Status of the 500 kW: 8GHz gyrotron oscillator development program

In the frame of a development program aiming towards an 8 GHz, 500 kW, CW or long pulse (∼10 s) gyrotron, we are testing a 200 kW prototype. Its principal characteristics are: cavity mode = TE01, quality factor = 400, single anode magnetron injection gun insulated in a SF6 high voltage tank, beam voltage = 80 kV, maximum beam current = 25A, ratio p/sub perpendicular//p/sub parallel/≅1.9. The computed electronic efficiency is around 50%. The prototype has been tested at low current (I≤5A) and in short pulse (5 ms). The power obtained with a beam current of 4.8 A was 200 kW, yielding an efficiency of 50%. Tests are under way to completely characterize the tube. The next prototype designed to achieve a higher output power (≥300 kW) and longer pulse is under construction