Reflections in gyrotrons with radial output: Consequences for the ITER coaxial gyrotron

A theory describing the influence of reflections on operation of gyrotrons with radial output is presented. The theory is used for evaluating the effect of reflections on the operation of the $170 GHz$ ITER coaxial cavity gyrotron, which is under development in cooperation between EUROATOM Associations (CRPP Lausanne, FZK Karlsruhe, and HUT Helsinki) together with European tube industry (Thales Electron Devices, Velizy, France). It is shown that for optimally chosen external magnetic field value and electron beam radius, possible reflections do not change the final steady-state operation, which corresponds to generation of a $2.2 MW$ millimeter-wave power. The effect of deviation of the magnetic field and the beam radius from optimal values on the device operation is also studied.