superconductivity: advices for experiments

You will find gathered on this page various information which will allow you to make experiments on the superconductivity including videos. The site supraconductivite.fr also proposes many useful information.

Attention, these experiments require the use of liquid nitrogen and powerful magnets, potential sources of danger. Take all precautions and, if possible, train initially with people who are used to handling liquid nitrogen.

Magnets

The magnets called “neodymium” are the most powerful and make the experiments more impressive, they are the magnets we use. Warning: these magnets can be dangerous when they are big (more than about 1 cm cube), because the forces they create become important.  There are many resellers of magnets on the internet. We use the site e supermagnet  that allows the payment of the orders by administrative order, after delivery, but we did not test all the resellers, far from it.

Superconductors

Here are the suppliers we use for our experiments. This list is not intended to be exhaustive, and does not claim to regroup the best sources of superconducting samples, only those we use (and which accept orders following the rules of French universities).

Superconducting Samples for Meissner Levitation
We buy them from can-superconductors.com. These samples are polycrystalline, and the vortices are weakly pinned. Magnets that can levitate on such pellets should be light (for example, a disc 1mm thick and 10mm in diameter, as on the video).

Superconducting samples for strong-pinning levitation

To produce trains for strong-pinning levitations, monocrystalline samples are required. The levitating magnets are then “locked” in position and can be heavier. These pellets are more expensive (up to several hundred euros depending on size).

We buy our pellets from ATZ. The standard thicknesses are 12 mm, but we realized that 6 mm samples were suitable for our needs: when ordering, we therefore ask that the pellets are cut in half in the direction of the thickness, so as to get two pellets for the price of one.

Here we ask for our trains:

1 HTS YBCO element, melt textured tile, single grain
Composition: Y1.65Ba2Cu3O7-x – bulk
OD 30 mm x > H 14 – 15 mm
Cut to OD 30 mm x H 6 – 7mm (2 pcs., passivated for protection)

The company can-superconductors.com also offers such pellets, but we have not tested them.

• Samples for intermediate-pinning levitation

These pellets pin the vortices sufficiently to let a fairly heavy magnet levitate (30 mm diameter and 5 mm thick) at a reasonable distance (1 cm), but the pinning isn’t too strong so that the magnet can be easily removed by hand, allowing easy and impressive demonstrations (but complicated to explain in detail!). We buy from ATZ. The standard thicknesses are 12 mm, but we realized that 6 mm samples were suitable for our needs: we therefore ask that the pellets are cut in half in the direction of the thickness, so as to get two pellets for the price of one. The quality of these pellets varies from one time to another, because they are fallouts of the production.

Here is what we ask for our demonstrations:

1 piece of HTS YBCO elements
melt textured tile, seeded / polycrystalline material
Composition: Y1.65Ba2Cu3O7-x – bulk
Medium quality for levitation effects
OD > 40 mm x H 10 – 12 mm

Cut to OD > 40 mm x H 5 – 6 mm into 2 pieces, and passivated for protection.

• Samples for resistance measurements

We buy them from ccan-superconductors.com. These samples have electrical contacts already prepared, and have a transition temperature around 100 K. The practical details allowing this measurement as well as the necessary electronics are described in the project “Ohm’s law in a superconductor”