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Details of Grant 

EPSRC Reference: EP/N023846/1
Title: The influence of magnetic geometry on the plasma edge region of future fusion reactors
Principal Investigator: Lipschultz, Professor B
Other Investigators:
Dudson, Dr BD Gibson, Professor K
Researcher Co-Investigators:
Project Partners:
Ricardo Group Swiss Federal Inst of Technology (EPFL)
Department: Physics
Organisation: University of York
Scheme: Standard Research
Starts: 01 October 2016 Ends: 31 March 2020 Value (£): 794,813
EPSRC Research Topic Classifications:
Fusion Plasmas - Laser & Fusion
EPSRC Industrial Sector Classifications:
Energy
Related Grants:
EP/N024109/1
Panel History:
Panel DatePanel NameOutcome
18 Feb 2016 EPSRC Physical Sciences Physics - February 2016 Announced
Summary on Grant Application Form
Je-S summary: Developing a portfolio of energy producing solutions is imperative to advance the economy, keep society functioning and to fight the advance of climate change. Commercial fusion will play an important role as part of that portfolio when technical challenges are overcome, having the ability to provide a low-carbon, essentially limitless, steady source of energy on a large scale, with a small land footprint.

Arguably the biggest challenge to the magnetic fusion energy concept is how to safely channel the reactor heat exhaust to the surrounding material surfaces. The fusion reactions occur between ions in the hot fusion core that are at a temperature ~ 100 million oC. This provides enough energy for the positively charged nuclei to overcome their electrical repulsion and come close enough for the attractive nuclear force to take over. The two ions then bind to form a new nucleus with less mass than the original two ions, releasing energy. The hot plasma is contained within a magnetic 'bottle', called a tokamak, which has the shape of a torus. Exhaust energy and particles, which leak out of the magnetic bottle in steady state, are diverted away along magnetic field lines to remote material surfaces (termed 'divertor targets') designed to handle the resulting high power densities. The excellent confinement of energy within the magnetic bottle necessary for fusion energy production results in a narrow channel of exhaust power flowing to the divertor targets which, for a tokamak of radius ~ 5m, has a channel thickness of order 1 mm. The resulting heat flux flowing along the magnetic field to the divertor target likely approaching 25GigaWatts/m2. This is about 500x times the heat flux of an arc welder and 2500x what the engineering limits of steady state heat transfer to a solid material allows (10MegaWatts/m2).

We employ several methods to reduce this heat flow to surfaces to below engineering limits: a) The simplest is to arrange the angle of the target to the heat flux to be small, spreading the divertor heat over a larger area, reducing the peak heat flux by x20; & b) More significantly, we encourage light (power) to be emitted from the plasma. We also utilise other atomic processes to remove energy, momentum and even particles from the plasma in a process we call 'detachment'. Detachment has been the main process to reduce the heat flux to the target, but more reduction is needed for a viable reactor-scale device.

The goal of this research project is to evaluate how modifications of the magnetic fields and geometry in the divertor target ('alternative divertor configurations') region can further enhance the power removal properties of the plasma & reduce the heat fluxes reaching divertor surfaces below the engineering limit. In the research proposed we will: a) test our model predictions that alternative divertor configurations remove more heat from the plasma & better control the detachment processes using data from existing and new diagnostics we develop; and b) study both the dynamics of how the plasma is cooled through the processes mentioned and the sensitivity of the detachment process to external controls.

This project will promote the UK into a world-leading role in the area of fusion reactor divertor physics research through development of key knowledge and research capabilities within the UK. Indeed, we will contribute unique results to the upcoming EU decision of what the appropriate divertor solution is for commercial reactors, reducing the time to a demonstration fusion power plant. The proposed work will also accelerate fusion research at the £50M upgrade to the MAST tokamak at Culham, where the first (worldwide) embodiment of the so-called 'super-x' alternative divertor topology will occur. By the UK playing a key role in achieving fusion the country will benefit economically from commercial applications as well as having an essentially limitless, steady source of clean energy into the future.
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Organisation Website: http://www.york.ac.uk