Characterization of SiPMs at 40 K for neutrino coherent detection based on pure CsI

TL;DR

This work addresses the challenge of deploying SiPMs for coherent neutrino detection with pure CsI at deep cryogenic temperatures by building a 30–293 K adjustable cryogenic system and evaluating three SiPM types. Using ROOT-based analysis of SPE spectra, the study maps how gain, $V_{bd}$, DCR, after-pulse, iCT, and SPE resolution evolve with temperature and overvoltage, identifying a favorable 40 K operating regime. Key findings include a multi-order reduction in DCR at low temperatures, device-dependent linearity of $V_{bd}$ with temperature above 77 K, and optimal overvoltages that maximize SPE resolution while minimizing noise; Broadcom devices offer the best overall performance at 40 K. These results provide essential technical groundwork for reliable light-yield measurements in low-temperature CsI detectors, enabling improved sensitivity for neutrino experiments such as CEνNS.

Abstract

Silicon photomultiplier (SiPM), as the core photoelectric sensor for coherent neutrino detection in low-temperature pure CsI, its working performance directly determines the measurement accuracy of the scintillator light yield. Our previous research has fully demonstrated the performance of pure CsI at liquid nitrogen temperature. More intriguingly, its performance is expected to be even better at 40 K. However, the performance characteristics of SiPM in the 40 K temperature range still remain to be explored. In this study, a self-developed adjustable temperature control system ranging from 30 K to 293 K was built to investigate the key performance parameters of SiPM at different temperatures, such as single photoelectron spectrum, gain, breakdown voltage, dark count rate, after-pulse, internal crosstalk, and single photoelectron resolution. Special emphasis was placed on examining the key performance parameters of SiPM in the 40 K temperature range to evaluate its feasibility for light yield measurement in this temperature range. The results show that this study obtained the parameter variation trends and optimal working conditions of 3 types of SiPM at different temperatures, thereby improving the sensitivity of the detector. This research provides important technical support for low-temperature detection in neutrino physics experiments.

Figures (13)

• Figure 1: The left figure is a physical diagram. The right figure annotates the placement methods of the cold head, cold plate, and SiPM. Apiezon N-type vacuum grease is applied between the SiPM and the cold plate to ensure more uniform heat distribution. SiPMs of the same model are symmetrically installed on both sides of the cold plate. Through dual-channel data comparison, the accuracy of experimental results is improved, and single-point measurement errors are reduced.
• Figure 2: Schematic diagram of SiPM low-temperature readout.
• Figure 3: SiPM and preamplifier. The top-left image shows the preamplifier with a gain of 10×. The top-right image shows the 4 × 4 array SiPM developed by Hamamatsu, with each chip measuring 6 mm × 6 mm. The bottom-left image shows the 2 × 1 dual-chip SiPM developed by Broadcom, with each chip measuring 6.14 mm × 6.14 mm. The bottom-right image shows the monolithic SiPM developed by NDL, with dimensions of 6.24 mm × 6.24 mm.
• Figure 4: The figure above shows the single-photon, two-photon, and after-pulse waveforms of Hamamatsu SiPM at 40 K and a voltage of 36.5 V.
• Figure 5: The figure above shows the energy spectrum of Hamamatsu SiPM at 40 K and a voltage of 36.5 V.