Fusion Energy with a Twist

A ball of plasma

Abstract

According to Ampere's law, curl B = J, an electric current produces rotation of magnetic field lines. For instance, if a current is made to flow along a straight magnetic field, it acts to twist the field lines into helices. In 1951, Lyman Spitzer, a legendary Princeton astrophysicist, discovered that magnetic field lines may actually wind around each other even if J=0. Most physicists are astonished by this little-known result, which was later rediscovered in other guises, such as the "Berry phase" in quantum mechanics. Spitzer proposed to use it as a key to achieve fusion energy in the laboratory, where it provides the only practicable way to insulate a 100-million-degree plasma from the surroundings in steady state. His idea is now put to a billion-euro test by the Max Planck Society in the Wendelstein 7-X experiment, which has just started operation. In this lecture, I will give a simple account of Spitzer's insight and describe this latest experiment in the worldwide quest for fusion energy.

About the author

Born in Swedish Umeå in 1967, Per Helander studied physics at Chalmers University of Technology in Gothenburg. After taking his PhD on the dynamics of fast ions in fusion experiments of the tokamak type in 1994 and working as a visiting scientist at Massachusetts Institute of Technology in Cambridge (USA), he joined the theory department at Culham Science Centre in Abingdon (Great Britain) in 1996. He also served as an adjunct professor at Chalmers University of Technology from 2002 till 2005. In 2006, he was appointed Scientific Fellow at the Greifswald Branch of Max Planck Institute of Plasma Physics where he heads the department "Stellarator Theory". In parallel he was appointed to a chair for theoretical plasma physics at the University of Greifswald. His personal research interests include most aspects of stellarator and tokamak physics, in particular kinetic theory, as well as general questions in plasma physics.

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