Long-pulse gyrotron-backward-wave oscillator experiments

Summary form only given, as follows. The Phillips Laboratory is investigating the physics of the gyrotron backward wave oscillator. Experiments are utilizing the RAMBO pulser, with electron beam parameters V/sub D/ = 400-800 kV; I/sub D/ = 1-50 kA; and pulse length = 1.3 /spl mu/s. The interaction cavity is designed to radiate in the frequency range of 4 - 5.5 GHz in a TE/sub 01/ mode. The interaction cavity has a radius of 4.37 cm and a length of 15 cm. A diode magnetic field is used for a field-immersed diode, and is tunable from 0 to 2 kG. The interaction region magnetic field is tunable from 3 to 7 kG. The diode and interaction magnetic fields are used together to provide a magnetic compression of the electron beam. C-band Vlasov antennas located at the diode end of the experiment are used to extract the backwave wave. Present experiments are concentrating on lengthening the current microwave output pulse length of 40-80 ns. Numerical simulations have been carried out with the 2 1/2-D PIC (particle-in-cell) code MAGIC.