Professor David Larbalestier
Professor David Larbalestier is a leading world expert on superconducting materials applied to magnet applications. It’s a field to which he has devoted his whole career for over 50 years. More than 90% of all magnets, including those for MRI medical scanners and huge particle accelerators, were made with conductors optimised according to processes developed by him and his team.
If you ask those in the know to name one person who is at the top of the applied superconducting materials field, they will name David. His work has brought every superconductor made in volume today into manufacture and use. Many would say David’s success is on a par with Stuart Parkin who created magnetic read heads used in computing today.
David’s vital quality is his combination of the materials science of superconductors with the applied engineering of magnet fabrication. This interdisciplinary connection between basic science and its applications is rare and extremely hard.
Generating breakthroughs
The Rutherford Lab
David’s PhD work in the Royal School of Mines at Imperial focused on trying to understand the science of high current density superconductors. David was very fortunate to get postdoctoral work at the British High Energy Physics Laboratory. Rutherford Lab was on the Harwell Science and Innovation Campus, which then had the world's leading group developing stable, high current density superconductors for magnets.
The challenge given him by Martin Wilson was to get the just-being-manufactured-at Harwell filamentary Nb3Sn superconducting wires into magnets. Four years of work there led to the development and proving of a complex wind-react-epoxy-impregnate technology that was transferred to the Oxford Instrument company just up the road and a widespread application, now by many companies, for virtually all laboratory magnets with fields of more than 10 tesla.
A new challenge
In 1976 he was drawn to the United States by the vision of Roger Boom at the University of Wisconsin in Madison to make very large SMES (Superconducting Magnetic Energy Storage) devices to store the overnight surplus power of nuclear power plants that were then coming on grid in Wisconsin. These huge devices, designed to store 5000-1000 MWhr, had to work both technically and economically.
The challenge given to David was to make the rather expensive superconductor Nb47Ti much better at carrying current so that its cost per unit of current carried became affordable. This Nb-Ti challenge was quite different than the challenge David had faced at Rutherford with Nb3Sn, which was clearly a magnet rather than a materials problem since at the time Nb-Ti was optimised by individual black magic recipes and had hugely variable properties. It was a great topic for starting an academic career.
His first PhD student, David Hawksworth, started developing better Nb-Ti alloys and, after his PhD, went back to the UK to design MRI magnets for Oxford Instruments, designing the now standard 1.5 and 3 T magnets that so many have had scans in. The PhD and postdoctoral work that underpinned the understanding of how to double the current density in Nb-Ti in a routine and predictable way was enabled by multiple students and postdocs, a vital PhD being Christoph Meingast, now of KIT, and a postdoc, Peter Lee, fresh from his PhD at the University of Birmingham, and still a vital ASC colleague today.
With major support from the US High Energy Physics community, the understanding that generated breakthroughs in Nb-Ti current density were used both to design a huge new superconducting accelerator, the SSC (Superconducting Super Collider) and to enable the design of much more compact and cheaper MRI magnets.
More than 90% of all superconducting magnets made to date have been made of Nb-Ti, and all Nb-Ti made today uses a process worked out by David and his students and colleagues in the 1980s.
Although the SSC was cancelled in the late 1980s, many important accelerators have been built with this advanced Nb-Ti technology, most notably the Large Hadron Collider at CERN. In short, his influence on superconducting magnet technology is everywhere.
And his story starts back in the 1960s at Imperial…
The Royal School of Mines hockey team in front of the Royal Albert Hall in 1966
The Royal School of Mines hockey team in front of the Royal Albert Hall in 1966
The start of success
“I started studying at Imperial by accident,” David confesses.
I was supposed to be going to another university in the Fens, but the town seemed so small that it didn’t feel like the right fit for me. I am a Londoner and knew South Kensington well, so I applied to Imperial and got in. Besides this was London in the 60s…
Like a lot of young students, David didn’t know exactly what he wanted his future to look like. “In the beginning you’re struggling to find out who you are and where you fit.” His original plan had been to study physics. However, he had a change of heart as there was something about metallurgy that intrigued him.
What really amazed him coming to Imperial was that the much smaller metallurgy department, half that of physics, still had about 35 faculty and was very eclectic: not just metallurgists, but chemists, physicists, mechanical and chemical engineers and a mathematician too. "Metallurgy seemed to be right at the centre of the mission to make science productive, of course the central mission of the Imperial College of Science and Technology!”
He fondly remembers Weeks Hall on the north side of Princes Gardens, where he lived for two years. The metallurgy degree programme was small (“32 students who were diverse in background but not in gender since there was only one woman”) and collegial.
David describes Imperial as “one of the best places to get opportunities”. As a student, he spent two summer breaks working in industry which he found extremely rewarding. He also took part in an enrichment programme every Tuesday and Thursday lunchtime for two hours.
I think Imperial was worried that their students would only be focused on engineering or science, so they immersed us in culture. Sometimes it would be someone talking about opera. Or another day the Egyptians.
London provided a rich and then still affordable opportunity to sample all sorts of artistic life, concerts, opera, theatre, politics as well as studies. As David says, “Everything had fallen into place.” London in the 60s felt like being in “the centre of the universe.”
At the end of his undergraduate degree, other students moved on, but he knew he was happy where he was and would stay at Imperial for graduate work.
A growing fascination
Superconductivity was discovered in 1911, but it was a scientific mystery for many more decades. It wasn’t until the late 1950s that the scientific mechanism was finally figured out. However, there was still no known material that could put superconductivity to work and it remained a scientific curiosity.
In 1960 a metallurgist at Bell Labs, Gene Kunzler, blue-skied the manufacture of a Nb3Sn wire by drawing Sn inside a Nb tube, then heating it to about 1000°C to make the brittle intermetallic Nb3Sn. Amazingly to everyone, including himself, the wire was able to pass a current that exceeded 1000 amps per square millimetre, at least 100 times more than you can pass through copper. This amazing and unexpected breakthrough showed that superconductivity could be really useful for creating strong magnetic fields and many became interested in this area – including one of the professors, Hubert King, within the Metallurgy Department where David studied.
It fascinated me. There’s an image in one of the classic textbooks of a magnet levitating in a hemisphere of lead. That’s magic. When I saw this, I knew I wanted to explore it further.
Applying science to technology
What David loved about Imperial was how applying science to technology was built into its very ethos. When he was studying superconductivity, it seemed to him that the subject had “been taken over by physicists”, becoming very mathematical and degrading its capability to become useful. This led to an important mantra of David’s about superconductors: new higher temperature superconductors attract Nobel prizes, but applications require high current densities in high magnetic fields to enable machines impossible to construct with copper and iron.
Learning how to make superconductors with high current densities in high fields is the science and technology of alloying them with impurities that stuff their structure full of (the right, not the wrong!) defects to make this possible.
Defect engineering was the general topic of David’s PhD. But to make discoveries, you need the right equipment and much had to be built including bringing on a magnet made by Oxford Instruments, formed only three years earlier to build superconducting magnets. David was building a magnetometer to measure the strength of the currents possible with his materials defect engineering. But not all that is planned actually goes to plan and what happened next was decisive for his whole subsequent career.
The magnet was wound on a copper mandrel which at low temperatures produced large eddy currents when the magnet power supply was turned on, hugely distorting the magnetic field being measured by the magnetometer. Oxford Instruments offered to rewind the magnet on a more resistive stainless steel mandrel. When he got it back the magnetic distortion was stronger, not weaker – and got worse each time the magnet was cooled down again (superconductivity was then a very low temperature behaviour, operating only at about 4 K or -453 F).
It took months to work out that the stainless steel, non-magnetic as made, was becoming progressively more magnetic each time it was cooled down. This was an amazingly exciting, personal and unexpected discovery.
Taking this observation to an Institute of Metals meeting on superconducting applications, David met a magnet engineer from the Rutherford Lab, Peter Clee, who was planning an enormous stainless steel bubble chamber with an 8 tesla superconducting magnet around it. Just the conditions that could produce a hugely distorted and changing field in the forefront bubble chamber – a disaster for the measurements to be made of particle collisions.
12 months of going around the British steel industry with Peter Clee produced a huge range of samples and ways to resolve the problem and cemented his pleasure at working at the nexus of science and engineering. This introduced David into the High Energy Physics Community, a vital connection that still flourishes today.
Photo of the Jungfrau railway at 11,332ft, taken at the Interlaken M2S conference in 1988.
Photo of the Jungfrau railway at 11,332ft, taken at the Interlaken M2S conference in 1988.
New places, new discoveries
After two years in Switzerland post PhD working outside superconductivity, he was anxious to return and when a postdoc opportunity at Rutherford Lab opened up, David jumped at it and joined the superconducting magnet group there to work on filamentary Nb3Sn magnets. After transferring this technology to industry, he was interested in using superconductivity for enormous magnets, joining the University of Wisconsin in Madison in 1976 as an assistant professor, where he studied Nb-Ti for superconducting magnetic energy storage.
This new focus on Nb-Ti, previously a black magic optimised conductor, generated lots of interactions with the superconducting materials industry, especially the companies melting the large ingots used for the wires. Out of this came the opportunity to really understand how to make exquisite two-phase nanostructures and to ensure that the industrial precursors were specified so that they were reliably predictable.
These discoveries made the first truly enormous accelerator design, the Superconducting Super Collider, possible. When for budgetary reasons the SSC was cancelled, MRI magnets were ready to pull the superconducting wire industry. A decade later the Large Hadron Collider at CERN designed their magnets with the SSC conductors.
One factor leading to the cancellation of the SSC was a struggle between the condensed matter and the high energy physics communities. In 1987 the first superconductor capable of operating above 77K was found and condensed matter enthusiasts argued that huge resources should be put into engineering cuprate superconductors like YBa2Cu3O7 into applications. The discoveries excited the world and huge programmes were put in place to advance the field. But making high current density cuprate superconductors took about 20 years, which is why Nb-Ti and Nb3Sn still remain the workhorse conductors even today. However, David played a central role in the US effort to make electric utility applications possible with these new, so-called High Temperature Superconductors and slowly they are beginning to appear.
In 2006, David moved the Applied Superconductivity Center that he had directed for 19 years in Wisconsin, to the National High Magnetic Field Laboratory (NHMFL) at Florida State University. He quickly put together a collaboration with the US company SuperPower Inc to demonstrate a new high-field superconducting magnet world record using YBa2Cu3O7 coated conductor. This was the progenitor of the most powerful user magnet yet made – the 32 tesla all-superconducting magnet at the National High Magnetic Field Laboratory at Florida State University. At the R&D magnet level, David and his team have now made small insert magnets generating more than 45 tesla, a world record for any DC field.
But getting cuprate superconductors into applications is very difficult and so in parallel with the YBa2Cu3O7 work, David worked out ways to develop very high current density in a unique cuprate, Bi2Sr2CaCu2Ox, that allows high current density in a round wire, not the much less attractive tape form. This allows the same multifilament architecture as Nb3Sn with which David started his career at Rutherford lab in 1973. Oxford Instruments, now a PLC and perhaps the world’s biggest scientific laboratory magnet producer, started a decade-long collaboration that is now aiming for 25-30 tesla lab magnets, yet another example of the intimate entwining of science and applications in David’s career.
These recently renewed links with Oxford Instruments show that the long arc of his UK collaborations endures. The public interest in the magical subject of superconductivity also continues, as shown by the huge interest in the recent purported room temperature superconductor, LK-99. Although generally agreed (for now at least) not correct, the report has galvanised renewed interest in the all-things-superconducting-everywhere potential of ambient superconductivity. Given the rapidly developing power of AI for new materials discovery and property prediction, David, who consistently turns interest into reality, will move fast on any such new discoveries.
David’s research group in 1986 at the Applied Superconductivity Center with key PhD students, staff and scientists who led the full understanding of Nb-Ti superconducting wires.
David (centre) stands with key members of his group (Christoph Meingast (far left, now KIT), Lance Cooley (now Director ASC at NHMFL-FSU), Tomas Willis, unknown undergrad, David, George Stejic, Peter Lee (ASC Scientist still), Bob Remsbottom (deceased – he managed all the Nb-Ti superconducting wire procurements for the Fermilab Energy Doubler – the Tevatron), Jim McKinnell (Now HP Research), Bill Starch (ASC Lab manager both in Madison and Tallahassee still today).
The expanded ASC team in 2008, now based at Florida State University.
Globally recognised in the field
David has won numerous awards and fellowships, including the Matthey Prize for the best PhD thesis in Metallurgy and the IEEE award for continuing and significant contributions in applied superconductivity. He has been elected to Fellowships of the American Association for the Advancement of Science, the American Institute of Physics, the British Institute of Physics, the Institute of Electronic and Electrical Engineers and the Materials Research Society. He is also Fellow of the Royal Academy of Engineering, the US National Academy of Inventors and an elected member of the US National Academy of Engineering.
David with a cover feature in TIME Magazine on 11 May 1987
David with a cover feature in TIME Magazine on 11 May 1987
He has numerous Nature/Science papers and is the go-to person when the latest perspective of the field is needed. A classic example, still widely cited, is his 2001 Nature article on problems of making useful HTS conductors. His Nature paper on the highest DC field superconducting magnet is also widely cited. Recently, he co-edited the latest volume of the 2000-page Handbook on Superconductivity (CRC Press).
Inspiring the next generation
David believes good mentoring and good mentorship have been vital to his success. “You need people who make it clear they believe in you and want to give you opportunities, and to complete the cycle you need to do this too.”
David's colleagues describe him as “a truly inspiring collaborative role model for the field”. For 50 years, he has nurtured many scientists and engineers. His unstinting passion for the field is infectious, rubbing off on everyone at all levels.
Despite his successes, he recognises that learning from and supporting younger scientists is the essential path to a strong and relevant future.
I've always found people who opened doors for me and gave me opportunities. And the nice thing about that is that I have been able to open doors for people younger than me – especially students.
David has graduated 45 PhD students and hosted 40 postdocs and 25 sabbatical visitors. Half of those PhDs are in the superconductivity community in academia, industry, and government. His first PhD, David Hawksworth, joined Oxford Magnet Technology, to commercialize MRI magnet manufacture in Eynsham Oxon. He led the construction of the first shielded MRI magnets and ran the company until Siemens bought it.
Four of David’s recent PhDs are at GE Medical developing MRI. Two are at Commonwealth Fusion Systems, an MIT spin-off aiming to generate fusion power electricity before 2030.
Looking to the future
Will David retire any time soon? His response: “My 45th PhD student is graduating, and I have five other students following on. I stepped down from my position as Director of the Applied Superconductivity Center around five years ago now, but this has given me the chance to go back to teaching and to expand my research. I’m still well-funded by the Department of Energy and the National Science Foundation too.”
Of course, I would like to be remembered for having a positive impact as a scientist. But I’ve had the privilege to work with lots of young students who had the ambition to be at the forefront of the field. That impact that so many of them has made ultimately is really most important to me.
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