Flexible Grids for Complex Tokamak Topologies (Plasma Strand Project)

Supervisor: Peter Hill (University of York)

External Supervisor: Ben Dudson (LLNL)

The divertor of a tokamak is a critical power-handling component that must robustly handle extreme heat loads. Innovations and advances in physics understanding are needed to develop the advanced designs required for future fusion power plants. This project will develop numerical tools capable of modelling the complex processes and geometry needed to inform these designs.

The challenge that this project addresses is the complex magnetic geometry and topology of many advanced divertor designs. For example, snowflake divertors have multiple X-points, stagnation points in the poloidal magnetic field. The geometry of the magnetic field may also change significantly during a single pulse, for example during start-up, in L-H transition studies, or in scenarios where the plasma is swept over the divertor surface to spread the heat load.

Because magnetised plasmas are highly anisotropic parallel and perpendicular to the magnetic field, we want to align our computational grid with the magnetic field lines. The divertor poses special problems when the field has multiple X-points or changes significantly during a pulse.

BOUT++ is a highly optimised framework for solving systems of PDEs, particularly in tokamak edge geometry. The mesh, while sophisticated, does have some limitations. In this project you will remove some of these limitations by investigating more flexible mesh solutions and implementing them in the BOUT++ core library, making them available to the many international teams of physicists that use BOUT++ in their models, and using these new capabilities to study the behaviour of plasma in these novel configurations.

This new mesh will be made up of many curvilinear grids stitched together to conform to both the machine geometry and the magnetic field, as well as adapt to changing conditions. This will allow scientists to simulate the complex physics in these challenging environments.

While some programming experience will be very useful, you will also be taught both C++ as well as how to develop world-class research software in a distributed and international team.

The project will be mainly based in York, but there will be opportunities for travel for conferences, workshops and research collaborations, and extended visits to the USA.

The project is offered by the University of York. For further information please contact Peter Hill: peter.hill@york.ac.uk

The project may be compatible with part time study, please contact the project supervisors if you are interested in exploring this.