Coupling parameter study of superconducting cavity coupler

A superconducting cavity coupler with coaxial symmetric structure is introduced. The coupling parameter of the coupler is analyzed by the SUPERFISH program. The curve of the coupler inner conductor position versus coupling parameter is obtained. The analyze result of coupling parameter is according with the experiment of a model cavity. As a result, the coupling parameter of CAEP superconducting photocathode injector experiment is given: coupling parameter is 1637, the position of coupler inner conductor is 15.45cm and the average accelerating field is 20MV/m.