Hybrid Phonon-Mediated High-Voltage Detectors for WIMP Search and Coherent Neutrino Scattering Experiments
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We propose to perform Detector R&D to develop an improved ultra-low threshold detector technology that may allow discoveries in coherent scattering of Weakly Interacting Massive Particles (WIMPs) as well as similar Coherent Elastic Neutrino Nucleus Scattering (CENNS) of low energy solar and reactor neutrinos. The same detector technology that is driving the field of low-mass WIMP search is also at the forefront of searches for Beyond Standard Model (BSM) physics using reactor neutrinos, such as Sterile Neutrino search, Non-Standard Interactions (NSI) and searches for Z' using the CENNS process as a precision probe. Due to the low energy recoils expected from WIMPs and CENNS, the primary challenge is the availability of large mass detectors (~kg) with low energy thresholds (sub-keV). With a 3-year funding (for DE-SC0017859) from the Detector R&D frontier, we have developed a low-threshold hybrid detector technology that allows for detection of nuclear recoil events (signal) in cryogenic silicon detectors, while providing event by event discrimination against electron recoil events (background). This monolithic detector combines two distinct technologies we develop for the SuperCDMS dark matter search experiment. Interleaved Z-sensitive Ionization Phonon (iZIP) detector that provides event by event discrimination by measuring both ionization and phonon energies from particle interaction inside cryogenic germanium and silicon detectors. However, this discrimination is lost below a keV of recoil energy due to the dominant ionization noise combined with suppressed ionization yield for the signal nuclear recoil events. High Voltage (HV) detectors provide a straight forward path to low recoil energies by utilizing the Neganov-Trofimov-Luke amplification whereby the low ionization signal is amplified into high phonon signals. However, this technique results in the loss of event electron recoil and nuclear recoil discrimination that is available with iZIP detector at higher energies (few keV). We have carried out the first demonstration of a phonon-mediated cryogenic silicon detector technology that provides primary phonon measurement in a low-voltage region, and a simultaneous measurement of the ionization signal through Neganov-Trofimov-Luke amplification in a high voltage region, both in a monolithic two-stage detector..............
