Recent results from the University of Maryland overmoded BWO and MWCG program

Two classes of overmoded HPM devices are under experimental investigation by the University of Maryland : overmoded backward wave oscillators (BWOs) and multiwave Cerenkov generators (MWCGs), shown schematically in Figs. 1 and 2. Both structures use an overmoded, cylindrically symmetric, periodically corrugated slow wave structure (SWS), immersed in a strong axial magnetic field. In the case of the MWCG, two sections of corrugated waveguide are separated a smooth walled drift section which is not cutoff to the RF radiation. Our interest in the MWCG is the result of pioneering work done at the Institute of High Current Electronics in Tomsk, which produced a record 7.5 GW of microwave power in air at a wavelength of ∼ 3 cm.¹ The University of Maryland experiments operate at lower power and frequency, with the goal of improving our physical understanding of the overmoded BWO and MWCG.