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

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.

Automated summary

A novel high-brightness atomic beam comprised of a two-body exotic atom called muonium (M = mu(+) + e(-)) is being developed for atomic physics and gravitational interaction measurements. The use of silicon photomultipliers (SiPMs) at ultra-low temperatures in superfluid helium targets for detection is demonstrated. Single photon detection with SiPMs below 0.85 K is shown to be feasible. Additionally, segmented scintillation detectors have been developed.