title: The external Q factor of a dual-feed coupling for superconducting radio frequency cavities: theoretical and experimental studies.
abstract: We propose a theoretical model based on network analysis to study the external quality factor (Q factor) of dual-feed coupling for superconducting radio-frequency (SRF) cavities. Specifically, we apply our model to the dual-feed 704 MHz half-cell SRF gun for Brookhaven National Laboratory's prototype Energy Recovery Linac (ERL). The calculations show that the external Q factor of this dual-feed system is adjustable from 10(4) to 10(9) provided that the adjustment range of a phase shifter covers 0°-360°. With a period of 360°, the external Q factor of the coupling system changes periodically with the phase difference between the two coupling arms. When the RF phase of both coupling arms is adjusted simultaneously in the same direction, the external Q factor of the system also changes periodically, but with a period of 180°.
authors.affiliation: Stony Brook University, Physics and Astronomy Department, Stony Brook, New York 11794, USA.
authors.forename: J
authors.initials: J
authors.lastname: Dai
authors.forename: S
authors.initials: S
authors.lastname: Belomestnykh
authors.forename: I
authors.initials: I
authors.lastname: Ben-Zvi
authors.forename: Wencan
authors.initials: W
authors.lastname: Xu