A novel method for Lorentz force detuning compensation in multi-cell superconducting RF cavity and its validation at room temperature

Abstract

A tuner is an important element of a superconducting radio frequency (SCRF) cavity, which is used to tune the cavity at resonance frequency. The measurement and control of the pulsed detuning phenomenon is very challenging and can be measured in the superconducting state of the cavity at a high voltage gradient. This paper describes an innovative method and unique approach for the measurement of dynamic changes in resonance frequency of the SCRF cavity even at room temperature. For this purpose, a 1.3 GHz nine-cell prototype dressed cavity with RRCAT’s designed X-link tuning device is used. A test setup for measurements of dynamic changes in resonance frequency of the RF cavity has been designed and developed. The cavity response for piezo-excitation at various pulse widths has been determined. In order to simulate the Lorentz force detuning (LFD) effect, the source frequency has been modulated similar to the superconducting scenario in the SCRF cavity. To compensate the simulated detuning, a fast tuner is operated with half sinusoidal pulses at various combinations of pulse width and time advance to find out an optimum waveform. This optimized waveform will be used with a fast tuning control system to control LFD under actual operation conditions of the SCRF cavity.