High- Q Microwave Dielectric Resonator for Axion Dark-Matter Haloscopes

Abstract

The frequency band 1--15 GHz provides exciting prospects for resonant axion haloscopes as indicated by cosmological and astrophysical arguments. Among the challenges currently addressed to reach the required sensitivity, the development of high-quality factor cavities that tolerate multitesla fields plays a central role. We report a three-dimensional resonator based on a right-circular copper cavity with hollow cylinders that confine higher-order modes around the cylinder axis. Its effective volume at 10.3 GHz is $3.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}$ l, and under an 8-T field we measure an internal quality factor of more than nine million. A fine-tuning system limited to approximately $1$-MHz range is tested, useful for understanding the conditions required to run a haloscope with a cavity exceeding the axion quality factor.The cavity parameters we report demonstrate the potential of this unique resonator to probe galactic dark-matter axion at scan rates exceeding 2 MHz/day when the cavity is readout by a quantum-limited receiver.