Design and Simulation of a $Q$ -Band Gyrotron Backward-Wave Oscillator With Distributed Loss

This paper presents the design and simulation of a Q-band gyrotron backward-wave oscillator that is operated at fundamental TE01 mode. A tapered interaction circuit with distributed loss is employed to suppress both the transverse and axial mode competitions. A nonlinear code is used to study the start-oscillation current and interaction behavior. A Computer Simulation Technology (Particle In Cell) (CST-PIC) method is employed to verify the numerical calculation. A simulation result of 127-kW output power and 22.7% efficiency with a 3-dB bandwidth of 1.3 GHz driven by a beam of 70-kV voltage and 8-A current is predicted. The results of nonlinear code and CST-PIC calculations show good agreement.