Design and Cold Test of a Mode-Suppression Circuit for the G-Band Gyro-TWT

In this paper, the design and measurement of a mode-suppression circuit used in the nonlinear interaction region for a G-band gyrotron travelling wave tube (gyro-TWT) are presented. By achieving sufficient coupling losses, this circuit can effectively suppress the parasitic oscillations without affecting the operating mode, thus improving the tube stability during high power operation. The measured results agree well with the simulated results, which can provide a loss of 5.6 dB/cm to suppress the backward-wave oscillation (BWO) of the TE21 mode. This proves that the circuit can be used as a new scheme for gyro- TWTs to achieve high stability and high power.