Recent Activity and Results on Gyro-TWT at the IAP

An overview of recent researches at the Institute of Applied Physics (IAP) involving the broadband gyrotron-traveling-wave tubes will be presented. A cascade of two helically corrugated waveguide (HCW) gyro-TWTs is under development, one of which possesses high gain whereas the second tube with about 20 dB gain is designed to produce 200–400 kW pulsed power in W-band. A high-gain tube has been “hot” tested in pulsed and CW modes. An appropriate cusp electron gun and an input/output microwave system for the high-power tube have been designed. Periodical sequences of short high-peak-power microwave pulses with wide spectrum were generated in HCW gyro-TWT experiments on K-band CW tube with high external reflections and Ka-band pulse tube with a cyclotron saturable absorber in the feedback loop. A recently proposed gyro-TWT using a quasi-optical zigzag-like transmission line enabling amplification within more than octave frequency band (with adjusting the B-field) will also be discussed.