Particle-in-Cell simulation of gyro-TWT using a metal PBG circuit

The Particle-in-Cell (PIC) simulation of a Ka-band Gyrotron Traveling Wave Tube (gyro-TWT) amplifier using a Metal Photonic Band Gap (MPBG) waveguide as its RF interaction circuit is presented to study the electron beam-RF wave interaction behavior. The MPBG guide is chosen as an RF interaction circuit to accomplish the single mode operation in the amplifier by its mode selective property at short wavelengths. The technique for generating hollow annular gyrating electron beam is demonstrated using “CST particle studio” code. The energy transfer phenomenon from the gyrating hot electron beam to the propagating electromagnetic (EM) wave has been studied. The PIC code predicts that the peak output power in the MPBG loaded gyro-TWT as ~ 90 kW at 35 GHz with an electronic efficiency of ~ 13 % for a velocity ratio of 1.05. The saturated gain has been calculated as ~ 40 dB and the 3 dB instantaneous bandwidth is obtained ~ 14%.