MAST Upgrade Divertor Facility: A Test Bed for Novel Divertor Solutions

Abstract

The challenge of integrated exhaust consistent with the other requirements in DEMO and power plant class tokamaks (ITER-like and alternative DEMOs, Fusion Nuclear Science Facility approaches) is well-known and the exhaust solution is likely to be fundamental to the design and operating scenarios chosen. Strategies have been proposed such as high main plasma radiation, but improved solutions are sought and will require revised research methodologies. While no facility can address all the challenges, the new MAST Upgrade tokamak enables exploration of a wide range of divertor plasma aspects in a single device and their relation with the core plasma (e.g., access to H-mode) and in particular the development of fundamental understanding and new ideas. It has a unique combination of closed divertor, capability of a wide range of configurations from conventional to long leg (including Super-X), and fully symmetric double null (plasma and divertor structures). To extrapolate to DEMO and power plant scale devices where full integrated tests in advance are not feasible yet different physics mechanisms may dominate, theory-based models are likely to be essential for confident performance prediction, optimization, and a “qualification” of the concept. Development and validation of such models is at the heart of the program around MAST Upgrade. Amongst the many areas to be explored, there will be a strong focus on the closely coupled topics of plasma detachment and cross-field transport mechanisms (e.g., plasma filaments), key ingredients of effective and reliable protection of the plasma-facing components at DEMO scale.