Damping of vibrations in superconducting quarter wave resonators

Ambient mechanical vibrations could cause significant detuning in superconducting accelerating cavities, disturbing the acceleration regime. The mechanical damper, first developed at Laboratori Nazionali di Legnaro, Istituto Nazionale di Fisica Nucleare by A. Facco [Mechanical mode damping in superconducting low β resonators, in Proceedings of the Eighth Workshop on RF Superconductivity, SRF’97, Abano Terme (Padova), Italy, 1997 (JACoW, Geneva, 1997)], dissipates the kinetic energy of vibrations due to friction. The study of damping efficiency, corresponding to the maximum cavity detuning, is addressed in this paper. The mechanism of the damper parameters impacting on the maximum cavity detuning at a given excitation is investigated. An analytical model of the damper has been derived to predict the nonlinear response. Numerical results from simulations in ANSYS confirmed the model over a wide range of excitation. An experimental demonstration has been conducted successfully on a test bench. Online measurements taken on the ISAC-II superconducting linac at TRIUMF further verify the analytical model