Evidence of the 3π∕4 interaction mode in a compact magnetically insulated line oscillator process

Abstract

The electron beam generated in crossed-field devices such as the magnetron and the magnetically insulated line oscillator (MILO), which is closely related to the linear magnetron, interacts with a slow wave structure (SWS) in a configuration where the rf electromagnetic field is 180° out of phase from one cell to the next inside the periodic structure (the so-called π mode). We present here an analysis of a compact MILO device based on the U.S. Air Force geometry, where all dimensions are reduced by a factor of 2. By considering the geometrical parameters of the SWS, we establish precise criteria to maximize the microwave output power up to 3GW and to optimize the electronic efficiency up to 32%. To do so, the dispersion diagram is studied in such a way as to force the 3π∕4 mode in which the compact MILO oscillates. We report a discussion on the electromagnetic coupling in order to conclude on the output power stability of this interaction regime.