Is the superconductor theory flawed?

11 Apr 2016

This image of a magnet levitated over a high-temperature superconductor array shows rectangular TFMs (black) levitating a heavy ferromagnet (silver) above a container of liquid nitrogen, via Weinstein/University of Houston

Physicists in the US claim to have found errors in the superconductor theory, with the use of trapped field magnets (TFMs) no longer thought to be as impractical as before.

The superconductor theory has been accepted for more than 50 years, ever since a General Electric scientist developed the ‘Critical State Model’. However, now University of Houston physicists report finding a chink in its ‘theoretical armour’, discovering “significant deviations” in their studies.

Superconductors present zero resistance to electrical circuits, storing energy for long periods of time. Those that store magnetic energy – known as “trapped field magnets” or TFMs – can behave like a strong magnet.

The theory was developed by a scientist called C.P Bean, who found that the performance of a device based on magnets improves as the strength of the magnet increases. This is true up to the square of the increase, so if the magnet is three-times stronger, the device performs up to nine-times better.

But Roy Weinstein and his colleagues have found a key problem in the original theory, namely that the spatial distribution of field increases appear more immediate than Bean thought.

Controllable, repeatable

“Great increases in field occur suddenly, in a single leap, whereas Bean’s model predicts a steady, slow increase,” Weinstein said, with his new findings showing that this ‘unexpected’ behaviour is actually controllable and repeatable.

To reach ‘superconductor’ level, the pulsed field must be typically more than 3.2 times as strong as the TFM’s field. Weinstein said that with these latest findings, a rate of 1.0 is all that is needed.

In terms of applications for their discovery, the researchers suggest the ability to replace a $100,000 low-temperature superconducting magnet in a research X-ray machine with a $300 TFM, or possibly replace a motor with one that is a quarter of the size of an existing one.

Elsewhere, researchers working on ways to create superconductors at higher temperatures than the accepted -135ºC have made a breakthrough.

A research team discovered that only half the atoms in some iron-based superconductors are magnetic, giving a clearer understanding of magnetism in general.

Gordon Hunt was a journalist with Silicon Republic