An Analogue Front-End ASIC Prototype Designed For PMT Signal Readout

TL;DR

This paper presents a prototype ASIC designed for precise time and charge measurement of PMT signals in high-energy gamma ray detection, demonstrating high resolution, low crosstalk, and temperature stability for large-scale observatories.

Contribution

The paper introduces a novel analogue front-end ASIC specifically designed for PMT readout in large water Cherenkov detectors, with improved resolution and stability features.

Findings

Time resolution better than 350 ps

Charge resolution better than 10% at 1 P.E.

Low channel crosstalk and temperature dependency

Abstract

The Large High Altitude Air Shower Observatory (LHAASO) is designed for high energy gamma ray and cosmic ray detection. A Water Cherenkov Detector Array which is sensitive to gamma ray showers above a few hundred GeV is proposed to survey gamma ray sources. The WCDA consists of 3600 PhotoMultiplier Tubes (PMT) which collect the Cherenkov light produced by the shower particles in water. Both high precision time and charge measurement are required over a large dynamic range from 1 photo electron (P.E.) to 4000 P.E. Prototype of an analogue front-end Application Specific Integrated Circuit (ASIC) fabricated in Chartered 0.35 {\mu}m CMOS technology is designed to read out PMT signal in the WCDA. This ASIC employs leading edge discrimination and RC4 shaping structure; combined with the following Time-to-Digital Converter (TDC) and Analog-to-Digital Converter (ADC), both the arrival time and charge of the PMT signal can be measured. Initial test results indicate that time resolution is better than 350 ps and charge resolution is better than 10% at 1 P.E. and better than 1% with large input signals (300 P.E. to 4000 P.E.). Besides, this ASIC has a small channel-to-channel crosstalk and low ambient temperature dependency.