Design and Experiment of an \textit -Band High-Efficiency Gyro-TWT Demonstrating 100-kW 1-Second Long-Pulse Radiations

In this article, the design and test results of an \textit{X} -band high-efficiency long-pulse gyrotron traveling wave tube (gyro-TWT) based on a lossy ceramic-loaded high-frequency (HF) circuit with an operation mode of TE _{\text{11}} are presented. In the design, a pill-box input window, a magnetron injection gun (MIG), a room-temperature coil magnet, and a double-disk output window are adopted. A single-stage depressed collector (SSDC) is applied to enhance the efficiency of this amplifier and to reduce the dissipated beam power. In the hot test, with the beam parameter of 70 kV and 5 A, and the depressed voltage of 20 kV, this \textit{X} -band gyro-TWT produces 104 kW, 1-s long-pulse radiations at 7.8 GHz, corresponding to a saturation gain of 32.2 dB and a maximum overall efficiency of 41.6%, the measured - 3-dB power bandwidth exceeds 0.4 GHz.