利用二维平台扫描系统研究光电倍增管阴极位置响应

Study of Position Response of PMT Photocathode By Using a Two-dimensional Scanning System

大型高海拔空气簇射观测站(LHAASO)计划中的各种探测器将使用几万只光电倍增管测量探测器收集到的光子数,光电倍增管阴极位置响应的均匀性是影响探测器能量分辨的重要因素之一。为此搭建了由步进电机驱动的二维扫描平台控制LED光源,逐毫米扫描光电倍增管光阴极,测量光源照射光阴极不同位置时的阳极输出信号。实验中对多种候选光电倍增管进行了测试,研究其位置响应的均匀性。结果表明聚焦电极、管内电场分布结构造成的光电子收集效率的差异是造成位置响应差异的主要因素。

In the Large High Altitude Air Shower Observatory project,photomultiplier tubes（PMTs） will be used to measure the number of photons collected by different detectors.The position response of PMT photocathode is one of the main factors affecting the detector energy resolution.A two-dimensional scanning system is constructed to guide a LED light source scanning over a PMT photocathode millimeter by millimeter,while the anode signal is measured.Several candidate PMTs are tested for study of their photocathode position responses.The results show that the position response is caused by the photoelectron collection efficiency due to focus electrode and electric field distribution inside the PMT.Different kinds of PMTs show different position responses.