Split-cavity tuning of a rectangular axion haloscope operating around 8.4 GHz

TL;DR

This paper introduces a purely mechanical cavity tuning method for axion haloscopes operating around 8.4 GHz, achieving significant tuning range with minimal quality factor loss, enhancing dark matter detection capabilities.

Contribution

A novel mechanical tuning technique for axion haloscopes that avoids dielectrics and maintains high quality factors over a broad frequency range.

Findings

Achieved ~600 MHz tuning range with less than 20% Q factor reduction.

Demonstrated effective tuning at both room and cryogenic temperatures.

Proposed improvements for larger tuning ranges with better alignment mechanisms.

Abstract

The axion haloscope is the currently most sensitive method to probe the vanishingly small coupling of this prominent Dark Matter candidate to photons. To scan a sizeable axion Dark Matter parameter space, the cavities that make up the haloscope need to be tuned efficiently. In this article, we describe a novel technique to tune axion haloscopes around $8.4$~GHz in a purely mechanical manner without the use of dielectrics. We achieve tuning by introducing a gap along the cavity geometry. A quality factor reduction of less than 20\% is achieved experimentally for a tuning range of around 600~MHz at room temperature and at cryogenic temperatures for around 300~MHz. A larger tuning range would require an improved alignments mechanism. We present the results of a corresponding prototype and outline prospects to further develop this technique.