Ask a Scientist: What’s a superconductor? How does it work?

Justin Schwartz is department head and Kobe Steel Distinguished Professor at N.C. State’s Department of Materials Science and Engineering. Here, he explains the science between superconductors and superconducting materials. Questions and answers have been edited.

Q: What is a superconductor and how does it work?

A: First, you have to understand that materials can be divided into many categories, depending on how they conduct electricity. Insulators, like wood or plastic, hold tightly to their electrons so electrical current cannot flow through them. Conductors – metals like copper or aluminum – allow electrical current to move easily, but a few electrons get lost along the way. Superconductors are special materials that can transport electrons without any loss, meaning they can conduct electricity perfectly.

Superconductors have another exceptional feature known as “perfect” diamagnetism, which means they repel the magnetic field that normally penetrates other materials. In other words, magnets can literally float above superconductors. But there are limitations. Superconductivity only occurs at very low temperatures, about 225 degrees below zero (Fahrenheit) or colder. Therefore, these materials have to be stored in frigidly cold liquid helium or liquid nitrogen; otherwise, they lose their amazing properties.

Q: How is this technology already being applied in our everyday lives?

A: The primary place people experience superconductivity in their everyday lives is through magnetic resonance imaging: MRI, a procedure commonly used to diagnose medical conditions. MRI scans have primarily been used to assess orthopedic injuries – I’ve had my knees and shoulders imaged a few times – but recently its application has expanded to the brain and other organs.

Superconductors are also used in the high-energy physics colliders like the Large Hadron Collider operating outside of Geneva at CERN, the European Organization for Nuclear Research. This device has a large number of superconducting magnets, both for guiding the particle beams that collide, and also as part of the detectors used to figure out what happens in the particle physics experiments.

Q: What are some futuristic ideas for the use of superconductors?

A: There has been a lot of progress in recent years for more superconducting applications. One area that gets a lot of attention is generators for wind turbines. Many feel that superconducting systems have particular advantages for such applications. Another area is in high-speed rail. The fastest train in the world is a magnetically levitated – or “maglev” – train in Japan that recently broke its own speed record. This train is based upon superconducting technology.

Another future application is in fusion power reactors. The ITER reactor currently under construction in France uses a number of very large superconducting magnets to confine and control a “plasma” fuel source. ITER alone is using hundreds of miles of superconducting cables. If ITER succeeds and the technology is transformed to commercial power reactors, the amount of superconductors required will be vast.

Perhaps the most futuristic use of superconductors is for space exploration. The magnetic field from large magnets can be used to shield people in space from space irradiation. But this application is a few years off.