Reflectivity and PDE of VUV4 Hamamatsu SiPMs in Liquid Xenon

TL;DR

This study measures the reflectivity and PDE of VUV4 SiPMs in liquid xenon at 175 nm, revealing their angular dependence and providing crucial data for noble liquid gas detectors in particle physics experiments.

Contribution

First measurement of angular dependence of reflectivity and PDE of VUV4 SiPMs in liquid xenon at 175 nm, aiding detector optimization.

Findings

Reflectivity around 30% at 15° incidence.

PDE varies within ±8% among devices.

Both reflectivity and PDE decrease with increasing incident angle.

Abstract

Understanding reflective properties of materials and photodetection efficiency (PDE) of photodetectors is important for optimizing energy resolution and sensitivity of the next generation neutrinoless double beta decay, direct detection dark matter, and neutrino oscillation experiments that will use noble liquid gases, such as nEXO, DARWIN, DarkSide-20k, and DUNE. Little information is currently available about reflectivity and PDE in liquid noble gases, because such measurements are difficult to conduct in a cryogenic environment and at short enough wavelengths. Here we report a measurement of specular reflectivity and relative PDE of Hamamatsu VUV4 silicon photomultipliers (SiPMs) with 50 micrometer micro-cells conducted with xenon scintillation light (~175 nm) in liquid xenon. The specular reflectivity at 15 deg. incidence of three samples of VUV4 SiPMs is found to be 30.4+/-1.4%, 28.6+/-1.3%, and 28.0+/-1.3%, respectively. The PDE at normal incidence differs by +/-8% (standard deviation) among the three devices. The angular dependence of the reflectivity and PDE was also measured for one of the SiPMs. Both the reflectivity and PDE decrease as the angle of incidence increases. This is the first measurement of an angular dependence of PDE and reflectivity of a SiPM in liquid xenon.