Progress in Readout Electronics for STCF ECAL

The Super Tau-Charm Facility (STCF) is a significant initiative for accelerator-based particle physics in China. Electromagnetic calorimeter (ECAL) is one of the important detectors of STCF, which is tasked with the precise measurement of photons. STCF ECAL uses pure cesium iodide (pCsI) crystals and large-area avalanche photodiodes (APDs) for scintillation and photoelectric conversion. This article explores the methods for energy and time measurement, as well as signal processing under high event rates. The readout electronics scheme, which combines a charge-sensitive amplifier (CSA) with a waveform fitting algorithm after analog-to-digital conversion, is experimentally verified. We determined the CSA parameters through simulations to reduce circuit noise and conducted tests with LEDs to simulate background events. Measurements indicate that the energy measurement noise is 0.8 fC, and the time measurement accuracy reaches 300 ps at 1 GeV.