Robustness of the E×B MDC prototype design for gyrotrons

The Short-Pulse (SP) E × B Multistage Depressed Collector (MDC) prototype developed and built at Karlsruhe Institute of Technology (KIT) is theoretically investigated for its robustness to manufacturing tolerances and non-optimized gyrotron operating scenarios. The tolerance analysis is done based on a parametric definition of the collector electrodes for the optimized gyrotron operation with the KIT 2 MW 170 GHz coaxial-cavity gyrotron. The six most dominant geometrical parameters are considered. The prototype design is then adapted to 5 different gyrotron configurations and operation modes, which include the Wendelstein 7-X (W7-X) Upgrade SP gyrotron for 140 GHz and 105 GHz operation, as well as the coaxial-cavity gyrotron in multi-frequency operation at 136 GHz and 204 GHz (in addition to the nominal operation at 170 GHz) and operation at the second harmonic at 170 GHz. The necessary modifications to the mechanical adaption, the magnetic configuration and electrode potentials are highlighted for promising MDC operation in all cases. • Geometrical definition of the KIT multistage depressed collector prototype. • Investigation of geometrical tolerances with the E × B design. • Different gyrotrons operated with the same multistage depressed collector. • Guidelines for future experimental verification.