Numerical investigation of the influence of reflected collector electron current on gyrotron operation

In this work a technique for electron optics simulation of the electron beam in the overall gyrotron geometry is presented. The influence of the nominal RF fields in the cavity on the electron beam properties are also taken into account using the fixed profile approximation. Using the proposed approach, the study of phenomena which takes place all over the gyrotron is simplified. For demonstration of that possibility, the influence of the reflected electrons at the collector entrance on the gyrotron operation is investigated. The increase of the reflected electron current and the reduction of the generated RF power as functions of the depressed collector voltage are numerically estimated for the European 170 GHz, 1 MW gyrotron for ITER.
The deeper understanding of the influence of reflected electrons in gyrotrons with single stage depressed collector is crucial for the improvement of the overall gyrotron efficiency. In this workshop, the opportunity to exchange knowledge with other participants on that important topic for the gyrotron design and operation will be opened.