A design study of a magnetron injection gun for a gyrotron oscillator

A magnetron injection gun has been designed for an X-band gyrotron oscillator. The design is based on two-dimensional numerical analyses of the equi-potential surfaces and the electron trajectories. The gun can produce a helical beam of electrons with large perpendicular velocities to the magnetic field. The positional velocity spread of the emitting electrons remains within 12 percent just before injection into an open resonator. The variation of the velocities along the trajectory is studied and compared with that predicted by the adiabatic approximation. The approximation may yield an appreciable deviation due to the neglect of the inward drift of electrons. Typical parameters of the designed electron gun are presented.