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SENSITIVITY ANALYSIS TO EVALUATE THE TRANSPORT PROPERTIES OF CdZnTe DETECTORS USING ALPHA PARTICLES AND LOW-ENERGY GAMMA-RAYS

  • Kim, Kyung-O (Department of Nuclear Engineering, Hanyang University) ;
  • Ahn, Woo-Sang (Department of Radiation Oncology, Asan Medical Center) ;
  • Kwon, Tae-Je (Department of Nuclear Engineering, Hanyang University) ;
  • Kim, Soon-Young (RADCORE Co., Ltd.) ;
  • Kim, Jong-Kyung (Department of Nuclear Engineering, Hanyang University) ;
  • Ha, Jang-Ho (Advanced Radiation Detection Instrument & Sensor Lab, Korea Atomic Energy Research Institute)
  • Received : 2010.09.09
  • Accepted : 2011.06.01
  • Published : 2011.12.25

Abstract

A sensitivity analysis of the methods used to evaluate the transport properties of a CdZnTe detector was performed using two different radiations (${\alpha}$ particle and gamma-ray) emitted from an $^{241}Am$ source. The mobility-lifetime products of the electron-hole pair in a planar CZT detector ($5{\times}5{\times}2\;mm^3$) were determined by fitting the peak position as a function of biased voltage data to the Hecht equation. To verify the accuracy of these products derived from ${\alpha}$ particles and low-energy gamma-rays, an energy spectrum considering the transport property of the CZT detector was simulated through a combination of the deposited energy and the charge collection efficiency at a specific position. It was found that the shaping time of the amplifier module significantly affects the determination of the (${\mu}{\tau}$) products; the ${\alpha}$ particle method was stabilized with an increase in the shaping time and was less sensitive to this change compared to when the gamma-ray method was used. In the case of the simulated energy spectrum with transport properties evaluated by the ${\alpha}$ particle method, the peak position and tail were slightly different from the measured result, whereas the energy spectrum derived from the low-energy gamma-ray was in good agreement with the experimental results. From these results, it was confirmed that low-energy gamma-rays are more useful when seeking to obtain the transport properties of carriers than ${\alpha}$ particles because the methods that use gamma-rays are less influenced by the surface condition of the CZT detector. Furthermore, the analysis system employed in this study, which was configured by a combination of Monte Carlo simulation and the Hecht model, is expected to be highly applicable to the study of the characteristics of CZT detectors.

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