Modelling and simulation of gyrotrons

Modelling and simulation of gyrotrons have two interconnected aspects, namely beam formation in the electron-optical system (EOS) and beam-field interaction in the resonant cavity. In this paper we address both problems and outline the physical models and numerical techniques implemented in our problem-oriented package of computer codes. In order to illustrate our approach we present some results of numerical experiments carried out at the FIR FU centre and directed towards analysis and optimization of the existing devices of the Gyrotron FU Series as well as applied to the development of simulation-based design (SBD) of a novel high harmonic gyrotron with the electron beam encircling the axis and a permanent magnet system.