Coaxial all cavity extraction in the Recirculating Planar Magnetron

Recent experiments on the first Recirculating Planar Magnetron (RPM) prototype, the L-band RPM-12a, have demonstrated successful generation of microwave power in the vicinity of pi-mode at 1 GHz using a -300 kV pulsed voltage and 0.2 T axial magnetic field. However, these initial experiments were designed primarily to demonstrate feasibility and validate the RF dispersion relationship. This prototype has not demonstrated the efficient extraction of microwave power into waveguides. A novel approach to power extraction using a coaxial adaptation of the “all cavity extractor” is currently under development at the University of Michigan. The Coaxial All Cavity Extractor (CACE) is a highly compact axial extraction technique that is specifically designed to accommodate the planar slow wave structures of the RPM. Concepts and design of the extractor are presented as well as a new experimental prototype RPM-CACE, a 12-cavity device simulated to yield 450 MW with 60% efficiency at 1.9 GHz.