High-temperature superconductivity for high-field magnets and levitated trains

The specific overpromise Tom pushed back on at Kresge — high-field magnets and maglev trains "within five years."

Someone asked me a question about the new high-temperature superconductors that had just been discovered five or six years before. I said, they're fantastic functional materials, we're going to use them for detecting magnetic fields, optical sensors, things like that. But all this stuff you hear about high-field magnets — we won't see those in our lifetimes or our grandchildren's lifetimes. I got back to my office about five or six in the evening, got a phone call from a faculty member in the department. He had already heard what I'd said half an hour before. He just lit into me: you don't know anything about superconductivity. I said, Mike, I did my doctoral thesis in superconductivity, I think I know something about it.

Tom's "we won't see magnetically levitated trains in our grandchildren's lifetimes" prediction made in 1995 at Kresge Little Theater.

There's a good correlation between T-sub-c and the critical magnetic field. You go above a certain field and you lose your superconductivity. When I was working on these, I was working on some of the highest-temperature superconductors then known — worked at 20 Kelvin. The niobium aluminum had critical fields of about 30 Tesla. Anybody have a feel for a Tesla? The strongest electromagnet with an iron core is about one Tesla. An Alnico magnet is about one Tesla. Iron neodymium boron might be two or three Tesla. The strength of the magnetic field basically goes as the square of the field. So 30 Tesla is a thousand times stronger than the magnetic field you have in a regular old motor.