Long-pulse operation of a MW-class pasotron

Summary form only given. It was demonstrated that a plasma-assisted, helix-based slow wave oscillator (pasotron) can operate coherently (1.2 GHz) at a megawatt power level, long pulse (about 0.6 msec), generating ~600 J of microwave energy per pulse without pulse shortening. This result was achieved in spite of significant drop in the power supply voltage, as well as nonconstant gas pressure in the tube during the pulse. Mode switching can occur if the power supply voltage drop is too large (~40%). The results obtained indicate that stable, single mode operation of the pasotron with output energy of one kJ per pulse and beyond can be realized