Martin Wood: Superconducting magnets

Martin and Audrey Wood discuss the early development of superconducting magnets.

AW: We got into superconductors because we were at a conference. Here we were, already making a high magnetic field and there were very, very, very few other companies in the world making high magnetic fields, almost none. And there we were, making, I agree, only about one magnet a year, these big copper ones, and we went to a conference in MIT and Martin had to give a paper on the latest development in magnets that he had done. And at that conference the superconductors really arrived. They’d been working on them for a few months in America and getting a bit more and more excited, and we’d heard little snippets of news about them, but it was at that conference it suddenly became clear that the future for high magnetic fields lay with superconductors. And we decided that night, on the New York subway, to try this new technology. So we jumped in, into this, knowing nothing about cryogenics virtually, and – but the Clarendon then knew quite a lot - and it grew from there. Because as soon as we got back to England we ordered a pound of this stuff and Martin wound this magnet.

MW:  Before superconductors when you needed a lot of power to make the same magnetic field, in Clarendon lab where I used to work, in the winter when the – we had a twenty megawatt power supply in Oxford that was not on the National Grid then, had a twenty megawatt generator in the power station down near the railway station. And one was strictly limited in how much power you could take out of that, particularly in the winter when it was cold and there was a lot of heating on everywhere, we used to be able to work from seven o'clock at night till seven o'clock in the morning. Now with the superconductor you don’t take any power worth counting off the system, and it just made life for research people in physics so much easier, being able to do it day and night with no big power in. Since superconductors have come, you had the materials through which electricity can flow without any resistance. So you can have a high magnetic field when you’re simply using something like a car battery, or nowadays a more sophisticated small electronic power supply. So you finish up with magnets like this, which can produce quite a high magnetic field in the middle, using a relatively small power supply as long as it’s kept cold. So this, I hold it in my hands now, but this is supported on these three hooks in fact by supports from down in the middle of a big container full of liquid helium.

AW: And we put it in the New Scientist, a little paragraph in the New Scientist, and it was really a case of people beating a track to our door ‘cause lots of people wanted to do research in high magnetic fields and they couldn’t afford the huge setups that they all needed for these bigger copper magnets.  And so we ordered, we got orders by that Christmas, I don’t know, it was about April that you wound it, and we put it in the New Scientist.  By Christmas we had about a dozen enquiries and at least five orders, and we ordered 5 pounds of superconductor which was very expensive then.  And, blow me; it was not nearly as good as the first lot.  If this lot had been as bad as that lot we might not be here today [laughs].

MW: It was just luck the first hundred feet or so, first hundred metres, worked perfectly the first time.

AW: it was more than that I think but still.

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