PI Loop Resonance Control for Dark Photon Experiment at 2 K Using a 2.6 GHz SRF Cavity

TL;DR

This paper presents a PI loop control method using piezo actuators to stabilize and match the frequency of two 2.6 GHz SRF cavities at 2 K for dark photon experiments, addressing microphonics and drift issues.

Contribution

It introduces a PI loop control system with three piezo actuators for frequency stabilization and matching in SRF cavities used in dark photon searches.

Findings

Successful frequency stabilization using the PI loop.

Effective matching of cavity frequencies within bandwidth.

Simulation of integration time for control system.

Abstract

Two 2.6 GHz SRF cavities are being used for a dark photon search at the vertical test stand (VTS) in FNAL, for the second phase of the Dark SRF experiment. During testing at 2 K the cavities experience frequency detuning caused by microphonics and slow frequency drifts. The experiment requires that the two cavities have the same frequency within the cavity's bandwidth. These two cavities are equipped with frequency tuners consisting of three piezo actuators. The piezo actuators are used for fine-fast frequency tuning. A proportional-integral (PI) loop utilizing the three piezos on the emitter was used to stabilize the cavity frequency and match the receiver cavity frequency. The results from this implementation will be discussed. The integration time was also calculated via simulation.