Simulation and Measurement of an Interaction Structure With Distributed Radiation Coupling Circuit for a High-Power Ku-Band Gyro-TWT

Design and measurement of a distributed radiation coupling (DRC) circuit for the Ku -band TE11-mode gyrotron traveling wave tube (gyro-TWT) amplifier are presented. Different from the dielectric-loaded (DL) waveguide, the proposed DRC circuit can suppress the parasitic modes by achieving sufficient radiation coupling losses. It has the merit of lowering the microwave power loss density, which can improve the tube stability and average power-handling capability. Based on this proposed DRC circuit, a Ku -band TE11-mode gyro-TWT was designed and the particle-in-cell (PIC) simulation shows it can obtain a saturated output power of over 150 kW from 15.3 to 17.2 GHz for an electron beam with a velocity spread of 4.35%. As a comparison, the maximum average microwave power loss density is only 20% of the DL circuit under the same operating parameters. For verification, a DRC circuit was manufactured and cold tested. The maximum deviation between the measured results and our analysis is within 10%.