Effect of Ion Bombardment Induced Cathode Degradation on the Performance of a Gyrotron Electron Gun

In this paper, effect of ion bombardment induced cathode degradation on the performance of electron gun is studied by simulation, for a 28GHz gyrotron with hollow beam electron gun. Simulations show that some ions generated within the gyrotron will bombard back to the cathode surface which may leads to degradation of the cathode as well as the gyrotron electron gun. for that the electron beam will be more dispersed compared with the original state, with the velocity dispersion increased by about 36% in this simulation. Meanwhile, velocity ratio of the electron beam will increase with the current decrease.