A Superconducting Permanent Magnet Motor has been built at Cambridge University's Engineering Department in collaboration with Magnifye Ltd.

Magnifye is developing the technology to produce the strongest permanent magnets in the world. Using rare earth superconductors Magnifye's technology enables these to be magnetised to fields orders of magnitude greater than that available from ordinary permanent magnet materials such as NdFeB and SmCo. Magnifye has developed a heat engine which converts thermal energy into currents of millions of amps. The thermal energy is used to create a series of magnetic waves which progressively magnetise the superconductor much in the same way a nail can be magnetised by stroking it over a magnet.

A Superconducting Permanent Magnet Motor

As long as the superconductor stays cold, the currents will flow uninterrupted, providing powerful, stable, shapeable magnetic fields for a wide range of applications. These powerful magnets can be small enough to fit in the palm of the hand and large enough to power a train or a cruise liner.

Engineers at the University of Cambridge have also used new techniques to manufacture high-temperature superconducting materials, producing samples that can carry record quantities of electrical current for their type and size. he breakthrough has improved the effectiveness of yttrium barium copper oxide (YBCO) and a related family of superconducting materials. It raises the prospect of more powerful and affordable samples that could have huge benefits in a number of fields.

At present effective superconductors are often expensive and difficult to mass-produce. The Cambridge research could be a step towards resolving this, by providing the basis for the development of more powerful samples that can be manufactured using a commercially compatible process.

That would drive down the production costs of machines that rely on the materials. MRI scanners, for example, which can cost around £1.5million each, could eventually become a common sight in GP's surgeries, helping to improve accurate detection and diagnosis of problems ranging from twisted knees to brain tumors.

The Cambridge team have developed a technique to manufacture large single grains of bulk superconductors that involves initially heating the material to a temperature of 1,000 degrees C, causing it to part-melt. In a series of experiments, various elements, such as depleted uranium, were then added to the chemical composition of the superconductor to generate artificial flux pinning sites within the single grain.

When the material cooled and reformed, these added materials retained their integrity and formed physical obstacles that form direct the motion of magnetic flux lines, enabling larger currents to flow.

In addition, the team developed a technique for fabricating large, single grains of bulk superconductors in air, using a new type of seed crystal that they have also patented, which enables much more scope for optimising the partial-melt process. Together, these techniques led to the production of samples far more powerful than those fabricated by more standard techniques, which exhibited record energy densities and magnetic fields for their size.

"The properties these samples exhibit could in time offer huge commercial potential by improving or reducing the weight and size of applications such as energy storage flywheels, magnetic separators, motors and generators," Professor Cardwell added.