From Event: SPIE Optical Engineering + Applications, 2016
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.
Jan Franc, Václav Dědič, Jakub Pekárek, Eduard Belas, and Jan Touš, "Polarization in CdTe radiation detectors at high X-ray photon fluxes
(Conference Presentation)," Proc. SPIE 9968, Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XVIII, 996807 (Presented at SPIE Optical Engineering + Applications: August 29, 2016; Published: 2 November 2016); https://doi.org/10.1117/12.2239473.5178382300001.
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