Developing and using simulation tools for the tokamak exhaust – plasma strand project

Supervisors:  Christopher Ridgers (University of York) David Moulton (CCFE).

Mainstream fusion devices necessarily involve the creation of a hot plasma at close to 100 million degrees. This plasma can be confined by magnetic fields (magnetic confinement fusion – MCF), but this poses the problem of how we deal with the flux of heat at the wall of an MCF device. The current best solution is to divert the plasma along a region of open field lines outside the hot core, the so called Scrape-Off Layer (SOL) and down onto a specially armoured target plate. This ‘divertor’ can then be specially designed to absorb the incoming heat from the core. Without advanced strategies to mitigate the heat load the target plate will be damaged, a problem which is particularly acute for reactor-scale devices.

In this project you will develop and use the advanced modelling tool Hermes-3. This is a flexible, open-source code for simulating the SOL. There are many interacting physical processes in the SOL and divertor. For example one way to reduce the heat-load on the divertor is to inject impurities to radiate the energy away. This cools the plasma and leads to a cloud of neutral gas forming a buffer between the hot plasma and the target. There are several ways in which Hermes-3 can be improved to better model the interaction of plasma, neutral gas and impurities. For example the neutral gas model currently makes the fluid assumption, which is not valid and also neglects molecules. The plasma transport model also makes the fluid assumption which should be relaxed. The transport of impurities is neglected but is important particularly in structures created by turbulence.

In this project the student will work as part of a team at the University of York and the Culham Centre for Fusion Energy to improve our modelling tools for the SOL, This will be done by developing Hermes-3 and then using this to gain new physics insights into divertor heat load mitigation. The project is flexible and can focus on any areas of this that the student is particularly interested in as well as focussing on areas that benefit the whole SOL modelling team. Interaction with experiments occurring on machines such as MAST-U is also an option as experiments take place to test our heat flux mitigation strategies. This project will give the student valuable skills in developing large scale open source user code as well as working in a vibrant team. The project is envisaged to be based at York but with extensive visits to CCFE, giving the student experience of multiple research environments.

Collaboration with CCFE is essential to this project. Presentation of work at national and international conferences is also strongly encouraged.

This project is offered by University of York. For further information please contact: Christopher Ridgers (

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

Image above: Electron temperature ion simulation of the edge of an MCF plasma.