LHAASO-WFCTA读出电子学系统架构设计

The design of framework for readout electronics of LHAASO-WFCTA

摘要:

广角切伦科夫望远镜阵列（Wide Field of View Cherenkov Telescope Array，WFCTA）是大型高海拔空气簇射观测站（Large High Altitude Air Shower Observatory，LHAASO）的主要探测器阵列之一，其物理目标是完成30 TeV到几个EeV的宇宙线能谱测量. 望远镜读出电子学系统包括1 024个通道，需要处理的信号既有脉宽为几十ns的切伦科夫信号，又有脉宽为μs的荧光信号. 本文详细介绍了望远镜读出电子学系统的架构设计，为了减少数据量，设计了在线触发的事例筛选架构：在子模块电子学上先进行第一级硬件触发，再在触发电路上实现事例触发. 同时该电子学系统采用了4点压缩的方式获取波形数据，覆盖波形宽度为2.24 μs. 实验室测试结果表明：读出电子学系统可以正确获取信号波形，电荷测量的动态范围可以覆盖10 P.E.(Photon Electron)到32 143 P.E.，高增益通道和低增益通道的重叠区从857 P.E.到1 714 P.E.，高低增益比值与设计相符，电荷分辨率在10 P.E.时优于20%，在32 000 P.E.时优于5%，相对偏差在10 P.E.时优于5%，在32 000 P.E.时优于2%，该读出电子学系统满足设计要求.

Abstract:

Wide Field of View Cherenkov Telescope Array (WFCTA) is one of the main detector arrays in the Large High Altitude Air Shower Observatory (LHAASO). Its physical goal is to measure the cosmic ray energy spectrum from 30 TeV to several EeV. The telescope readout electronics system consists of 1024 channels and the signals to be processed include both Cherenkov signals with pulse widths of tens of ns and fluorescence signals with pulse widths of μs. This paper describes the framework design of the telescope readout electronics system in detail. In order to reduce the amount of data, an online trigger is designed, that is to say, the first-level hardware trigger is performed on the subcluster electronics, and then the event trigger is implemented on the trigger circuit. At the same time, the electronic system uses a 4-point compression method to obtain waveform data, covering a waveform width of 2.24 μs. The laboratory test results show that the readout electronics system can correctly obtain the signal waveform, and the dynamic range of the charge measurement can cover 10 P.E. (Photon Electron) to 32 143 P.E. The overlap area of the high gain channel and the low gain channel is from 857 P.E. to 1 714 P.E., and the high-low gain ratio is consistent with the design. The charge resolution is better than 20% at 10 P.E., better than 5% at 32 000 P.E., and the relative deviation is better than 5% at 10 P.E., and better than 2% at 32 000 P.E, and thus readout electronics system meets design requirements.