High efficiency operation of a plasma-assisted slow-wave microwave oscillator at a MW power level

Summary form only given. Conventional microwave sources utilize strong axial magnetic fields to guide an electron beam through an interaction region. A plasma-assisted slow-wave microwave oscillator (Pasotron) can operate without external magnetic fields because the presence of ions neutralizes the beam space charge and allows for radial motion of electrons under the action of transverse fields of the wave. The inherent efficiency of conventional microwave sources based on interaction with the backward wave with a 1D electron flow is typically limited to 15-20%. The current thrust is to take advantage of the 2D electron motion in the Pasotron in order to demonstrate high efficiency operation at the megawatt power level. Indeed, an efficiency in excess of 40% was demonstrated experimentally at power level of 1 MW with the beam voltage of /spl sim/55 kV and currents in the range of 40-50 A. The biggest challenges associated with efficient, high power operation of the Pasotron are beam dynamics, power extraction and mode competition. Theoretical studies, PIC simulations and the experimental data all indicate that both steady state and transient beam-dynamics of the self-pinching beam in the Pasotron is well understood. Most recent theoretical and experimental activities will be reviewed, with an emphasis on stationary and non-stationary beam dynamics, beam wave interaction and efficient power extraction.