Full 3-D Simulation and Optimization of Gigawatt Class C-Band 20% Efficient Coaxial Vircator

An investigation of several configurations of a gigawatt class coaxial triode vircator is presented. To maximize averaged power output efficiency, several device dimensions are optimized. Simulations of the source were carried out using a full 3-D simulation code called improved concurrent electromagnetic particle in cell (ICEPIC). The optimization method used was a gradient-free method called asynchronous parallel pattern search. The optimization was run until convergence; until efficiency would no longer increase. The converged optimization resulted in a device that has 2.08 GW of output power with a steady-state efficiency of 20%. The device's output power is almost pure in the TM01 mode. The operating frequency is approximately 4.43 GHz, a frequency band previously unexplored for gigawatt class vircators. Additionally presented is a configuration designed to mitigate explosive emission on undesirable surfaces along the cathode. The configuration successfully keeps nonemission surface E-fields below 300 kV/cm. It maintains multigigawatt output power at 1.86 GW and has an operating frequency of 4.43 GHz.