Investigation of the power balance in advanced divertor configurations on MAST-U.

This project is concerned with fusion energy research, which has the potential to produce energy from limitless supplies of fuel on the Earth. The UK is a world leader in the development of fusion, and it is a growing part of the government's current industrial strategy. Fusion will be a major source of electricity well into the future, and has the potential to achieve this without any high-level radioactive waste, or carbon dioxide emissions.

The most well-developed approach to fusion is the "tokamak", a ring doughnut shaped chamber in which hot plasma fuel is confined. The temperatures required for fusion to occur are in excess of 100 million degrees Celsius, providing a significant challenge to handle the heat flux at the boundary of a reactor. The power and particles exhausted from a tokamak are directed into the divertor and onto the plates, which are designed to handle the significant power loads ejected from the plasma. These could be up to 1 GW per square metre in next step devices at times; even higher in a fusion power plant. Control of this is therefore crucial to the successful operation of a power plant, as these loads are intolerable, and will lead to material failures.

One means of controlling the power load to the target is through the use of advanced divertor geometries, such as X-divertor and Snowflake, and importantly Super-X, which aim to both spread the power over a larger geometric area, and also allow a greater amount of the power to be radiated. The Super-X does this to a greater extent than the others, and the facility used for these experiments (MAST-Upgrade, a £55M upgrade, funded by EPSRC) will be the first
experimental facility in the world capable of testing the Super-X divertor.

A key question to be addressed by this project is whether past studies of sources and sinks of power (known as power balance) properly accounted for all effects. This project will allow for details which have been overlooked in the past, to ensure that there is a robust method of doing power balance going forward to MAST-Upgrade. This method will then be used to determine whether the MAST-Upgrade has different power balance to MAST, even when conventional divertors are used. The primary aim of this project is to determine quantitatively and experimentally the effectiveness of the Super-X divertor concept in reducing the heat and particle loads to tokamak divertors. The work of this project will also inform studies on other European facilities, funded by EUROfusion. Finally, this project will contribute more generally to the development of compact fusion power plants, a key part of UKAEA research strategy.