Compact, multi-kW sheet beam oscillator at 94 GHz

Summary form only given. An extended-interaction oscillator (EIO), driven by a 20-kV, 4-A sheet electron beam having a cross section of 0.3 × 4 mm, is described. This new EIO is an outgrowth of our recently demonstrated sheet-beam-driven, 94-GHz extended interaction klystron (EIK) amplifier, which has produced a peak power of over 7.5 kW.^{1, 2} The size and weight of these devices are dictated by the permanent magnet solenoid used to focus the electron beam through the circuit, and they scale approximately as L²B, where L and B are the length a magnitude of the uniform field region. The oscillator configuration consists of a single 11-gap cavity that is 0.9 cm long, so the full circuit is about half the length of the amplifier. Consequently, the oscillator is both much simpler (no input coupler and driver required) and about 25% the size and weight of the amplifier. Overall dimensions are 18 × 22 × 8 cm, with a weight of less than 16 kg. Neptune³ particle-in-cell simulations predict a peak output power of 9.5 kW from the oscillator. The power is maximized by varying the number of gaps in the cavity, by tapering the gap spacing within the cavity, and by adjusting the size and positioning of the coupling iris. Oscillator design considerations for peak and average power and comparisons with the amplifier will be discussed.