There is a hoary old joke that nuclear fusion power is a decade away, and will always remain so. It would be a fool who bets his life savings on when the first viable fusion reactors come on-stream, but a recent advance in plasma physics and fusion research indicates that it may be sooner rather than later. We should certainly hope so, for fusion power is our best hope of providing on a sustainable and environmentally friendly basis the electrical energy required for a crowded planet in which everyone can realise their dream of a life of opulence and blameless bourgeois domesticity.
The latest sign that power from nuclear fusion could soon be on the cards is provided by work carried out at the Joint European Torus, the world’s largest magnetic confinement plasma physics experiment, sited on an old Royal Navy airfield in Culham, Oxfordshire. In a paper published today in the journal Nature Communications, a team of Swiss and UK physicists led by Lausanne-based Jonathan Graves shows how it is possible to control certain plasma instabilities in tokamak reactors, and thereby overcome some of the more serious problems that have long dogged fusion power.
Plasmas are extremely hot, ionised gases, and in fusion reactors they are confined within doughnut-shaped vessels by powerful and power-hungry magnetic fields. The problem is that confining such highly energetic fluids so that they do not come into contact with reactor vessel walls is an huge technical challenge. Plasmas are inherently unstable beasts, whether they be of the engineered type, created, confined and manipulated in the laboratory, or naturally at large in Earth’s space environment and wider cosmos.
With fusion plasmas, a variety of physical forces and instabilities oppose efforts at confinement within reactor systems. Magnetic instabilities can sharply reduce reactor efficiency, to the degree that the input power required to sustain the reaction is greater than the output from the reactor.
What Graves and his colleagues have done is exploit a recently discovered theoretical effect in magnetohydrodynamics – the physics of electrically conducting fluids – and with a technique known as phase space engineering show how to avoid the kind of disruptive tearing instabilities common to fusion plasmas. This breakthrough could lead to major performance advances in the next generation of research reactors, such as the international ITER project currently under construction at Cadarache in the south of France.
Graves et al., “Control of magnetohydrodynamic stability by phase space engineering of energetic ions in tokamak plasmas”, Nature Communications (2012)