Development and test of a 500-kW, 8-GHz gyrotron

An 8-GHz gyrotron that generates 500 kW and is capable of depressed collector operation is discussed. The output is extracted transversely from the circuit goes into two WR 137 rectangular waveguides through modified pillbox windows. The device will be used for lower hybrid heating of the FTU tokamak in Frascati, Italy, and has consequently been designed to produce over 400 kW when operated at a 4:1 VSWR. The current tube produces 1-s pulses every 10 min with the output power adjustable from approximately 150 to over 500 kW by changing only beam and mod anode voltage. The sensitivity to operating parameters is extremely low, making the tube easy to operate and unusually tolerant of variations in voltages and currents. >