Gyrotron Research at SPbPU: Diagnostics and Quality Improvement of Electron Beam

Methods of gyrotron electron beam diagnostics developed at St. Petersburg Polytechnic University are reviewed. Bremsstrahlung X-rays produced at the collector can be used for definition of electron energy distribution in the spent beam. This possibility has been tested at two megawatt-power-level gyrotrons at the Karlsruhe Institute of Technology. Analysis of propagation of gigahertz-frequency signals in a slow-wave structure coupled with the beam can be used for the determination of velocity characteristics upstream from the microwave cavity. Numerical simulations performed with CST Particle Studio confirmed that data on axial component of electron velocities can be derived from frequency dependences of the slow-wave gain. Control of electron beam quality via tuning of the electric and magnetic field distributions provides a promising instrument for gyrotron efficiency enhancement.