Effect of Cathode Surface Roughness on Quality of Electron Beam in a Gyrotron Electron Optical System

An approach to simulate electron trajectories in gyrotron electron optical systems taking into account cathode surface roughness is proposed. It is based on the use of standard parameters of the thermionic emission model, which is available in the three-dimensional simulation software, for consideration of the micron-size non-uniformities of the cathode surface. Based on this approach, the influence of cathode surface roughness on electron beam quality in the 74.2 GHz, 100 kW gyrotron is studied. A comparison between the simulated data and the data obtained earlier in the experiments on velocity spread allows to estimate an averaged size of microstructures on the surface of a lanthanum hexaboride cathode used in this gyrotron.