PIC Simulation Study of the Formation Mechanism of Periodic Virtual Cathodes in the Reltron

This paper presents the basic concept of the formation mechanism of virtual cathodes in the reltron oscillator. For this purpose, a typical experimental device is particle-in-cell (PIC) simulated to validate the simulation model using a commercial PIC code "CST Particle Studio." The formation of virtual cathodes and its repetition at the various positions inside the reltron structure during the RF build-up as well as stable microwave radiation from the device has been demonstrated using PIC simulation results. An interesting phenomenon of two stages of periodic formation of virtual cathodes in the reltron has been demonstrated. In the first stage, two virtual cathodes form simultaneously, one after the first grid and another after the third grid, while in the second stage, only one virtual cathode forms after the second grid. For sustained device oscillation, these two stages of the formation of virtual cathodes become a periodic process.