远距离大动态范围电荷测量电路的设计

Design of long-distance and large-dynamic-range of charge measurement circuit

介绍了大型高海拔空气簇射观测站(Large High Altitude Air Shower Observatory,LHAASO)空气簇射芯探测器阵列(Shower core detector array,SCDA)读出电子学方案的预研设计。系统采用基于电荷积分法的电荷测量方案,读出电子学通过同轴电缆接收光电倍增管输出的电流信号;采用在输入端与电荷积分放大器的虚地点之间接入等效50?电阻的终端阻抗匹配方案,并通过Pspice仿真验证该阻抗匹配的可行性。电路测试结果表明,该电路能满足远距离10 bit大动态范围电荷测量的设计指标要求。

Background： The air shower core detector array （SCDA） is one of the important detectors to be constructed at the heart of the KM2A （one kilometer square extensive air shower array） with the area of 5 000 m2, in large high altitude air shower observatory （LHAASO）. Purpose： This study aims to design the readout electronics of SCDA for accurate charge measurement of the input photomultiplier tube （PMT） signal for three orders of magnitude. Methods： A 50-Ω impedance match between the ＂virtual＂ grounding and input end is employed to measure the charge by the charge integration method. The feasibility of impedance match is verified by ＂Pspice＂ simulation tool. The output current signal from the PMT is collected and processed by the readout electronics of charge integration circuit via coaxial cable. Results： The performance testing in the laboratory shows that the designed circuit satisfies design requirements of the long-distance and large-dynamic-range charge measurement. Conclusion： The simulation and testing of ＂virtual＂ grounding impedance match validate the feasibility of this circuit. The readout electronics fulfills the application requirements of SCDA.