Using the pixellated CdZnTe detector, the radiation imaging experiment for the Rh target X-ray source was accomplished. The experimental results indicate that the response signals of the anode pixels, which distribute over the center irradiated area, are completely shut-off when the tube voltage is 45 kV and the tube current increases to 20 μA. Moreover, the non-response pixel area expands with the increase of the tube current, and the total event count of the CdZnTe detector reduces obviously. Furthermore, the inner electric potential and electric field distributions of the pixellated CdZnTe detector were simulated based on the Poisson equation. The simulation results reveal that the accumulation of the hole carriers, which results from the extremely low drift ability of the hole carrier, leads to a relatively high space-charge-density area in the CdZnTe bulk when the irradiated photon flux increases to 5× 105 mm-2 · s-1. And thus, the induced signal screen effect of the anode pixels in the center irradiated area is mainly attributed to the distorted electric field which makes electron carriers drift toward the high potential area in the CdZnTe crystal instead of the pixel anodes.%采用铑(Rh)靶45 kV X射线源进行了碲锌镉(CdZnTe)面元像素阵列探测器成像实验.实验结果表明:在探测距离1 mm,管电压45 kV条件下,管电流增大至20μA时,辐照中心区域像素单元信号丢失,出现围绕辐照中心区域的边缘高事件计数环形探测图像.随着管电流的增大,无响应像素区域扩大,探测器总体事件计数明显降低.进一步根据泊松方程建立了CdZnTe晶体内部电势分布模型,仿真结果表明:单位面积光子通量为5×105 mm-2·s-1时,由于CdZnTe晶体较低的空穴迁移率,晶体内部存在堆积空穴载流子形成的高空间电荷密度分布区域.晶体内部电场产生扭曲,电子载流子无法迁移至对应阳极位置,导致辐照中心区域产生信号屏蔽效应.
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