NEW RESULTS AND APPLICATIONS FOR THE QUASI-OPTICAL GYROTRON

The quasioptical gyrotron (QOG), which features an open resonator formed by a pair of spherical mirrors instead of the conventional gyrotron waveguide cavity, has been under development at the U. S. Naval Research Laboratory as a tunable high power millimeter-wave source for tokamak plasma heating, advanced radars, and power beaming. Results have recently been obtained for a quasioptical gyroklystron (QOGK) realized by the addition of an open-mirror prebunching resonator driven by an 85 GHz, 1.5 kW extended interaction oscillator. Efficiency enhancement by mode priming has been investigated, and efficiencies up to 19% have been obtained by increasing the frequency detuning of the operating mode. An overall efficiency of 30% was obtained by the addition of a simple depressed collector. Phase-locked operation was demonstrated at a power of 57 kW and efficiency of 16%. The high circulating power in the QOG resonator is currently being considered for use as an electromagnetic wiggler for compact infrared free-electron lasers. The QOG is also promising as a source for an active sensor of upper atmosphere trace impurities.