Performance of a phonon-mediated detector using KIDs optimized for sub-GeV dark matter

TL;DR

This paper reports on a phonon-mediated KID detector optimized for sub-GeV dark matter detection, achieving sub-eV energy thresholds through design improvements and quantum-limited amplification.

Contribution

It introduces a KID-based detector with improved energy resolution and a clear pathway to sub-eV thresholds for dark matter searches.

Findings

Current device achieves 6 eV resolution on resonator energy

Projected 5 eV baseline resolution after noise mitigation

Path to sub-eV thresholds with quantum-limited amplifiers

Abstract

Detection of sub-GeV dark matter candidates requires sub-keV detector thresholds on deposited energy. We provide an update on a gram-scale phonon-mediated KID-based device that was designed for a dark matter search in this mass range at the Northwestern Experimental Underground Site. Currently, the device is demonstrating 6 eV resolution on the energy absorbed by the resonator. With some important assumptions, this translates to 20 eV baseline resolution on energy deposited in the substrate. We show that TLS noise dominates this energy resolution estimate. After modifying the design to mitigate TLS noise, we project 5 eV baseline resolution on energy deposited in the substrate (1.5 eV on energy absorbed by the resonator) for an amplifier-white-noise-dominated device. Finally, we present a clear path forward to sub-eV thresholds, which includes installation of a quantum-limited superconducting parametric amplifier and adjustments to the material makeup of our resonators.