3-d reconfiguration of electromagnetic field in multiwave cerenkov generator

Summary form only given. To date, the record power in X-band and millimeter-wave band is realized relativistic multiwave devices. The best result (15 GW in X-band) was obtained in the multiwave Cerenkov generator (MWCG). Design features of MWCG are the following: a) 3-D oversized electrodynamics system: b) the generation frequency is determined by the interaction between electron beam and electromagnetic field at the frequency close to the cutoff of periodical system; c) focusing static magnetic field plays important role in the interaction process. The possibility to use PIC-codes for analysis of multiwave devices has appeared just recently. In this paper the results of computer simulations of two-section MWCG are presented. Parameters of electron beam and electrodynamics system correspond to the experimental device. Spatial distribution of the RF field in the MWCG was tracked from generation start up to the maximum of beam current. The influence of the operating mode in the first section on the evolution of radiation spectrum was studied. Operating mode depends on the reflection of electromagnetic wave from the cathode. It was showed that two modes can be realized mainly. Each of them has specific spatial distribution of electromagnetic field. In the first mode, the stationary radiation lasts for 50-60 ns. It's frequency is about 11-12 GHz. After this time mode hopping takes place. In the second mode, the spectrum of radiation and power remain constant during 100 ns.