Compact Electron Beam Focusing System for Millimeter Wave Sources

We are pleased to report we are able to meet all of the performance metrics described in Navy SBIR 22.1 – Topic N221-037, Compact Electron Beam Focusing System for Millimeter Wave Sources, with the use of a mod-anode pulsed electron gun combined with a novel periodic permanent magnet (PPM) focusing. The electron gun Mod-Anode pulsing design is sufficient to permit a high pulse repetition frequency without the complexity of gridded cathode. In addition, the scope of our study encompasses the whole amplifier even though the topic focus is primarily on the compact beam generation and transport system. This is because the electron beam parameters and the focusing limit of the magnet are always dictated by the need of the beam-wave interaction circuit for efficient broadband high-power RF generation for use in the ultimate applications. The preliminary RF circuit design indicates that more than a factor of two enhancement in power-bandwidth product relative to current state-of-art amplifiers can be achieved with the proposed beam focusing approach. Based on these encouraging results, we propose the development of an integrated PPM-focused beamstick (gun, magnet, and collector) to fully demonstrate the electron gun and beam focusing approach during the Phase-II program. A full amplifier design will also be done as part of the Phase-II. However, the RF circuit development is not part of the proposed Phase-II due to limited resources. It is highly recommended that the RF circuit development be pursued under a parallel path, which if successful can be integrated into the beamstick at the end of Phase-II program once the beamstick has been fully qualified via testing.