Modelling kinetic effects on the heat exhaust in high power tokamaks (plasma strand project)

Supervisor/s: Dr Chris Ridgers (University of York) and Dr Ben Dudson (University of York)

To achieve conditions where substantial energy output is obtained via fusion reactions a DT plasma must be heated to hundreds of millions of degrees. Containing this plasma for a long time is essential for a viable power plant concept. Heat transported to the edge of the device must be kept within limits that can be withstood by the materials comprising the wall. In state-of-the-art tokamak devices this is achieved by using the magnetic topology inside the device to direct the exhaust plasma onto an armour-plated divertor. Even adopting this technique, further mitigation strategies will be required on next generation higher power output experiments such as ITER to keep the heat flow to the divertor within tolerable limits. There is currently no solution to this problem for power plant designs such as DEMO and other possible more compact power plant designs (STEP, ARC). Handling the power exhaust is a major problem which must be solved if these designs are to be realised.

Current state-of-the-art modelling of strategies to control the power exhaust are based on fluid models which assume local thermodynamic equilibrium (LTE). In the extremely hot plasma in a fusion decvice this cannot be assumed. We have recently pioneered including new non-LTE (kinetic) models  into tokamak edge simulations and have seen significant departures from previous results obtained for ITER. The importance of these kinetic effects is only expected to grow on power plant scale devices. Building on these preliminary results the student will fully explore the effect of previously ignored non-LTE physics on the heat exhaust in high power tokamaks paying particular attention to the effect on strategies to mitigate excessive heat loads on the divertor such as detachment. Here a neutral gas in puffed into the divertor region to radiate away the heat. Kinetic physics may significantly affect the window of parameters over which this is effective.

The project will be mainly computational with some analytical theory required to test the new kinetic models. While experience using simulation codes is helpful it is not required.

While the project will be based at the York Plasma Institute, short visits to the Culham Science Centre are encouraged.

The student will develop programming and computing skills as well as the skills to handle large data sets – highly-valued in today’s knowledge based economy. The drive towards a working fusion reactor is inherently a collaborative endeavour and we envisage ample opportunities to collaborate with scientists (and students) at other universities, large fusion laboratories and in industry.

This project is offered by University of York. For further information please contact: Dr Chris Ridgers (christopher.ridgers@york.ac.uk) or Dr Ben Dudson (benjamin.dudson@york.ac.uk).