High Radiation Resistant, Low Cost Superconducting Strands for Fusion Magnet Applications

One lesson learned from ITER and applicable to future fusion systems like DEMO is the need for superconductors that are more economical and stable to replace present ITER superconductors Nb3Sn and NbTi because of rising cost of liquid helium and Nb. In the near term, very formidable technological and manufacturing issues likely mean that YBCO, BSCCO, or Fe-based superconductors would not be sufficiently cost effective or available in long enough piece-length, or otherwise be counted on to fill the need. Current 2nd generation Magnesium Diboride (MgB2) superconductor already has the stability and performance level meeting, and potentially exceeding the requirements of fusion magnets that operate in medium fields and temperatures. With expected further advances in materials, and technological and engineering aspects, combined with commercial-scale manufacturing capability enabled by Hyper Tech’s continuous tube forming and filling process, MgB2is arguably the only superconductor that could offer the performance of Nb3Sn at NbTi pricing in medium term, and therefore is a viable and logical candidate for incorporation into future fusion systems. We are proposing approaches aimed at realizing the potential of next generation MgB2 wires for fusion magnet applications: 1) Using low activation 11B-enriched precursor material in fabrication of MgB2 wires to enhance resistance against neutron irradiation. 2) Improving high-field engineering critical current density in MgB2 wires to a 8,000 A/mm2 benchmark at 5T-15K by adding a catalyst to promote MgB2 formation to maximize the area fraction of the reacted MgB2 layer, and using boron powder doped with Dy2O3 to enhance flux pinning. 3) Using modified strand architecture and wire processing technology to fabricate 2nd generation MgB2 multifilament wires of high copper content, and of reduced effective filament diameter for improved thermal and magnetic stability. 4) Incorporating the advanced strands developed into a prototype cable patterned after a proposed design in a future fusion system.