A 50 kW peak power, 4 kW average power, moderate confined flow, PPM focused, X-band TWT

Summary form only given, as follows. A 50-kW peak power, 4.0-kW average power periodic permanent magnet (PPM)-focused, X-band, coupled-cavity traveling-wave tube (TWT) has been developed. The tube exceeds this requirement by a considerable margin and has been tested to 10% duty to a minimum of 55 kW of peak power and 5.5 kW of average power across the operating band from 9.2 to 9.7 GHz. This performance represents the state-of-the-art in PPM-focused coupled-cavity TWTs. The tube achieves this performance by several innovations. It uses a novel confined flow-focusing scheme to minimize electron beam interception and also has improved cooling of the tube body. The RF circuit has separately cooled servers, a cooled output waveguide, and a cooled output window. At the output end, circuit pole pieces are laminated with copper and the gun and collector pole pieces have coolant manifolds brazed to them to provide axial cooling paths from the beam scraper and the refocusing section which follows the output window. The tube is focused with an array or thermocouples monitoring the temperature of the circuit. Temperature data indicate that the tube is not close to thermal runaway at 10% duty. Moderate confined flow focusing reduced RF defocusing to an acceptable level without substantially increasing the magnetic field from the value used for Brillouin focusing of the same beam. >