Response to nuclear recoil of the undoped CsI at cryogenic temperature

In this study, we have focused on enhancing our understanding of nuclear recoil responses in undoped CsI detector technology, following the COHERENT collaboration's detection of Coherent Elastic Neutrino-Nucleus Scattering (CEvNS) using a CsI[Na] detector. A primary limitation in the original setup was the Cherenkov radiation background from the quartz window of the PMT. To mitigate this, we considered transitioning to SiPM arrays, which lack a quartz window.



Central to our investigation is the behavior of undoped CsI crystals at cryogenic temperatures. This shift is necessitated by SiPMs' requirement for cryogenic operating temperatures to reduce their high dark count rate at room temperature. Notably, undoped CsI demonstrates a significantly higher light yield at 40 Kelvin than its doped counterpart at 300 Kelvin.



The key aspect of our research was conducted at the Triangle Universities Nuclear Laboratory (TUNL), where we measured the Quenching Factor of undoped CsI at 77 K. This measurement is crucial for understanding the response of the detector to nuclear recoil energies. Our findings indicated a quenching factor ranging from 13-18% for nuclear recoil energies between 8.9-51.7 keV in cryogenic CsI (CryoCsI). We will present the experiment and analysis details.