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Proceedings Paper

Polarization in CdTe radiation detectors at high X-ray photon fluxes (Conference Presentation)
Author(s): Jan Franc; Václav Dědič; Jakub Pekárek; Eduard Belas; Jan Touš
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Paper Abstract

In this contribution we show an improvement of a spectroscopic response of CZT X-ray detector operating at high fluxes of X-ray tube by simultaneous infrared light illumination with a wavelength of 1200 nm. CZT detectors usually suffer from a polarization effect while their internal electric field can be strongly deformed due to a trapping of photogenerated holes. We describe a mechanism of an optically induced depolarization peaking at photon energy of about 1 eV (~1240 nm) due to an optical transition of electrons from the valence band to the deep level. The depolarization effect is accompanied by a decrease of the detector current which results in a lower noise entering the preamplifier of detector readout circuit. We have observed that it is possible to restore originally distorted X-ray spectra using additional 1200 nm LED illumination with a photon flux of ~10^16 cm^-2s^-1 at approximately two times higher X-ray flux than without LED. The number of detected counts was in the range of 10^5-10^6mm^2s^-1. The restoration of the spectrum by continuous infrared light is accompanied by decrease of dark current. We explain this effect by light induced changes of profile of the electric filed that leads to decrease of the electron current injected from the cathode.

Paper Details

Date Published: 2 November 2016
PDF: 1 pages
Proc. SPIE 9968, Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XVIII, 996807 (2 November 2016); doi: 10.1117/12.2239473
Show Author Affiliations
Jan Franc, Charles Univ. in Prague (Czech Republic)
Václav Dědič, Charles Univ. in Prague (Czech Republic)
Jakub Pekárek, Charles Univ. in Prague (Czech Republic)
Eduard Belas, Charles Univ. in Prague (Czech Republic)
Jan Touš, Crytur Ltd (Czech Republic)

Published in SPIE Proceedings Vol. 9968:
Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XVIII
Ralph B. James; Michael Fiederle; Arnold Burger; Larry Franks, Editor(s)

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