Signal modeling of charge sharing effect in simple pixelated CdZnTe detector
Signal modeling of charge sharing effect in simple pixelated CdZnTe detector
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DOI：
10.3938/jkps.64.1336
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发表时间：
2014-05-01
影响因子：
0.6
通讯作者：
He, Zhong
中科院分区：
文献类型：
--
作者：
Kim, Jae Cheon;Kaye, William R.;He, Zhong
为了研究 3D 位置敏感像素化 CdZnTe (CZT) 探测器中的能量分辨率退化，开发了详细的探测器系统建模包并用于分析探测器性能。对具有 11 x 11 简单像素阳极阵列和 1.72 mm 像素间距的 20 x 20 x 15 mm(3) CZT 晶体进行了建模。 VAS UM/TAT4 专用集成电路 (ASIC) 用于信号读出。仿真包的组件包括伽马射线与 CZT 晶体的相互作用、电荷感应、电子噪声、脉冲整形和 ASIC 触发程序。电荷感应模型考虑像素之间的电荷漂移、捕获、扩散和共享。该系统模型用于确定电子云共享、加权潜在不均匀性和加权潜在串扰的影响，这些影响会针对不同的伽马射线相互作用位置产生不均匀的信号响应，并最终降低能量分辨率。已经研究了像素之间的间隙下方加权电势的降低对事件总脉冲幅度的影响。由像素之间的间隙附近收集的电子云引起的瞬态信号可能会产生虚假信号，并且测量到的幅度甚至可能大于光峰值。随着收集电荷的像素数量增加，由于电荷共享而发生旁邻事件的概率显着增加。如果旁邻事件没有得到适当校正，多像素事件中像素化 CZT 探测器的能量分辨率会迅速下降。
In order to study the energy resolution degradation in 3D position-sensitive pixelated CdZnTe (CZT) detectors, a detailed detector system modeling package has been developed and used to analyze the detector performance. A 20 x 20 x 15 mm(3) CZT crystal with an 11 x 11 simple-pixel anode array and a 1.72 mm pixel pitch was modeled. The VAS UM/TAT4 Application Specific Integrated Circuitry (ASIC) was used for signal read-out. Components of the simulation package include gamma-ray interactions with the CZT crystal, charge induction, electronic noise, pulse shaping, and ASIC triggering procedures. The charge induction model considers charge drift, trapping, diffusion, and sharing between pixels. This system model is used to determine the effects of electron cloud sharing, weighting potential non-uniformity, and weighting potential cross-talk which produce non-uniform signal responses for different gamma-ray interaction positions and ultimately degrade energy resolution. The effect of the decreased weighting potential underneath the gap between pixels on the total pulse amplitude of events has been studied. The transient signals induced by electron clouds collected near the gap between pixels may generate false signals, and the measured amplitude can be even greater than the photopeak. As the number of pixels that collect charge increases, the probability of side-neighbor events due to charge sharing significantly increases. If side-neighbor events are not corrected appropriately, the energy resolution of pixelated CZT detectors in multiple-pixel events degrades rapidly.