STUDY OF A PLASMA-FILLED X-BAND BACKWARD-WAVE OSCILLATOR

We present experimental studies of a plasma-filled X-band backward wave oscillator (BWO). Depending on the background gas pressure, microwave frequency upshifts of up to 1 GHz appeared along with an enhancement of a factor of 7 in the total microwave power emission. The bandwidth of the microwave emission increased from less-than-or-equal-to 0.5 to 2 GHz when the BWO was working at the rf power enhancement pressure region. The rf power enhancement appeared over a much wider pressure range in a high beam current case (10-100 mT for 3 kA) as compared to a lower beam case (80-115 mT for 1.6 kA). The plasma-filled BWO has higher power output compared to the vacuum BWO over a broader region of magnetic guide field strength.