Coherent elastic neutrino-nucleus scattering (CEνNS) represents a powerful probe for low-energy neutrino physics. In this work, we present a novel cryogenic detection scheme utilizing pure CsI crystals coupled with silicon photomultiplier (SiPM) readout. While previous experiments have demonstrated the viability of this detector architecture at liquid-nitrogen temperatures (77 K), theoretical models anticipate significant performance enhancements at deeper cryogenic temperatures. To systematically investigate this regime, we developed a custom-built cryogenic facility with continuous temperature regulation from 30 K to 293 K. Building upon prior single-photon calibrations of the SiPMs at 40 K, we characterized the pure CsI detection system using 13.9–59.54 keV X/γ-rays and 5.5 MeV α-particles. Crucially, we report the observation of a pronounced anti-quenching phenomenon. At 35 K, the scintillation light yield for densely ionizing α-particles reaches 19.2 p.e./keV, unambiguously exceeding the 17.3 p.e./keV measured for electron recoils induced by γ-rays. Because the ionization density profiles of α-particles closely emulate those of low-energy nuclear recoils generated via CEνNS, this enhanced light yield for high linear energy transfer (LET) interactions is of paramount importance for validating the reliability of this technique. This cryogenic pure CsI platform offers a transformative pathway for achieving the ultra-low thresholds required in next-generation reactor CEνNS experiments.
Doppler broadening positron annihilation spectroscopy is a powerful technique for investigation of neutral and negatively-charged atomic-scale defects in materials. However, it has one important drawback, which is that studies are typically designed to only illuminate relative differences in positron annihilation characteristics in a specific suite of samples. It is difficult and considered ill-advised to compare the data that different laboratories report for apparently similar samples, which limits the scope of applications of the technique. The root of the problem is that the resolution and calibration of the detector used to collect the energy spectra of the positron-electron annihilation radiation affect their shape and the S and W parameters that are used for its characterisation. The present study explores whether this obstacle can be overcome by modelling the differences between the data sets that were obtained via different detectors or the same detector at different times. We were able to reproduce the observed differences between the analyses of UO2 that were acquired in our laboratory over the past ∼25 years using the same detector that has changed its properties. However, our attempt to reproduce the differences between our and literature data did not work out as well, which can be pinned in part to a real difference between the samples and in part to the incompleteness of the published descriptions of the methodology. We conclude with recommendations to improve current practices of data acquisition and reporting.
