Superconductivity at 100 – The Achievements, the Promises and the New Challenges.
Superconductivity continues to fascinate both at the fundamental mechanism level and for its potential for applications. In fact Onnes came to Chicago in 1913, just two years after discovering superconductivity, with a detailed plan to make a 10 T superconducting magnet! At the centenary it may be worth reflecting on what of Onnes’ vision has worked and what, so far anyway, has not worked. In the achievement column we can put large numbers of superconducting magnets made of Nb-Ti and Nb3Sn, cooled largely by liquid helium and generating fields above 23 T. Such magnets underpin the large MRI industry (1.5-3T), high field NMR (10-23T), and large accelerators like the LHC (up to 8.5T). Both Nb-Ti and Nb3Sn are well developed conductor materials, now working close to their intrinsic limits and thus not normally discussed at the MRS, where much greater interest is shown in the cuprate high temperature superconductors. The basis of interest is for electric utility applications in temperature and field domains far from the liquid helium range accessible with Nb-base materials. Extraordinary efforts to master these complex materials have been made and great technical successes achieved. And yet, access to the expected markets has proven much harder than expected, to the point that new discoveries like MgB2, potentially much cheaper but with much less cryogenic advantage, and pnictides with higher Tc than MgB2 but lesser Tc than the cuprates, even though with much lower anisotropy, sometimes make their claims against cuprates like YBCO. And now too, new programs to discover much higher Tc, perhaps even at room temperature, are underway. Clearly many want new conductor materials with much higher Tc and Hc2 than the isotropic Nb-base materials. Yet dealing with the anisotropy and the poor grain boundary transport of pnictides and cuprates poses tough manufacturing challenges, problems unlikely to be any less significant with new materials. How to develop appropriate strategies for dealing with these complexities will be a major them of my talk.BiographyDavid Larbalestier is Frances Eppes Professor at Florida State University and Chief Materials Scientist at the National High Magnetic Field Laboratory in Tallahassee, FL. He received his PhD from the Department of Metallurgy at Imperial College in 1970. After two years in Switzerland, he returned to the Superconducting Magnet Research Group of the Rutherford Laboratory in England, working for four years on the development of multifilamentary Nb3Sn conductors and magnets, one fruit of which was the first filamentary Nb3Sn NMR magnet, for which he shared a 1978 IR-100 award with an Oxford Instruments Company team. He joined the Materials Science and Engineering Department at the University of Wisconsin in 1976, becoming director of the Applied Superconductivity Center in the College of Engineering in 1991. His group made the definitive studies of the materials processing science of the most widely used superconductor, Niobium Titanium, an achievement recognized by the 1991 IEEE Particle Accelerator Conference Award and by election to Fellowship of the American Physical Society. Professor Larbalestier has been very active in promoting collaborations uniting industry, national laboratory and other university groups, exerting a leadership role in both the Low Temperature and High Temperature Materials Superconductor Communities, achievements recognized by prizes of the IEEE (1991 and 2000) and the Council for Chemical Research (2000) for collaborations on the first HTS conductor material (Bi,Pb)2Sr2Ca2Cu3Ox. His group has been active in all classes of superconducting materials with applications prospects, including Nb3Sn, YBa2Cu3O7-, MgB2, round wire Bi2Sr2CaCu2Ox and the recently discovered pnictides. He was elected to the National Academy of Engineering in 2003 and was a member of the NRC panel (COHMAG) assessing the status and future of high magnetic field science and technology in 2004-2005. He moved to the NHMFL in 2006.