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 will inject up to 1.8 MW of microwave power into the plasma, via two microwave beams, at the dual frequencies of 28 GHz and 34.8 GHz.

The beams are launched into the plasma via an in-vessel launching system, which is designed to provide maximum experimental flexibility. An ex-vessel switching arrangement allows the selection of on- or off-axis injection into the plasma via either the mid-plane or upper launcher. Each launch path has multiple mirrors, with the final mirror in each path being a flat, steerable mirror to vary the injection angle, with a high positional accuracy and precision. Additionally, the on-axis launcher has large angular steering ranges to allow for both co- and counter-plasma current injection. Furthermore, one on-axis launcher path can be redirected for microwave-assisted start-up experiments.

Several graphite plates, termed interceptor plates, are proposed to sit in the paths of first reflection from the plasma. These will measure the reflected power from the plasma to act as an interlock if the reflected power is too high, provide key information on the coupling efficiency and protect the vacuum vessel by dispersing incident power. Other diagnostics will measure stray radiation inside the tokamak and emission produced by Parametric Decay Instabilities (PDI).

This presentation outlines the key objectives of the system, the preliminary system design, and the current status, with particular focus on the in-vessel design and challenges associated with the chosen frequencies and spatial integration constraints.