Numerical Study on Lorentz Force Detuning Compensation of βg = 0.9 650 MHz Elliptic Superconducting Radio Frequency Cavity

Radiation pressure acting on internal surfaces of the superconducting radio frequency (SRF) cavity in the pulse mode of operation generates periodic deformations of the cavity wall, which changes its resonance frequency. This shift in the resonance frequency, known as dynamic Lorentz force detuning (LFD), causes large reflections of input power from the cavity. The tolerance on detuning of SRF cavity, particularly in high-energy accelerators, is extremely limited due to its high quality factor. Therefore, compensation for dynamic LFD is imperative. In the literature, the implementation of compensating piezoforce pulse and its automation is formulated on the basis of experiments and control algorithms, such as proportional–integral feedback control, disturbance observer-based control, and active noise control. This article presents a compensating piezoforce pulse having a sinusoidal rise computed by gradient algorithm and an exponential decay optimized using a parametric study for limiting the dynamic LFD of
β_g
= 0.9 650 MHz elliptic SRF cavity. The applicability of the gradient algorithm has been demonstrated on a piezoelectric bimorph test structure by performing finite element analysis (FEA) and its experimental verification. Eventually, a compensating piezoforce pulse is applied to control the longitudinal vibration of the cavity for LFD compensation in coupled electromagnetic and structural FEA. The designed compensating piezoforce pulse demonstrates a significant reduction in dynamic LFD.