Design of the readout electronics prototype for LHAASO WCDA

Abstract

In the Large High Altitude Air Shower Observatory (LHAASO), the Water Cherenkov Detector Array (WCDA) is one of the major detectors. The WCDA electronics are responsible for the readout of 3600 Photomultiplier Tubes (PMTs), and a total of 400 Front End Electronics (FEE) modules are required. The main challenges in the WCDA readout electronics design include: precise time and charge measurement over a large dynamic input amplitude range (1 Photo Electron (P.E.) ∼ 4000 P.E.), high quality of clock distribution and automatic clock phase compensation, and high speed data transfer due to the requirement of “triggerless” architecture. In this paper, we present the prototype design of the readout electronics for the LHAASO WCDA. We also conducted tests on the prototype electronics to evaluate the performance. The results indicate that a charge resolution better than 15%@ 1 P.E. and 2%@ 4000 P.E., and a time resolution better than 0.3 ns RMS are successfully achieved over the whole dynamic range, beyond the application requirement.