W-band helical-waveguide gyro-TWTs yielding high gain and high output power: Design and simulations

A cascade of two gyrotron travelling-wave tubes (gyro-TWTs), one of those possesses a relatively high gain (46 dB) while the other provides high output power (350 kW) at the moderate (22 dB) gain, is under design and modeling. Both gyro-TWTs use helically corrugated waveguides and operate at the second cyclotron harmonic. A principal scheme of such an amplifier chain is discussed including issues of microwave input, output and transmission between the tubes. Computer modeling of the beam-wave interaction using CST Particle Studio PIC Solver shows feasibility of achieving of 350 kW pulse output power with 6-8 GHz bandwidth when driving by a 50-mW input source at W-band.