Design of double-anode magnetic injection with low velocity spread

A double-anode magnetic injection gun (MIG) was designed to satisfy demands of the 0.14 THz confocal gyro-travelling-wave tube (TWT). According to analytic trade-off equations, the initial parameters were determined first, then simulations and refinement were done with the PIC software. As a result, the horizontal-to-vertical velocity ratio of this MIG is 0.75, the axial velocity spread is 1.33%. The effect of some parameters, such as electrode shape, cathode magnetic field, mod-anode voltage and beam current on electron beam performance was discussed. The results indicate, all the parameters should be optimized sufficiently.