Optimization of an x-band TWT a using MAGIC PIC-FDTD code

2D simulation model of helix TWT is developed by MAGIC Code. This model contains electron gun and helix Slow-Wave Structure (SWS). 3D magnetic simulation is done by means of CST EM Studio and the axial periodic magnetic field is imported into MAGIC 2D. Absorber coating profile is measured using reduced-height rectangular waveguide and subsequently bulk conductivity for each segment is calculated to develop accurate simulation model. Simulation results are found to be in good agreement with experiments. This model is used to optimize output power with minimum change in structure, while suppressing Backward Wave Oscillation (BWO). As increasing power may lead to exceed some thermal limitations, 3D MAGIC simulation is also performed to calculate power loss of each element. Total power loss, caused by surface current and particle impact energy, is calculated and compared with those obtained without optimization.