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Qiang Li1

1, Brookhaven National Lab, Upton, New York, United States

Cuprate (RE)Ba2Cu3O7-d (RE = rare earth elements) high temperature superconducting (HTS) cables offer powerful opportunities for increasing capacity, reliability, and efficiency of the electricity grid. HTS coils can provide an alternative to rare-earth permanent magnets used in rotary machines and generators. Here, we present our recent studies carried out at Brookhaven National Laboratory’s Tandem Van de Graaff facility. We demonstrated a roll-to-roll irradiation process on production-scale cuprate HTS coated conductors that resulted in uniform enhancement of critical current up to 77 K at the dosage and ion energies readily accessible with commercial electrostatic generators. While great progress has been made in the applications of cuprate HTS, iron-based superconductors have attracted a great deal of interests in both fundamental physics and potential applications. We have grown iron-chalcogenide superconducting films on various single crystal substrates and metal substrates with enhanced transition temperature Tc, and carry high critical current density Jc.1,2 Recently, we developed a new route for simultaneous increase of Tc and Jc in iron-based HTS films by low-energy proton irradiation. Extensive transmission electron microscopy analysis provides direct atomic-scale imaging of cascade defects and the surrounding nanoscale strain field produced by low-energy proton irradiation.3 Tc is enhanced due to the nanoscale compressive strain induced by the irradiations and proximity effect, whereas Jc is doubled under zero field at 4.2 K through strong vortex pinning by the cascade defects and surrounding nanoscale strain. At 12 K and above 15 T, one order of magnitude of Jc enhancement is achieved in both parallel and perpendicular magnetic fields to the film surface. This robust, scalable and practical route opens up the possibility to improve both Tc and Jc in all superconductors [Ref. 1) Rep. Prog. Phys. 74, 124510 (2011). 2) Nat. Commun. 4, 1347 (2013). 3) Nat. Commun. 7, 13036 (2016).]

The author acknowledges the funding support from US DOE Office of Science, Materials Sciences and Engineering Division, and the US DOE, Advanced Research Project Agency-Energy, and collaborations with T. Ozaki, M. W. Rupich, L. Wu, W. Si, and V. Solovyov.

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