Microwave oscillation, mode control and extraction in the recirculating planar magnetron

Summary form only given. The recirculating planar magnetron (RPM) is a crossedfield device that combines the advantages of high-efficiency recirculating devices with those of planar devices: both large-area cathode (high current) and anode (improved thermal management). Preliminary experiments using the RPM-12a, the first L-band prototype, have successfully produced high power microwave pulses 50-300 ns in length at approximately 1 GHz . The device is driven using the Michigan Electron Long Beam Accelerator with Ceramic insulator (MELBA-C) which delivers a pulsed cathode bias of -300 kV for durations of 0.3-1.0 μs. The RPM is capable of generating 2-10 kA and is typically operated with an externally applied axial magnetic field between 0.18-0.2 T. Recent experimental work has focused on enhancing mode separation and cross-oscillator coupling using the mode control cathode (MCC). The MCC is a periodically slotted emission structure that provides RF feedback between oscillators and may be geometrically manipulated to improve mode separation independently from the anode structure. Future studies will continue to focus on phase locking using the MCC as well as a guided extraction mechanism for the planar slow wave structures. Power extraction is to be accomplished using on an adaptation of the “all cavity extractor” (Greenwood et al.) that uses a coaxial transmission line to axially extract RF power in the TEM mode. An experimental D-band RPM prototype using the coaxial all cavity extractor system is under design and construction; operation is anticipated for the summer of 2013.