Recent Advances in Relativistic MDOs

The relativistic magnetron is the most compact and efficient high-power microwave (HPM) source. It has been researched since Bekefi's pioneering work in 1975 at MIT. The performance of the relativistic magnetron did not dramatically improve until the \pmb2000s when new cathode concepts were introduced independently by researchers at the University of Michigan and at the University of New Mexico. These advances demonstrably decreased the time for onset of oscillations and increased the efficiency. All of these earlier works involved relativistic magnetrons with radial extraction. Researchers at the University of New Mexico then revisited the magnetron with diffraction output and most recently have shown in particle-in-cell simulations that its efficiency can exceed 90% when powered by a virtual cathode and leakage current is suppressed using a magnetic mirror. This paper summarizes our most recent advances.