Multimode simulations of an 85 GHz quasioptical gyroklystron experiment

Summary form only given, as follows. The quasioptical gyrotron is under development at the Naval Research Laboratory as a high-power source of millimeter-wave radiation. A quasioptical gyroklystron experiment has recently been completed, where the electron beam is prebunched in an upstream resonator by an external 85-GHz drive source. Typical operating parameters are 70 kV beam voltage with a current of 6 A, resulting in /spl sim/100 kW output power at 20% efficiency. The output spectrum of the gyroklystron is single-moded even though the longitudinal mode density is high. A depressed collector is used to increase the overall efficiency of the gyroklystron to 30%, which is easily implemented in the quasioptical configuration. The experiment has demonstrated mode priming, phase locking, amplifier operation, and a new technique called alpha priming. Nonlinear, time dependent, multimode simulations of the gyroklystron experiment have been performed. The computational model includes the effect of the finite rise time of the voltage, the variation of /spl alpha/(=/spl upsisub /spl perpspl upsisub /spl par) with time. the experimental magnetic field profile, and the presence of electron beam prebunching.