Recent test results on a 95 GHz, multi-megawatt gyrotron

Summary form only given: A 95 GHz, multi-megawatt continuous-wave (CW) gyrotron oscillator is currently under development at CPI. The initial experimental campaign demonstrated peak output power levels up to 1 MW at 40 A beam current for pulse lengths up to 5 ms, and output power of 630 kW at 25 A beam current for pulse lengths up to 15 s. Modifications to the CPI test stand were then implemented to allow for short-pulse operation with beam currents up to 75 A. In the second experimental campaign, power levels up to 1.45 MW were obtained, but efficiency at high beam current was limited, apparently due to oscillations in the gyrotron beam tunnel. The gyrotron is currently (as of January, 2009) being rebuilt to address beam tunnel oscillations and to thereby improve beam quality in the interaction cavity. A third experimental campaign to test the rebuilt gyrotron is scheduled to occur within the next few months. Results of these tests will be presented.