公共格栅像素CdZnTe探测器的能谱特性

使用同一块CdZnTe晶体设计制作了像素大小不等的4×4公共格栅像素CdZnTe探测器。通过能谱测定实验及权重势和电场仿真,研究了公共格栅像素CdZnTe探测器中的小像素效应和引导效应。结果表明:由于小像素效应较弱,较大的像素不能有效消除"空穴拖尾",能谱特性较差;由于晶体内部以及像素和公共格栅间隙表层的电荷损失,较小的像素能谱特性也较差。在像素宽度为0.8 mm时,得到了对662keV的137Cs放射源的最佳能量分辨率3.80%和峰谷比5.65。适当增大公共格栅偏压可以引导电子向阳极像素运动,促进电荷的完全收集,改善探测器的能谱特性。过大的偏压则会造成像素和公共格栅间表面漏电流的增加,探测器的能谱特性也会恶化。在像素宽度为0.8mm时最佳偏压为-60V。

Spectroscopic characteristics of common-grid pixelated CdZnTe detectors

A 44 common-grid pixelated CdZnTe detector with different pixel sizes is designed and fabricated using the CdZnTe crystal. By the spectra measurement combined with weighting potential and electric field simulation, the small pixel effect and guide effect in common-grid pixelated CdZnTe detector are investigated. Results show that the spectroscopic characteristics of lager pixels are degraded since the small pixel effect is not strong enough to remove the hole trailing. While the spectroscopic characteristics of smaller pixels are also degraded since the serious charge loss in volume and surface layer between pixels and common-grid. An optimal energy resolution of 3.80% FWHM at 662 keV(137Cs radiation source) is obtained from the 0.8 mm wide pixel. Excessive high bias voltage increases the surface leakage current between pixels and common-grid, which in turn degrades the spectroscopic characteristics. The optimal bias voltage is -60 V for 0.8 mm wide pixel.