Electrical and thermo-mechanical analysis of beam recovery system for megawatt power gyrotron

•Electrical design of single stage depressed collector for high power gyrotron tube.•Efficiency enhancement by collecting spent beam.•Optimization of geometry and magnetic field for optimized beam spread.•Optimization of cooling duct system for better thermal management.

The paper presents the electrical and thermo-mechanical design of single stage beam recovery system for 120 GHz, 1 MW gyrotron. The electrical study shows that the cylindrical shape single stage beam recovery system enhances the efficiency by 66.26%. The maximum power deposited to collector in depressed collector operation is 0.48 MW for electronic efficiency, 30% and 1.44 MW for DC electron beam. The thermo-mechanical analysis has been performed to evaluate the water cooling system. The cooling system has capability of accommodating a peak wall loading, 0.9 kW/cm2 at flow rate of 1500 l/min for safe operating time, 60 ms. Further, a high voltage analysis is also carried out to appraise the electric field distribution in the collector.