Courses: P4, P14, P16, P19
A superconducting disk is wrapped in tissue paper (we tried many things and this worked best!). It is cooled with liquid nitrogen (the tissue makes this take a little longer than otherwise, but holds enough nitrogen and has enough insulation to keep the disk at superconducting temps for a few minutes), placed on a mobius strip shaped track of magnets, and given a push. It will zip around the track for some time before warming up and falling off. This track uses 1800 neodymium magnets, arranged such that the direction of the field never changes as the train moves along the track. Place a piece of magnet viewing film on the track to illustrate this.
To cool the "train," place it in a small plastic box and set it on the track. Then pour LN2 into the box to cover the train. You'll need to add additional LN2 as some boils away, before the train reaches temperature. This has to be done on the track since the flux gets pinned in place when the superconducting transition occurs. However, this means that once cooled it won't want to slide off the track so you can remove the box of LN2. Wear gloves and be careful of splashes; grab the box and the train with two hands, and slide sideways off the track. Once removed, set the box of LN2 down and replace the train onto the track -- it will snap into place with surprising force! Give it a push and away it goes.
Setup: Pour nitrogen into a smaller thermos to make it easier to pour into the plastic box. Provide cryogenic gloves and splash goggles. Provide magnet viewing film. When taking in and out of storage, be careful the track does not come into contact with the metal shelving, or the metal door!
