Insights in the physics of the dynamic detuning in SRF cavities and its active compensation

Elliptical SRF cavities operated in pulsed mode experience dynamic Lorentz detuning because of the time varying radiation pressure. Due to the narrow electromagnetic bandwidth of these resonators, the induced detuning can severely affect their matching conditions to the RF feeding system. The active compensation scheme using piezoelectric tuners has proven to be a viable and attractive method to minimize the effects of the Lorentz detuning. To optimize this compensation, mechanical parameters are extracted for the action of the Lorentz forces and the piezoelectric tuner from both measurement and simulation. This process gives insights into the physics of the dynamic detuning, such as the nature of the coupling differences of both detuning sources, the possible settings for the measurement of the dynamic detuning with the methods to deduce mechanical parameters from them, and the origin of possible parasitic effects in the measurements. These issues are reported and discussed along with some ideas for the optimization of the detuning compensation.