A tunable clamshell cavity for wavelike dark matter searches

Abstract

Here, we present a frequency tuning mechanism for microwave cavities designed for axion dark matter searches and show that it provides a range of at least 200 MHz for the fundamental mode TM010 resonant at ∼10 GHz. The apparatus is based on a clamshell cavity, with the two semi-cells held together at a fixed joint while the other side opens to tune the frequency of the resonant modes. Measurements of the cavity frequencies and quality factor were taken at liquid helium temperature as the aperture was increased incrementally to ∼2°. We show that the frequency shift is approximately linear with respect to the angle of aperture with no mode crossings present for an aperture less than 2°. Furthermore, the form factor and quality factor of the TM010 mode remain relatively constant throughout the tuning as predicted by simulation.