Dielectric-Boosted Sensitivity to Cylindrical Azimuthally Varying Transverse-Magnetic Resonant Modes in an Axion Haloscope

TL;DR

This paper introduces a novel dielectric-boosted resonator design that enhances sensitivity to high-mass axions in haloscope experiments by enabling azimuthally varying TM modes to become axion-sensitive.

Contribution

The study proposes and demonstrates a new cavity design using dielectric wedges to make azimuthally varying TM modes sensitive to axions, improving detection prospects for high-mass axions.

Findings

Finite-element modelling shows increased axion sensitivity with dielectric wedges.

Experimental results confirm the predicted enhancement over traditional cavities.

Design is promising for high-mass axion searches above 60 μeV.

Abstract

Axions are a popular dark matter candidate which are often searched for in experiments known as ``haloscopes" which exploit a putative axion-photon coupling. These experiments typically rely on Transverse Magnetic (TM) modes in resonant cavities to capture and detect photons generated via axion conversion. We present a study of a resonant cavity design for application in haloscope searches, of particular use in the push to higher mass axion searches (above $\sim$60$\,\mu$eV). In particular, we take advantage of azimuthally varying TM$_{m10}$ modes which, whilst typically insensitive to axions due to field non-uniformity, can be made axion-sensitive (and frequency tunable) through strategic placement of dielectric wedges, becoming a type of resonator known as a Dielectric Boosted Axion Sensitivity (DBAS) resonator. Results from finite-element modelling are presented, and compared with a simple proof-of-concept experiment. The results show a significant increase in axion sensitivity for these DBAS resonators over their empty cavity counterparts, and high potential for application in high mass axion searches when benchmarked against simpler, more traditional designs relying on fundamental TM modes.