Calculating of Coupling Factor of Microwave Electron Gun

To design the coupler of a designing microwave electron gun, we use “energy method” proposed by Derun Li, et al. The intrinsic Q of the electron gun cavity is very high: about 20000. The method is to calculate the intrinsic and external Q values of a cavity coupled to a waveguide, using MAFIA code in time domain. The comparisons between simulation and experimental results are given for a set of different coupling lengths. The result shows that “energy method” works efficiently for high Q cavities.