Phonon Mediated Microwave Kinetic Inductance Detectors

We are developing athermal-phonon mediated particle detectors using microwave kinetic inductance detectors (MKIDs) as the phonon sensing elements. Since MKIDs are easily multiplexed, hundreds of sensors patterned on a single dielectric substrate can be read out simultaneously, leading to a precise, time-resolved measurement of the phonon flux at each point on the detector surface. In addition to providing a high-resolution measurement of the location of the interaction, the energy deposited by the particle can be reconstructed with an expected baseline resolution of tens of eV. The complexity of the cryogenic readout electronics is significantly reduced relative to designs based on multiplexed transition edge sensors (TES). Initial proof-of-principle devices demonstrate energy resolutions as good as 0.7 keV at 30 keV, dominated by the position dependence of the phonon signal. New designs are aimed at improving this resolution by more than an order of magnitude. Such high-resolution phonon mediated detectors would have applications including direct detection of dark matter, hard X-ray/soft gamma-ray astrophysics, neutrinoless double beta decay, and coherent neutrino-nucleus scattering.