Measurements of Cherenkov Photons with Silicon Photomultipliers

TL;DR

This paper evaluates Silicon Photomultipliers (SiPMs) in Cherenkov detectors, demonstrating their advantages over traditional photomultiplier tubes in high magnetic fields and showing improved photon detection and light yield.

Contribution

It presents the first comparative study of SiPMs versus PMTs in Cherenkov detectors under cosmic-ray and electron beam conditions, highlighting their potential for particle identification upgrades.

Findings

SiPMs outperform PMTs in photon detection rates

Light guides significantly increase light yield

Dark noise from false coincidences is estimated

Abstract

A novel photon detector, the Silicon Photomultiplier (SiPM), has been tested in proximity focusing Ring Imaging Cherenkov (RICH) counters that were exposed to cosmic-ray particles in Ljubljana, and a 2 GeV electron beam at the KEK research facility. This type of RICH detector is a candidate for the particle identification detector upgrade of the BELLE detector at the KEK B-factory, for which the use of SiPMs, microchannel plate photomultiplier tubes or hybrid avalanche photodetectors, rather than traditional Photomultiplier Tubes (PMTs) is essential due to the presence of high magnetic fields. In both experiments, SiPMs are found to compare favourably with PMTs, with higher photon detection rates per unit area. Through the use of hemispherical and truncated pyramid light guides to concentrate photons onto the active surface area, the light yield increases significantly. An estimate of the contribution to dark noise from false coincidences between SiPMs in an array is also presented.