Speaker
Description
The ORGAN experiment seeks to detect axion dark matter through its resonant conversion to microwave photons inside a strong magnetic field. With the ORGAN 1b run complete, attention turns to ORGAN 2a, which will probe the previously unexplored 15.96–16.15 GHz band, corresponding to axion masses of 66.0–66.8 μeV. Here we describe the design, optimisation, and performance of the rectangular resonant cavity developed for this search.
We adopt a DC tuning mechanism in which piezoelectric actuators translate one cavity wall, shifting the resonant frequency without additional structures inside the cavity. Operating the piezoelectric actuators under a static DC voltage, rather than as stick-slip positioners, avoids the heat dissipation and mechanical vibration associated with slip events, both significant concerns at cryogenic temperatures. Unlike conventional approaches based on rotating rods or movable dielectrics, mechanical complexity is avoided and the interior remains unobstructed, maintaining a form factor of approximately 0.657 for a non-tilted wall.
The cavity dimensions were optimised analytically to maximise both geometry factor and volume, and hence the scan rate, under the requirement that mode crossings lie outside the target frequency band, preserving mode purity across the full tuning range. Positioning the wall with a single actuator inevitably introduces tilt, owing to assembly tolerances and alignment; we characterise this via the resulting mode separation and correct it with a dual-actuator configuration under PID feedback that restores the wall to its zero-tilt position.
Finally, we report the mechanical and cryogenic performance of the piezoelectric tuning system, along with pre-search measurements that demonstrate the viability of this approach for the ORGAN 2a campaign.
| Primary Abstract Topic | Experiment: Axions and Wave-Like-DM |
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