Simple Sandpile Model Helps Solve Problems Of Fusion Power

This result is important because it demonstrates a comparatively simple link between space, astrophysical, and fusion plasmas and their overall confinement properties, and is a clear and welcome example of the unity of physics.

Nuclear fusion harnesses the same processes that generate the sun's energy - plasma fusion. This plasma gas is too hot to be contained by a conventional vessel so magnetic fields, shaped like a US donut (tokamak), are used. Temperatures hotter than the centre of the sun have been sustained for tens of seconds in a plasma volume of tens of cubic metres but the challenge is then to keep this small artificial sun burning and confined in its magnetic bottle.

Intriguingly, fusion plasmas have been found to self organise under certain conditions to give exceptionally good confinement. This superstable 'H mode' is not well understood but may hold the key to creating a stable fusion plasma power generator.

The University of Warwick and the Culham Science Centre team used sandpile modelling, as many other research teams have, on the problem of stable plasma confinement as many have thought that there was a link to self organisation - the ability of complex systems to re- organise internally to choose a preferred state - as it is a ubiquitous phenomenon in nature. They found a numerical 'sandpile' that mimics the self organisation of the fusion plasma to its superstable 'H mode' and that 'sandpile' model is simple enough to allow detailed theoretical analysis.

A paper, detailing their success in using this approach will be published in Physical Review Letters, on 19th March 2001. This work was supported at Warwick by the Particle Physics and Astronomy Research Council, and at Culham by EURATOM and the DTI.