Reflectivity of VUV-sensitive Silicon Photomultipliers in Liquid Xenon

TL;DR

This study measures the reflectivity of various silicon photomultipliers and related samples in liquid xenon at VUV wavelengths, providing data crucial for optimizing detector light response in particle physics experiments.

Contribution

It presents the first systematic, angle-resolved reflectivity measurements of SiPMs and related samples immersed in liquid xenon at VUV wavelengths.

Findings

Reflectivity ranges from 25% to 36% at 20° incidence.

Reflectivity increases up to 65% at 70° incidence.

Hamamatsu VUV4 SiPM shows decreasing reflectivity with angle.

Abstract

Silicon photomultipliers are regarded as a very promising technology for next-generation, cutting-edge detectors for low-background experiments in particle physics. This work presents systematic reflectivity studies of Silicon Photomultipliers (SiPM) and other samples in liquid xenon at vacuum ultraviolet (VUV) wavelengths. A dedicated setup at the University of M\"unster has been used that allows to acquire angle-resolved reflection measurements of various samples immersed in liquid xenon with 0.45{\deg} angular resolution. Four samples are investigated in this work: one Hamamatsu VUV4 SiPM, one FBK VUV-HD SiPM, one FBK wafer sample and one Large-Area Avalanche Photodiode (LA-APD) from EXO-200. The reflectivity is determined to be 25-36% at an angle of incidence of 20{\deg} for the four samples and increases to up to 65% at 70{\deg} for the LA-APD and the FBK samples. The Hamamatsu VUV4 SiPM shows a decline with increasing angle of incidence. The reflectivity results will be incorporated in upcoming light response simulations of the nEXO detector.