High-Q superconducting LC-resonator for DMRadio

DMRadio aims to search for low-mass axions using a lumped-element resonator. Optimal resonator technology is critical to reach the required sensitivity. We present a new superconducting lumped-element resonator operating at a fixed frequency of 250 kHz with an unprecedented quality factor of Q=2x10⁶ at cryogenic temperatures. We will describe the design and provide practical recipes for constructing such a resonator. The achieved performance informs the resonator design for DMRadio-50L and paves the way toward an ambitious GUT-scale experiment.