Assessment of flake graphite cathode performance with dissimilar surfaces in relativistic magnetrons

Abstract In order to achieve high performance relativistic magnetrons, cathode material technology has been significantly developed. However, for some commonly used materials, such as graphite, the performance level and improvement room of its performance in RM operation are still unclear. Therefore, in this paper, the smooth flake graphite cathode and the varying degrees of roughened one are tested in permanent magnet packaging rising-sun relativistic magnetron. Then, particle in cell simulations were performed to evaluate the results of the experiments. The experiment results show that, under a peak voltage of ∼400 kV, the peak microwave power of relativistic magnetron with smooth surface is 156 WM, while that of graphite with completely roughened surface is 335 MW. When the roughened area is greater than 225°, the difference in peak power of the microwaves is less than 13%. With the same voltage waveform, the simulation results show that the peak output power of this relativistic magnetron should be 538 MW. The simulation results indicate that even for completely coarsened graphite, the surface emission defect area may still exceed 13%, while the surface emission defect area of smooth graphite exceeds 30%. The results of this paper are intended as a potential contribution to relativistic magnetron cathode design and experimental analysis.