A Prototype Hybrid Mode Cavity for Heterodyne Axion Detection

TL;DR

This paper presents a prototype hybrid cavity designed for heterodyne axion detection, featuring mode tuning and noise suppression, with potential to significantly improve sensitivity in axion searches.

Contribution

The paper introduces a novel hybrid cavity design optimized for heterodyne axion detection, including fabrication, characterization, and tuning mechanisms.

Findings

Cavity supports linearly polarized hybrid modes that maximize signal power.

Tuning mechanism allows 4 MHz frequency scan with minimal cross-coupling noise.

Superconducting version could surpass current astrophysical bounds.

Abstract

In the heterodyne approach to axion detection, axion dark matter induces transitions between two modes of a microwave cavity, resulting in a parametrically enhanced signal power. We describe the fabrication and characterization of a prototype normal conducting cavity specifically optimized for heterodyne detection. Corrugations on the cavity walls support linearly polarized hybrid modes which maximize the signal power while strongly suppressing noise. We demonstrate tuning mechanisms which allow one mode's frequency to be scanned across a 4 MHz range, while suppressing cross-coupling noise by at least 80 dB. A future superconducting cavity with identical geometry to our prototype would have the potential to probe orders of magnitude beyond astrophysical bounds.