Hunting for the Axion: Innovating Cavity Geometry for Large-Volume, High-Frequency Dark Matter Searches (ADMX-VERA)

The QCD axion is a promising dark matter candidate, originally proposed by particle physicists  as a solution to the strong CP problem.  At frequencies higher than a few GHz, it is difficult to reach theoretical benchmarks, as the scan rate falls off rapidly with increased frequency due to the detector's volume reduction.  “Axion Dark Matter eXperiment - Volume Enhanced Resonators for Axions” (ADMX-VERA) explores new volume enhancing geometries that allow for high-volume cavities (V>>λ³) while maintaining high frequency resonance.

In this talk I will focus on a “tunable wedge” design for VERA.  We have demonstrated its feasibility by characterizing the 7-8 GHz “single wedge” and are about to launch a cryogenic Dark-Photon search in a dilution refrigerator.  Expanding the design to multiple wedges allows access to higher frequencies with a high volume.  I will present the design features of a “triple wedge” cavity and present test results between 9-11 GHz.  This cavity has a volume of V=171λ³, orders of magnitude larger than a cylindrical cavity.

The VERA group’s long term goal is to develop similar tunable resonators in the 4-30 GHz range, making good use of a V~m³ solenoid magnet.  In conjunction with a coordinated effort to develop photon counting detectors (SMPD), VERA will be able to reach the DFSZ benchmark over this entire frequency range