Scaling of 85 GHz gyrotron to operate at 94 GHz

This paper describes how a 94 GHz, 70 kV gyrotron operating in the TE13 mode was designed and built. The novel feature of the design is that it was based to a large degree on a previously built gyrotron that operated at a lower frequency. The highest efficiency achieved was 32% at 4 A, which agrees well with theoretical predictions. However, the maximum theoretical efficiency is about 45% at 10 A, but measured efficiency at this value of current was less than 20%. The highest power measured was 135 kW at 12 A.