Trajectory analysis in a collector with multistage energy recovery for a DEMO prototype gyrotron. Part III. Influence of the spent electron beam parameters

The influence of the spent electron beam parameters on the possibilities of multistage energy recovery in the prototype gyrotron developed for the DEMO project is determined. The characteristics of electrodes and magnetic coils in a collector with four-stage recovery were optimized considering the distributions of electrons' coordinates and velocities obtained as a result of calculating the electron-wave interaction in the cavity. In the trajectory analysis in the collector, a sectioned electron beam was used to suppress the negative influence of the bundles of a toroidal solenoid used to create an azimuthal magnetic field. The possibility of achieving the total efficiency of the gyrotron of approximately 78% was shown, which is close to the maximum total efficiency with ideal separation of electron fractions with different energies, with the current of electrons reflected from the collector not exceeding 1% of the total current of the electron beam. Keywords: Microwave electronics, gyrotron, electron beam, energy recovery.