Large-Area MPPC with Enhanced VUV Sensitivity for Liquid Xenon Scintillation Detector

TL;DR

This paper reports the development and testing of a large-area VUV-sensitive MPPC for liquid xenon scintillation detection, achieving high PDE and suitable performance for high-rate experiments in particle physics.

Contribution

It introduces a novel large-area VUV-MPPC with enhanced VUV sensitivity and optimized design for liquid xenon detectors, enabling improved photon detection in high-rate environments.

Findings

High photon detection efficiency up to 21% in VUV range

Successful performance tests of 4180 VUV-MPPCs at room temperature

Large active area achieved by connecting multiple small chips

Abstract

A large-area Multi-Pixel Photon Counter (MPPC) sensitive to vacuum ultra violet (VUV) light has been developed for the liquid xenon (LXe) scintillation detector of the MEG II experiment. The LXe detector is designed to detect the 52.8\,MeV photon from the lepton flavour violating decay $\mu^+ \to \mathrm{e}^+ \gamma$ and is based on $900\,\ell$ LXe with a highly granular scintillation readout by 4092 VUV-MPPCs with an active area of $139\,\mathrm{mm}^2$ each, totalling $0.57\,\mathrm{m}^2$. The VUV-MPPC shows an excellent performance in LXe, which includes a high photon detection efficiency (PDE) up to 21\% for the LXe scintillation light in the VUV range, a high gain, a low probability of the optical cross-talk and the after-pulsing, a low dark count rate and a good single photoelectron resolution. The large active area of the VUV-MPPC is formed by connecting four independent small VUV-MPPC chips in series to avoid the increase of the sensor capacitance and thus, to have a short pulse-decay-time, which is crucial for high rate experiments. Performance tests of 4180 VUV-MPPCs produced for the LXe detector were also carried out at room temperature prior to the installation to the detector and all of them with only a few exceptions were found to work properly. The design and performance of the VUV-MPPC are described in detail as well as the results from the performance tests at room temperature.