This activity is the second year of the 40T Superconducting (SC) Magnet project at the National High Magnetic Field Laboratory (NHMFL). It describes high-temperature superconducting (HTS) test magnets and related work necessary to validate technology advances sufficient to complete the conceptual design of a 40T SC magnet. Both a 40T SC magnet and a subsequent 60T Hybrid magnet were listed as national priorities in the 2013 National Research Council report on High Magnetic Field Science and Its Application in the United States. This 40T SC magnet will enable the United States to further and decisively advance its leadership in SC magnets via another great “superconducting leapâ€, exceeding in magnitude even its recent achievement of 32T in an all-superconducting magnet. Upon its commissioning, the 40T SC magnet will become a flagship in the NHMFL’s suite of high-field magnets that serve its growing user community. The NHMFL presently provides >11,000 days of magnet time annually to >2,000 users, including ~700 Ph.D. students and ~300 postdocs, for high-magnetic-field experiments. This research has resulted in 3,180 refereed papers in the scientific literature from 2012 to 2018. The new magnet will roughly double user access to DC magnetic fields exceeding 36T. The 40T SC magnet will be highly featured in the NHMFL’s education and public outreach programs that interact annually with >10,000 K-12 students via classroom outreach and lab tours and >10,000 visitors of all ages to the NHMFL’s annual Open House. The technology development resulting from the realization of this 40T SC magnet will set a benchmark for high-field magnets connected with frontier capabilities in high energy physics, fusion, X-ray and neutron facilities, nuclear magnetic resonance, and magnetic resonance imaging installations.
The 40T SC magnet will be constructed using REBCO (Rare Earth Barium Copper Oxide) tape conductor similar to that used for the NHMFL’s present world-record 32T SC magnet. However, the 40T SC magnet will feature an approximately ten-fold increase in the stored energy of the HTS coils, which places priority on developing active quench protection and reducing coil volume. Two alternative conductor technologies are thus being pursued: 1) Insulated REBCO (I-REBCO), which exploits comparatively a much better understanding of quench behavior gained from the 32 T SC magnet project; and 2) No-Insulation REBCO (NI-REBCO), which shows potential to attain higher current density and dramatic compaction of coil volume as demonstrated by the NHMFL’s 2017 test of a coil 50mm long and 34mm in diameter that generated a record of a total field of 45.5T in a 31T background magnetic field (generated by an NHMFL resistive magnet). Reliable operation under cyclic loading and during quench are core development goals for both alternatives. The NHMFL developed key insights on quantifying strain due to screening currents in REBCO coils, which opens paths to ensure sufficient fatigue life. Advanced quench protection I-REBCO technology operating at higher current density is underway by exploiting recent improvement in commercial superconductors and super-capacitors. Development in NI-REBCO technology focuses on controlling contact resistance and active quench protection. Either of these developments may be employed in a future 60T hybrid magnet. When complete, the 40T SC magnet will provide a very low noise environment for experiments lasting days at a time, surpassing present-day powered (resistive and hybrid) magnets. Advances in experimental capabilities will include quadrupolar nuclear magnetic resonance, specific heat, and multi-gate tuning spectroscopies, as well as systematic high pressure measurements and systematic dimensionality crossover studies by repeated sample exfoliation. These frontiers in quantum matter include high temperature superconductivity, Ising superconductivity, re-entrant superconductivity, exciton condensation, non-Abelian quasiparticles, topological matter in its myriad forms, and the mysteries surrounding the Mott transition as the canonical many-body quantum phase transition.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
