A multistage depressed collector with azimuthal magnetic field for gyrotrons

Multistage depressed collectors can open up new possibilities for enhancement of the overall efficiency of gyrotrons. A new method of spatial separation of electrons in the collector region is based on application of azimuthal magnetic field in combination with axial electric field. In this paper, we describe main features of this method and present a design of the 4-stage depressed collector system for the SPbPU's experimental 74.2 GHz, 100 kW gyrotron.