Mode-primed operation of an 85 GHz quasioptical gyroklystron

The quasioptical gyrotron (QOG) is currently under development at the U.S. Naval Research Laboratory as a high power source of millimeter-wave radiation. A quasioptical gyroklystron configuration has recently been realized by the addition of an open-mirror prebunching resonator driven by an 85 GHz, 1.5 kW extended interaction oscillator (EIO). The experiment is designed to operate at a voltage of 70 kV and beam currents of 5-15 A. The experiment is currently in progress, and results are presented for EIO mode priming and depressed collector operation at powers up to 100 kW. A technique for increasing the efficiency by adjusting the electron beam parameters on the rise of the voltage pulse is also described.