We present results from an experimental demonstration of a tunable thin-shell axion haloscope whose geometry decouples its overall volume from its resonant frequency, thereby evading the steep sensitivity degradation at high frequencies. An aluminum 2.6-l ($41{\lambda }^3$) prototype, which tunes from 7.1 to 8.0 GHz, was fabricated and characterized at room temperature. An axion-sensitive, straightforwardly tunable ${\mathrm{TM}}_{010}$ mode is clearly identified with a room-temperature quality factor, $Q$, of approximately $5000$. The on-resonance $E$-field distribution is mapped and found to agree with numerical calculations. Anticipating future cryogenic operation, we develop an alignment protocol relying only on rf measurements of the cavity, maintaining a form factor of 0.57 across the full tuning range. These measurements demonstrate the feasibility of cavity-based haloscopes with operating volume $V\gg {\lambda }^3$. We discuss plans for future development and the parameters required for a thin-shell haloscope exploring the postinflationary axion parameter space (approximately $4$ to $30$ GHz) at Dine-Fischler-Srednicki-Zhitnitsky sensitivity.

Close

PrevNext

View figure in article

• Optimization problems
• Optoelectronics
• Particle dark matter
• Axions
• Cavity resonators
• Microwave techniques
• Precision measurements
• Solid-state detectors