Master in a spin
The Master, Nicky Padfield, demonstrated the superconducting levitating platform during Professor David Cardwell's lecture 'Bulk superconductors: revolution or red herring?' on 17 November.
The demonstration showed how superconductors can be used to make a low friction bearing that both levitates and stabilises - with no frictional losses.
Professor Cardwell said: "There's no external energy input; it's an entirely passive situation. There's no active control, and there's no electrical driver."
The superconducting levitating platform has a load capacity in excess of 100 kg, and was constructed by Ben Cator, one of David Cardwell's students, as part of his project work.
The rotating platform has two tracks of powerful rare earth magnets underneath it. These tracks are supported by over 30 superconducting bulk samples. The magnetic field generated by the magnet track varies in sign across the track but remains constant along its length. This means that the tracks can rotate, as this does not change the magnetic field seen by the superconductor, but cannot move sideways.
There are no frictional losses in this system (other than air resistance to the rotation of the plate), although imperfections in the homogeneity of the magnetic field generated by the individual rare-earth magnets does cause a small amount of resistance to rotation, which eventually stops the platform rotating.
A similar, but much more refined, bearing is used in a superconducting flywheel system made by Boeing.