Development of an Electron-Optical System for a High-Current Relativistic W-Band Gyrotron

Based on numerical simulation, an analysis of the system for forming a helical electron beam for a high-current relativistic W-band gyrotron was carried out. In the system under consideration, a straightforward high-current beam with a current of 2 kA and an energy of particles of 500 keV is formed in a coaxial magnetically insulated diode with an explosive emission cathode, and then the primary pumping of transverse velocities in a non-uniform magnetic field of a short kicker coil occurs. Then, in the section of increasing magnetic field, the electron beam is compressed to the working radius and the transverse velocities of the particles increase to a state with a pitch-factor of ~1. To ensure the required shape of the guide magnetic field, the effect of screening the pulsed magnetic field by a conductive shell placed inside the solenoid is used. In contrast to an electron-optical system with a uniform guiding magnetic field, in a system with compression there is no partial interception of the electron beam by the wall of the transport channel, and such a system seems to be more resistant to parasitic self-excitation of the high-frequency field, which causes premodulation of the electron beam and prevents the effective operation of the device.