Construction and On-site Performance of the LHAASO WFCTA Camera

TL;DR

This paper details the design, manufacturing, and testing of SiPM-based cameras for the LHAASO WFCTA, demonstrating their effective performance under moonlight for cosmic ray detection.

Contribution

It introduces the development and testing of 18 SiPM-based cameras with light funnels for the WFCTA, highlighting their capabilities and challenges in a high-altitude observatory.

Findings

Cameras operate effectively under moonlight conditions.

Successful collection of over 100 million cosmic ray events.

Identified challenges in dynamic range and dark count rate.

Abstract

The focal plane camera is the core component of the Wide Field-of-view Cherenkov/fluorescence Telescope Array (WFCTA) of the Large High-Altitude Air Shower Observatory (LHAASO). Because of the capability of working under moonlight without aging, silicon photomultipliers (SiPM) have been proven to be not only an alternative but also an improvement to conventional photomultiplier tubes (PMT) in this application. Eighteen SiPM-based cameras with square light funnels have been built for WFCTA. The telescopes have collected more than 100 million cosmic ray events and preliminary results indicate that these cameras are capable of working under moonlight. The characteristics of the light funnels and SiPMs pose challenges (e.g. dynamic range, dark count rate, assembly techniques). In this paper, we present the design features, manufacturing techniques and performances of these cameras. Finally, the test facilities, the test methods and results of SiPMs in the cameras are reported here.