Recent developments in millimeter wave gyro-TWT research at NTHU

The authors report experimental and theoretical studies of a severed Ka-band TE/sub 11/ mode gyrotron traveling wave amplifier (gyro-TWT) which achieved a linear gain of 40 dB, saturated gain of 35 dB, saturated power of 27 kW at 16% efficiency, and FWHM (full width at half maximum) bandwidth of 2.5 GHz centered at approximately 33.5 GHz. Comparison with the unsevered gyro-TWT experiments shows that the use of a sever reduces the TE/sub 21/ oscillation to a level that can be completely suppressed with less than 1 W of drive, while several hundred watts was required without the sever. Both linear and saturated gains are more than doubled because of the addition of the sever. Comparison with theoretical calculations gives reasonable agreement in linear gain and bandwidth, but the observed saturated power is approximately 35% lower than theoretical predictions.<>