First, some background
Niobium-tin (Nb3Sn) has been used as a high-field superconductor in magnet technology since the 1960s. It is still being developed for new applications, including a planned upgrade for the Large Hadron Collider at the European Organization for Nuclear Research (CERN) in Geneva, Switzerland. This particular Nb3Sn wire is made by putting a powder made of tin into a tube of niobium. These filaments are then embedded in copper to form the final wire, which then undergoes a heat-treatment. The more current a wire can carry — a property known as its critical current density, or Jc — the better.
What is the finding?
When the wire is heat treated, the powder reacts with the tube and forms granular Nb3Sn. Small grains (with diameters of about 100 nm) carry current but large grains don’t, and larger grains typically make up about 25% of all the grains in a heat-treated wire.
Scientists discovered that varying the ratio of niobium to tin in the wire’s “recipe” prior to heat treatment resulted in significantly more small grains, which means a higher current density and a much better superconductor.
Why is this important?
Who did the research?
Christopher Segal1, Chiara Tarantini1, Zu Hawn Sung1, Peter J. Lee1, Bernd Sailer2, Manfred Thoener2, Klaus Schlenga2, Amalia Ballarino3, Luca Bottura3, Bernardo Bordini3, Christian Scheuerlein3, David C. Larbalestier1
1Applied Superconductivity Center, MagLab; 2Bruker EAS GmbH, Germany; 3CERN, Switzerland
Why did this research need the MagLab?
THE TOOLS THEY USED
This research was conducted in the Zeiss 1540 XB Crossbeam Scanning Electron Microscope at the Applied Superconductivity Center.
This study was made possible by the integrated sample preparation, metallographic imaging and electromagnetic analysis capabilities of the MagLab’s Applied Superconductivity Center (ASC). CERN has contracted for several years with the ASC to advance future particle accelerator technology using the center’s specialized analysis of both high-temperature and low-temperature superconducting materials.
Details for scientists
- View or download the expert-level Science Highlight, Evaluation of Nb3Sn superconductor for CERN's accelerator upgrade
- Read the full-length publication, Evaluation of critical current density and residual resistance ratio limits in powder in tube Nb3Sn conductors, in Supercond. Sci. Technol.
This research was funded by the following grants: G.S. Boebinger (NSF DMR-1157490); Christopher Segal (DOE/HEP-DESC0012083 & DE-FG02-07ER41451), (CERN - KE1920 and KN2713).
The PIT strand was supplied by the US LHC Accelerator Research Program (LARP), a BNL,FNAL, LBNL, and SLAC collaboration with CERN
For more information, contact David Larbalestier.