Recent Developments of the 2 MW Coaxial-Cavity Pre-Prototype Gyrotron Towards Multi-Frequency Operation

This paper gives a summary about recent activities at KIT regarding multi-frequency operation of the coaxial-cavity pre-prototype gyrotron. First, progress on gyrotron experiments above 200 GHz is discussed. Therefore, the existing 170 GHz design has been modified to achieve > 2 MW RF output power with an interaction efficiency > 35 % at 204 GHz operating in a new 10.5 T SC magnet. Second, research is ongoing to improve the cavity mode series for multi-frequency operation satisfying today's and future gyrotron requirements. Here, a new mode series is identified considering improved cavity cooling technology. This mode series shows only a small variation of the caustic radii and has electron beam parameters close to the existing mode series.