Scintillation detectors with silicon photomultiplier readout in a dilution refrigerator at temperatures down to 0.2 K

TL;DR

This paper demonstrates the operation of silicon photomultipliers at ultra-low temperatures in superfluid helium, enabling segmented scintillation detectors for atomic physics experiments involving muonium at millikelvin temperatures.

Contribution

It provides the first characterization of SiPMs at temperatures below 1 K and develops segmented scintillation detectors suitable for ultra-cold atomic physics applications.

Findings

SiPMs can detect single photons below 0.85 K in superfluid helium.

Segmented scintillation detectors were successfully operated at 1.7 K and 170 mK.

The temperature dependence of SiPM signal properties was characterized.

Abstract

We are developing a novel high-brightness atomic beam, comprised of a two-body exotic atom called muonium (M $ = \mu^+ + e^-$), for next-generation atomic physics and gravitational interaction measurements. This M source originates from a thin sheet of superfluid helium (SFHe), hence diagnostics and later measurements require a detection system which is operational in a dilution cryostat at temperatures below 1 K. In this paper, we describe the operation and characterization of silicon photomultipliers (SiPMs) at ultra-low temperatures in SFHe targets. We show the temperature dependence of the signal shape, breakdown voltage, and single photon detection efficiency, concluding that single photon detection with SiPMs below 0.85 K is feasible. Furthermore, we show the development of segmented scintillation detectors, where 16 channels at 1.7 K and one channel at 170 mK were commissioned using a muon beam.