Investigation of damage traces on the SWS of the RBWO with a low guiding magnetic field

Physics of Plasmas, Volume 28, Issue 5, May 2021. For the high power microwave (HPM) generator, damage on an RF structure surface is harmful for a long time operation. In this paper, we investigate damage traces on slow-wave structure (SWS) of the relativistic backward-wave oscillator (RBWO) with a low guiding magnetic field. By theoretical and experimental analysis, we find that damage traces on SWS surface are mainly caused by the bombardment of beam electrons pulled back. Moreover, it is suggested that damage traces are not caused by RF breakdown, the bombardment of secondary electrons, and the bombardment of particles from collector plasma. Importantly, to decrease damages and prolong the working life of the RBWO with a low guiding magnetic field, the electric field which pulls electrons to the RF structure surface (saying Ez and −Er) should be decreased by special design for the RF structure, such as blending and parameters adjustment. Those results may offer benefit guides for study of the RBWO with a low guiding magnetic field.