Novel magnetron-injection gun forming ribbon helical electron beam for terahertz gyrotrons of megawatt power level

Design of the planar magnetron-injection gun (MIG) forming ribbon helical electron beam (HEB) suitable for use in new generation of powerful planar gyrotrons is developed. The presented approach is based on three-dimensional numerical simulation of electron-optic system with taking into account the real three-dimensional configuration of the electrodes, beam space charge forces and such specific for MIGs factors as roughness of the emission surface and thermal velocities of electrons. Special attention was paid to the effect of particles drift in crossed electric and magnetic fields. Recommendations to diminish the velocity spread in the regimes with high enough (more than 1.3-1.4) pitch-factor are given. An analyzer of ribbon HEBs based on the retarding electric field method is proposed and optimized. The results of theoretical studies are in good agreement with the experimental data obtained at the IAP RAS by the mentioned above analyzer.