Realization of high efficiency in a plasma-assisted microwave source with two-dimensional electron motion

Summary form only given. A plasma-assisted slow wave oscillator (pasotron) may be operated without an external magnetic field allowing for radial motion of the electrons. This phenomenon has been exploited to achieve an increase in interaction efficiency from ∼20% to ∼50% by injecting electrons into the weak RF field region near the axis and having them bunch as they move axially and radially toward the surface of the slow wave circuit where RF fields are strong and efficient energy extraction occurs. Both in-situ diagnostics and analysis confirmed that the enhanced interaction efficiency is due to the fact that RF forces dominate the beam dynamics.