Development and demonstration of a multi-megawatt 95 GHz gyrotron oscillator

A 95 GHz, multi-megawatt continuous-wave (CW) gyrotron oscillator is currently under development at CPI. The gyrotron consists of a single-anode magnetron injection gun designed to operate at 75 A and 90 kV, a TE_22,6 mode cylindrical interaction cavity, an internal mode converter to transform the TE_22,6 mode to a Gausssian beam, an edge-cooled CVD diamond output window, and a single-stage depressed collector fabricated from a strengthened copper alloy. During the initial experimental campaign, carried out in the Summer of 2007, peak output power levels up to 1 MW at 40A beam current were demonstrated at pulse lengths up to 5 ms. In addition, pulses up to 15 s in duration at 25 A beam current, the long-pulse limit of the CPI test stand, and 630 kW peak output power were achieved. In the Fall of 2007, modifications to the CPI test stand were made to allow for short-pulse operation up to 75 A. A second test campaign, aimed at demonstrating peak output power in excess of 1 MW, is planned for early in 2008.