Enhanced tunable cavity development for axion dark matter searches using a piezoelectric motor in combination with gears

TL;DR

This paper presents a novel cavity tuning system for axion dark matter searches that combines a piezoelectric motor and gears to achieve a wide tunable frequency range of about 42%, suitable for extreme experimental environments.

Contribution

The study introduces a new cavity tuning mechanism using a piezoelectric motor and gears, enabling a large and heavy tuning rod for wider frequency tuning in axion searches.

Findings

Achieved a 42% tunable frequency range of the cavity.

Demonstrated effective operation in cryogenic, high-magnetic-field, and high vacuum environments.

Enhanced the driving power for large tuning rods without compromising sensitivity.

Abstract

Most search experiments sensitive to quantum chromodynamics (QCD) axion dark matter benefit from microwave cavities, as electromagnetic resonators, that enhance the detectable axion signal power and thus the experimental sensitivity drastically. As the possible axion mass spans multiple orders of magnitude, microwave cavities must be tunable and it is desirable for the cavity to have a tunable frequency range that is as wide as possible. Since the tunable frequency range generally increases as the dimension of the conductor tuning rod increases for a given cylindrical conductor cavity system, we developed a cavity system with a large dimensional tuning rod in order to increase this. We, for the first time, employed not only a piezoelectric motor, but also gears to drive a large and accordingly heavy tuning rod, where such a combination to increase driving power can be adopted for extreme environments as is the case for axion dark matter experiments: cryogenic, high-magnetic-field, and high vacuum. Thanks to such higher power derived from the piezoelectric motor and gear combination, we realized a wideband tunable cavity whose frequency range is about 42\% of the central resonant frequency of the cavity, without sacrificing the experimental sensitivity too much.