spectrometry (XRFS), is a nondestructive instrumental method of qualitative and quantitative elemental analysis. The basic principle underlying x-ray fluorescence analysis (XRF) is the following: a collection of atoms, the sample, is excited by x-ray photons. The excited sample atoms decay back to their ground states by emitting fluorescent x-rays, whose energies (or wavelengths) are uniquely characteristic of the elemental identity of the atom emitting them. These emitted x-rays are collected and used as an indication of the composition of the sample. Excitation, detection and spectral analysis are the three major steps in energy dispersive XRF analysis [1]. Gas-filled detectors, scintillation counters, and semiconductor detectors are all commonly employed in analytical x-ray spectrometry. In these detectors the incident x-ray photons are converted to pulses of electric current, which are then processed by the electronics. Qualitative and quantitative x-ray spectrometric analysis can be done by using either energy- or wavelengthdispersive (crystal diffracting) detection systems. However, in the energy-dispersive technique, photons corresponding to all of the x-ray spectral lines emitted by the specimen can be accumulated simultaneously. Further, the x-ray beam losses in diffracting at low efficiency through one or more crystals in a wavelength-dispersive instrument can be avoided. Thus, energy dispersive x-ray spectrometers permit analyses to be performed much more rapidly and conveniently than wavelength dispersive spectrometers. B. Hg12 x-ray spectrometers Gas-filled detectors, scintillation counters and semiconductor detectors such as Si[Li], Ge[Li] and HPGe have been commonly used for a variety of applications, however, for a specific application and an energy range, there are advantages and disadvantages associated with each kind of detector. Systems utilizing cryogenically cooled Ge[Li] and HPGe detectors have very good detection efficiency and energy resolutions, but lack the possibility of portability, which is required for ma
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