大面积光电倍增管地磁场效应测试系统

Test system for the earth-magnetic effect of large-area photomultipliers

大面积型光电倍增管(Photomultiplier Tube,PMT)广泛应用于各种高能物理实验中,但它对磁场比较敏感,在有地磁场的情况下实验结果的可靠性难以保证。为此,需要在电磁屏蔽间内放置高磁导率磁屏蔽罩定量屏蔽磁场,或在电磁屏蔽室缠绕三围螺线管线圈定量屏蔽地磁场。利用实验虚拟仪器工程平台,基于常用通信协议,建立了一套光电倍增管磁场效应在线测试系统,实现对光斑尺寸和磁场强度的自动调节,光电倍增管阳极信号的实时采集、存储和显示,可用于研究光电倍增管的地磁场效应。

[Background] Large area photomultiplier tubes （PMTs） have been increasingly applied to high energy physics experiments, reliable results of PMTs＇ parameters may not be obtained without earth-magnetic （EM） shielding. [Purpose] This study aims to build a test system for EM effect of PMT and obtain its properties in different magnetic field intensity. [Methods] Based on the current PMT performance testing system, high-permeability material is used to qualitatively shield the magnetic field; and the EM shielded room entwined with solenoid coil is used to quantitatively shield the magnetic field. Based on the RS-232, universal serial bus （USB） and local area network （LAN） interface communication protocols, test software is developed in LabVIEW. [Results ＆ Conclusion] The high voltage supply, light source intensity, magnet strength can be remotely automatically adjusted. And anode signal of PMT is real-time sampled and stored. It is helpful for studying earth-magnetic effect of large-area photomultipliers with this system.