Improving Performance of a Multiplexed Dark Matter Detector via Infrared Isolation

Abstract

Microwave Kinetic Inductance Detectors (MKIDs) are superconducting microresonators that are most commonly used for microwave detection in astronomy. They have potential for use as phonon detectors in cryogenic dark matter searches, but their implementation faces a number of technical challenges. Among these issues is the potential for higher-temperature infrared photons to reach the superconducting substrate and consequently degrade the quality factor of the MKID’s resonance. This thesis details the design and construction of epoxy-based filters meant to mitigate this effect, and finds that their installation in the readout system for an Al MKID increased its quality factor by an average of 12% across a range of operating temperatures and powers.