Development of a Cryogenic Hybrid Detector for Rare-Event Searches via Simultaneous Phonon and Photon Readout

Silicon photomultipliers (SiPMs) provide compact, low-noise photon detection well suited for rare-event searches at cryogenic temperatures. We present a systematic study of SiPM-coupled scintillation detectors (undoped and doped CsI, sapphire, and GaAs) as prototypes for future cryogenic rare-event experiments. The detector response was characterized under gamma irradiation to probe electron-recoil events over temperatures ranging from 100 K to room temperature using a cryostat and optimum operating range for each crystal was identified for photon detection efficiency. Pulse-shape analysis reveals a pronounced temperature dependence in scintillation decay components. 

We are exploring simultaneous measurement of photons and phonons from these scintillating crystals using a hybrid system where the crystal is kept at a few mK temperature for phonon measurement through tungsten TESs and the light is transferred to SiPM operating at higher than 100K temperature. Simultaneous measurement of phonon and photon may allow event by event discrimination between electron recoil background and nuclear recoil signal events. We will also explore pulse shape based electron recoil and nuclear recoil discrimination.