Posted on 31 July 2018
A consortium of four universities - Oxford, Strathclyde, Warwick and York (with York as lead in the consortium) - has secured major funding for a 5-year, £5.3M programme, with £4.3M from the EPSRC, to probe the complex science underpinning plasma turbulence in tokamak fusion reactors.
A tokamak is a ring-doughnut shaped chamber designed to contain the deuterium-tritium fuel mix at temperatures up to ten times that at the centre of the Sun. In such extreme conditions, these heavy-hydrogen isotopes can “fuse” to form helium and release large amounts of energy: fusion energy. This is the source of energy that fuels stars such as the Sun, and harnessing this energy on earth is one of the major challenges facing mankind. The heat from such fusion reactions will be used to drive steam turbines for base-load electricity production, with no greenhouse gas emissions.
While in everyday life, we normally only encounter solids, liquids and gases, at such high temperatures the fuel is in the 4 th state of matter called a plasma consisting of a “soup” of electrically charged particles. In a tokamak, such hot plasmas are held away from the reactor walls by strong magnetic fields. If this magnetic confinement is good, then high performing fusion reactors can be achieved in a compact device. In practice, the plasma in existing experiments is highly turbulent, and this degrades the confinement, requiring a large reactor to achieve the requirements for fusion.
The aim of this new EPSRC funded research programme is to understand the turbulence in a plasma confined by a magnetic field, and seek ways to lessen the effect of such turbulence.
A particular focus is on a tokamak design called a spherical tokamak. The UK pioneered the development of the spherical tokamak through the 1990’s, and now operates the world’s largest – MAST Upgrade - which is presently being commissioned by the UK Atomic Energy Authority at the Culham Centre for Fusion Energy, following a £50M upgrade. Such facilities offer potential routes to reduce the effect of turbulence. Our studies will explore these, seeking to identify a more compact approach to fusion energy, with reduced capital cost and, possibly, a faster route to fusion powered electricity for society.
CCFE Programme Director and University of York principal investigator for the programme, Howard Wilson, said: “The spherical tokamak was pioneered by Culham in the 1990s and we will soon operate the advanced MAST Upgrade device. It has a more compact geometry than the conventional JET-like tokamak and is able to contain plasma at very high pressure for a given magnetic field.
“We know that these features – compact geometry, pressure gradient, and strong flows – influence the turbulence in the plasma, but we do not have a good understanding of this in a spherical tokamak. Our university partners are world experts in this field, and by coming together with us, the consortium is well positioned to advance understanding of plasma turbulence. This will be a direct benefit to JET and to ITER development through new knowledge of pedestal physics, and, we hope, demonstrate the potential of the spherical tokamak to reduce the size and cost of commercial fusion power."