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RN23 - Conductors from Superconductors

Conductors from Superconductors

David C Larbalestier and Peter J Lee

Applied Superconductivity Center
National High Magnetic Field Laboratory
Florida State University
2031 East Paul Dirac Drive
Tallahassee, FL 32310 USA

Abstract - Kamerlingh Onnes came to Chicago in 1913, just two years after discovering superconductivity, with a detailed plan to make a 10 T superconducting magnet!   He recognized very clearly the central advantage of superconductors for generating strong magnetic fields – their ability to make compact windings operating at current densities of many hundred A/mm2 without dissipation.  His Hg wires passed 1000 A/mm2 – but sadly only in self-field, and the dream was put away.  Fifty years of confusion over the distinction between positive and negative surface energy superconductors ensued that was blown away only in 1961 when, to great surprise, Nb3Sn was found to superconduct while carrying 1000 A/mm2 at almost 9 T.  Within 2 years, Onnes’s dream was fulfilled and, within 10 years, Nb-Ti and Nb3Sn research superconducting magnets became common, based on sub-divided conductors composed of fine, twisted and decoupled superconducting filaments.  At first for science, above all for accelerators, magnet applications pulled the technology powerfully and then in the late 1970’s MRI emerged as the anchor of the superconducting wire industry.  Today a profitable industry making NbTi and Nb3Sn conductors exists on multiple continents.  MgB2, REBa2Cu3O7-x and the two BSCCO compounds, Bi2Sr2CaCu2O8-x and (Bi,Pb)2Sr2Ca2Cu3O10-x are vying to add to the mix.  Some interesting stories of how this technology emerged and how it might still change will be presented to remind us that progress is never smooth and steady, but rather episodic and sometimes disruptive.

Keywords - Low- and high-temperature superconductors, technical superconducting wires, critical currents and critical fields, superconducting magnets, LHC


Plenary presentation (3-H-4) given on September 21, 2011 at SCC (annotated slides & videos)
Submitted to ESNF February 02, 2012; accepted February 12, 2012. Reference No. RNP23; Category 2,5,6,11.