MAST Upgrade microwave heating and current drive system – engineering design overview

MAST-Upgrade (MAST-U) is undergoing several enhancements to deliver increased performance and functionality. One such enhancement is the design, development, and implementation of an Electron Bernstein Wave (EBW) Heating and Current Drive (HCD) System. The MAST-U EBW System aims to provide experimental data for model validation, and to provide a greater understanding of EBW physics and its capabilities. The MAST-U EBW System provides up to 1.8 MW of microwave power into the plasma, through a system comprising: high voltage power supplies; two gyrotrons; evacuated transmission lines; a steerable in-vessel launching system; and associated control and ancillary systems. The gyrotrons from Kyoto Fusioneering have a 0.9 MW output power capability at the dual frequencies of 28GHz and 34.8GHz, allowing start-up and current drive studies to be carried out at their respective optimum frequencies. Additional diagnostics, termed interceptor plates, are proposed to sit in the path of the first reflection. These will measure the reflected power from the plasma, to both act as an interlock if the reflected power is too high, and provide key information on the coupling efficiency.