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Title ImagePublic Abstract


DE-SC0022167: Design of a low-threshold neutrino detector based on cryogenic undoped Csl at the Spallation Neutron Source

Award Status: Active
  • Institution: University of South Dakota, Vermillion, SD
  • DUNS: 929930808
  • Most Recent Award Date: 01/31/2024
  • Number of Support Periods: 3
  • PM: Beckford, Brian
  • Current Budget Period: 04/01/2024 - 03/31/2025
  • Current Project Period: 04/01/2023 - 03/31/2025
  • PI: Liu, Jing
  • Supplement Budget Period: N/A

Public Abstract

We propose to verify the feasibility of using a cryogenic scintillating crystal based neutrino detector at the Spallation Neutron Source (SNS), Oak Ridge National Laboratory, for the detection of low-mass dark matter particles and non-standard neutrino interactions (NSIs), as part of the detector R&D effort of the COHERENT experiment. The main objectives are

  • to establish systems to test cryogenic SiPM arrays + room temperature CMOS-based ASIC readout electronics, 
  • to survey SiPM arrays from various vendors down to 40 K, and
  • to measure nuclear quenching factor (QF) of undoped cryogenic CsI at the Triangle Universities Nuclear Laboratory (TUNL) down to 40 K.

In 2017, the COHERENT collaboration detected neutrinos emitted from the SNS through a long-seeking physics process named coherent elastic neutrino-nucleus scatterings (CEvNS) using a 14 kg CsI(Na) detector. A PMT was used as the light sensor in that detector. A serious background limiting its sensitivity was the Cherenkov radiation emitted from the PMT quartz window by charged particles. A switch from PMTs to SiPM arrays can be used to completely eliminate this background as SiPMs do not have a quartz window. In order to reduce the high dark count rate of SiPMs at room temperature, they need to be cooled, by liquid nitrogen to 77 K for convenience, or by a pulse-tube refrigerator to 40 K for the best light yield. The cryogenic operation calls for undoped crystals instead of doped ones, since the former at around 4077 K have about twice higher light yields than the latter at 300 K. Compared to the original CsI(Na) detector, the combination of the high photon-detection efficiency of SiPMs and the high light yield of undoped crystals, leads to at least an order of magnitude increase of the detectable CEvNS events, given a similar exposure.

Key concepts of the proposed detector technology has been thoroughly verified at 77 K, including the cryogenic SiPM + undoped CsI combination, and the high light yield of the system. The QF has also been measured at 77 K at TUNL. The proposed study will extend the investigation down to 40 K, seeking for the operation temperature that maximize the performance. If successful, this study will be followed by the design of a 10 kg prototype detector operating at the SNS. Its sensitivities to the proposed dark matter and NSI searches have been proven to be very competitive in two published scientific papers and the latest COHERENT SNOWMASS Whitepaper. 

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