PLASMA-FILLED GYRO-BWO

Recent theoretical studies have shown that the presence of plasma in t he high-power microwave (HPM) sources, when properly introduced, may e nhance the efficiency of the source. These findings have been confirme d by numerical simulations for some HPM sources. The enhancement has b een partly attributed to the neutralizing effect of the positively cha rged plasma on lowering the disruptive space charge effects of the ele ctron beam used to generate the radio frequency (RF), and partly attri buted to a modification of the dispersion relation leading to higher g roup velocities for the traveling RF waves. Mode selection may also be favorably affected by the presence of plasma in the source. Here we p resent the results of numerical simulations carried out to study the e ffect of plasma on a gyrotron device. Both neutral as well as positive ly charged plasmas have been explored. The gyrotron device is run in T E01 mode and generates a 12.75-GHz steady oscillation without any comp eting modes. The effect of the plasma at several different densities h as been explored. The presence of plasma at the densities explored do not show any significant enhancement of the gyrotron operation. Other plasma densities are being studied. The particle-in-cell (PIC) code us ed in simulations was the Mission Research Corporation (MRC) 2.5-dimen sional code MAGIC.