Design of broadband kilo-watt class W-band serpentine TWTs

Summary form only given. The design of a traveling-wave tube (TWT) amplifier chain capable of 2.5kW of peak RF output power and > 1.5 kW of power over the frequency band of 92 - 100 GHz will be presented. This amplifier configuration is comprised of a driver TWT and two serpentine TWT power boosters, which are cascaded in series. The driver TWT is driven by a 122 mA, 20 kV electron beam and is expected to yield an RF peak power of 245 W with >100 W of power over a 7 GHz band-width [1]. This driver tube is currently under development [2]. The booster amplifiers are driven by much more intense 533 mA, 20 kV electron beams formed via a novel beam forming approach. The beam is focused by a solenoidal magnetic field of 6 kG in a 420-μm diameter beam tunnel. The higher beam perveance of booster TWTs in this cascaded configuration [3] permits a much higher RF power-bandwidth product out of the first and second booster stages than presently feasible with conventional approaches. Shown in the plot below are the predicted frequency responses of the first and second booster stages with an assumed constant 100 W drive power into the first booster stage. These results are obtained with simulations using the 3D particle-in-cell code Neptune with beam phase space information imported from 3D Gun/Collector code MICHELLE. The booster circuits are very compact with circuit lengths of approximately 2 and 1.4 cm for the first and second booster stages, respectively. Gun and booster designs will be presented and discussed.