高能伽玛源下碲锌镉探测器的针孔成像

Pinhole imaging using CdZnTe detector for high-energy gamma source

采用新型室温碲锌镉(CdZnTe)辐射探测器,通过厚针孔系统对137Cs高能662 keV伽玛射线辐射源进行成像探测,得到了能谱图和放射源图像。计算分析了高能射线穿透效应对空间分辨力的影响,并对不同偏压下得到的图像进行比较与讨论。实验表明,当放大倍率不大时(小于3),高能射线对准直器材料的穿透效应增大是限制图像空间分辨力的主要因素,探测器像素尺寸的大小对图像空间分辨力的影响并不明显。随偏置电压升高,探测器得到的图像会得到改善,但过大的偏压(大于1 000 V)会使晶体内部的电场不均匀性增大,降低信噪比从而降低图像品质。

Based on a new room-temperature CdZnTe detector,the energy spectrum of each pixel and the image of the 662 keV 137Cs source have been obtained with a thick pinhole system.According to penetration and scattering effect of the high energy photons in pinhole,the degradation of system spatial resolution was analyzed,and the images derived at different bias voltage were analyzed and compared.The experiments indicate that,the equivalent diameter,caused by penetration and scattering effect of the high energy photons,is the main reason for the degradation of system spatial resolution when the magnification is smaller than 3,and the influence of the pixel size is subtle.The quality of image would be improved when the bias voltage increases.However,extremely high voltage（higher than 1 000 V） would enhance the non-uniformity of electrical field in the crystal,and thus lower the image quality.