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.
The Ockham Lecture series
The Merton College Physics Lecture (the Ockham, or Occam, Lecture, so named in honour of one of the greatest—if unattested—alumni of the College and of his philosophical principle of intellectual discipline) started in 2009 and is held once a term. It is organised by the physics tutors of the College to promote both intellectual curiosity and social cohesion of the Merton Physics community.
Attendance is by invitation: All Merton physicists (and sympathisers!) belonging to the three Common Rooms (JCR, MCR and SCR) are invited, as are the Old Members. Their guests are also accommodated, space permitting.