Experimental study of the response of semiconductor detectors for EDXRF analysis

Sunil K Valaparla, University of Texas at El Paso

Abstract

This present work relates to the study and characterization of the response function of an energy-dispersive x-ray spectrometer. The problems of energy, efficiency and resolution calibration of the system operating in the energy (5-60 keV) range are discussed. We present the operation characteristics of the portable pyro-electric x-ray generator (COOL-X) and the application of the calibrated response spectrum in the elemental analysis using X-ray Fluorescence (XRF). Use of COOL-X as a source of exciting radiation in combination with high resolution semiconductor detectors applied to XRF presents a practical advantage due to the price and small form factor of the components. ^ The detectors and the COOL-X used in the present study are produced by Amptek. We study the response of the Si(Li)-Pin XR-100CR semiconductor detector to low energy photons. The photopeak efficiency was determined experimentally by using radioisotopes 55Fe, 241Am, 137Cs and 133Ba and compared against a theoretical efficiency curve. The efficiency for γ photons resulting from the decay of the radioactive sources and that of x-rays, was obtained from direct measurements. The response characteristics of CdTe XR-100T detector and the efficiency calculations are performed using 55Fe, 241Am, and 133Ba. Escape events originated in this detector are observed and discussed. The comparison between the detectors and the advantages and disadvantages for XRF are described, together with a discussion of suggested features or expected complications that may arise given certain parameters of the detectors. Given the working conditions of the detectors at hand, one outcome has been that, for the low energies, below 25 keV, the Si(Li)-PIN detector has better energy resolution, lower background counts. For higher energy x-rays, above 25 keV, CdTe has better stopping power, which improves its efficiency. The former, are general considerations made by the manufacturer [13] that are here confirmed. ^ Analysis of energies and intensities of fluorescent x-rays emitted from a given material when atoms are bombarded with electrons or photons has been successfully used for non-destructive elemental analysis. We present a brief analysis of elemental content carried out by means of a pyro-electric generator in combination with a CdTe and a Si(Li)-Pin energy dispersive detectors. The setup presented here can be easily assembled in an average laboratory to observe the effect of X-rays as they interact with matter to yield a characteristic fingerprint, a phenomenon that directly relates to atomic theory. In the present case three pieces of metal whose elemental content has been characterized were analyzed and their elemental content shown. Additionally we performed the elemental analysis using a Si(Li)-Pin detector on standard reference materials and their elemental energy lines have been identified. These results have been compared with those obtained from an X-ray analysis system XMET 3000 TXV+, also based on a Si-Pin detector but with a Silver X-ray excitation source. Such a system has been used to estimate the elemental mass fraction (%).^

Subject Area

Physics, Nuclear|Physics, Atomic|Engineering, Materials Science

Recommended Citation

Valaparla, Sunil K, "Experimental study of the response of semiconductor detectors for EDXRF analysis" (2009). ETD Collection for University of Texas, El Paso. AAI1468970.
http://digitalcommons.utep.edu/dissertations/AAI1468970

Share

COinS