A Symmetric Multi-rod Tunable Microwave Cavity for the HAYSTAC Dark Matter Axion Search

TL;DR

This paper presents a novel symmetric multi-rod microwave cavity design for the HAYSTAC axion search, optimized for high frequencies (5.5-7.4 GHz) with high symmetry, quality factor, and tunability.

Contribution

The paper introduces a new cavity design with a symmetric multi-rod structure that enhances tuning and performance for axion searches at high frequencies.

Findings

Designed a high-frequency cavity covering 5.5-7.4 GHz

Achieved high symmetry and tunability in the cavity

Discussed design evolution and future challenges

Abstract

The microwave cavity experiment is the most sensitive way of looking for axions in the 0.1-10 GHz range, corresponding to masses of 0.5 - 40 $\mu$eV. The particular challenge for frequencies greater than 5 GHz is designing a cavity with a large volume that contains a resonant mode that has a high form factor, a high quality factor, a wide dynamic range, and is free from intruder modes. For HAYSTAC, we have designed and constructed an optimized high frequency cavity with a tuning mechanism that preserves a high degree of rotational symmetry, critical to maximizing its figure of merit. This cavity covers an important frequency range according to recent theoretical estimates for the axion mass, 5.5 - 7.4 GHz, and the design appears extendable to higher frequencies as well. This paper will discuss key design and construction details of the cavity, present a summary of the design evolution, and alert practitioners of potentially unfruitful avenues for future work.