Simplified Methodology to Evaluate Effect of Backscattered Electrons in Gyrotrons with Depressed Collectors

In gyrotrons with depressed collectors, some backscattered electrons go towards the RF cavity. Those reaching the cavity reduce the interaction efficiency and add excess heating load in a sensitive area; others are reflected back due to mirror effect. Mitigating the effects of backscattered electrons is critical for high power gyrotrons such as are needed for fusion research. This study provides a simplified method for evaluating which backscattered rays will reach the RF cavity, thus enabling comparisons of design options. An adiabatic approximation is used in the high field region in the vicinity of the RF cavity