Second-harmonic fundamental-mode slotted peniotron

Summary form only given. The harmonic peniotron has been demonstrated to be a highly efficient generator of millimeter-wave power (Ishihara et al., 1999). Since a practical peniotron design must provide immunity to mode competition from gyrotron interactions as well as high device efficiency, the UC Davis peniotron design (McDermott et al., 2000) employs an overcoupled interaction cavity for a predicted device efficiency of 47% at 34 GHz. Stability will be ensured by operation in the lowest order mode of a slotted four-vane (magnetron type) circuit, the pi/2 mode. The TE11-like pi/2 mode couples well to the TE11 mode of the circular output waveguide through the 2.5 mm radius iris at the end of the cavity. The output diffraction coupling configuration results in heavy loading of higher order axial modes and avoids mode conversion in the output waveguide. For diagnostic purposes, the experimental device will also incorporate side-wall coupling to the cavity. The peniotron will operate with a 70 kV, 3.5 A, vt/vz=1.5, axis-encircling electron beam generated by a recently developed Northrop Grumman Cusp gun (Gallagher et al., 2000). Large-signal simulation of the interaction predicts an electronic efficiency of 58% and an extracted power output of 120 kW (47% device efficiency). The overall efficiency can be raised to 57% by use of a depressed collector.