Increasing the diffraction losses in gyrotron beam tunnels for improved suppression of parasitic oscillations

High-power gyrotrons often suffer from parasitic oscillations in the compression region (beam tunnel) prior to the interaction cavity. A possible way to suppress the parasitic oscillations is to raise their starting currents by increasing the losses of the structure. In the present contribution we focus on the diffraction losses of the stacked copper-ceramic beam-tunnel geometry. Parametric simulations show that the diffraction losses can be significantly increased by optimizing the geometric characteristics of the structure.