Capacitive Fundamental Power Coupler and Pickup for the 56 MHz SRF Cavity

摘要

The beam excited 56 MHz SRF cavity will have a power coupler for a fast frequency tuner. The calculation shows the coupling of the power coupler, {beta}{sub opt}, is around 50. Size and location of the power coupler are determined by measurements. Measurements are in good agreement with the simulation results. The axial location of the power coupler for the Nb cavity is limited by corrugations made on the cavity outer conductor for purpose of removing any multipacting. The preferred axial location is 14.5 cm away from the cavity gap start where a slow tuner plate will be. MWS simulations are done to determine the length of the power coupler inner conductor and pickup probe for the Nb cavity at the fixed axial location. Size and location of both the fundamental power coupler and the pickup probe can be decided from the simulation results.