Evaluation of a front-end ASIC for the readout of PMTs in large dynamic range

TL;DR

This paper evaluates a specialized ASIC designed for reading out PMT signals in the LHAASO project's WCDA, demonstrating high precision, stability, and suitability for large dynamic range applications in cosmic ray detection.

Contribution

The paper presents the development and comprehensive performance evaluation of a new QTC ASIC tailored for PMT readout in large-scale cosmic ray observatories.

Findings

Time resolution better than 400 ps

Charge resolution better than 1% for large signals

Stable performance across temperature and input rates

Abstract

The Large High Altitude Air Shower Observatory (LHAASO) project has been proposed for the survey and study of cosmic rays. In the LHAASO project, the Water Cherenkov Detector Array (WCDA) is one of major detectors for searching gamma ray sources. A Charge-to-Time Convertor (QTC) ASIC (Application Specification Integrated Circuit) fabricated in Global Foundry 0.35 {\mu}m CMOS technology, has been developed for readout of Photomultiplier Tubes (PMTs) in the WCDA. This paper focuses on the evaluation of this front-end readout ASIC performance. Test results indicate that the time resolution is better than 400 ps and the charge resolution is better than 1% with large input signals and remains better than 15% @ 1 Photo Electron (P.E.), both beyond the application requirement. Moreover, this ASIC has a weak ambient temperature dependence, low input rate dependence and high channel-to-channel isolation.