VISITING PROFESSOR Leonardo Civale is a Fellow of the American Physical Society. He has nearly 40 years of research experience in materials science and condensed matter physics, mostly on superconductivity, both on applied and basic science aspects. He completed undergraduate studies in Physics at the Univ. of Buenos Aires, Argentina (1983), and received his Ph.D. in Physics at the Instituto Balseiro, Bariloche, Argentina (1989). He was a postdoc at the IBM T. J. Watson Research Center (1989-1992) and spent short periods as visiting scientist at ORNL (1992) and several institutions in Europe (Atominstitut der Österreichischen Univ. Vienna, Austria - K. Onnes Lab, Leiden Univ., Holland - Katholieke Univ. Leuven, Belgium - Institut Ciencia dels Materials, Univ. de Barcelona, Spain, 1993). He returned to Bariloche as professor (1993-2001), and in 1998 he became Head of the Low Temperature Group. In 2002 he joined Los Alamos National Laboratory (LANL) as Physics Team Leader of the Superconductivity Technology Center, whose goal was to develop Coated Conductors (CC), which are wires of High Temperature Superconductors (HTS), through a National Program of the DOE Office of Electricity. In 2020 he became Leader of the MPA-Quantum Group, until he retired in Dec. 2022. Leonardo’s research on critical current density (Jc) and vortex pinning in HTS has significantly contributed to shaping the topic. He has more than 250 publications, >14500 citations and h-index 57 (Google Scholar). Leonardo is now an Affiliate to the University of Connecticut at Storrs, CT, USA, and his main present research interests include the use of CC for fusion reactors and space applications. The purpose of the course will be to introduce the basic concepts and physics of superconductivity to engineering students at the PhD level. The emphasis will be on the applied aspects, with only a brief mention to microscopic theories. The lectures will be focused on the behavior of high temperature superconductors (HTS), and the contrasts to conventional superconductors will be mentioned mostly to point out the relevance of vortex fluctuations.

Summary of the program: Status of the SC technology today. Historical overview to introduce the basic properties: Tc, R=0, persistent currents. Electrodynamics: Meissner effect, thermodynamic implication, difference with a perfect conductor, thermodynamic critical field Hc, free energy. London equations: penetration depth (l), critical fields in thin films, measurement of l(T) (films, spheres), screening currents, depairing current density Jd and its relationship with Hc, demagnetizing effects, intermediate state in type I SC. Order parameter, coherence length. Ginzburg-Landau theory: upper critical fields Hc2 and Hc3, thin films. Domain wall energy, type II superconductors. Vortices: thermodynamics, equilibrium magnetization. Anisotropy, layered HTS, pancake vortices. Vortex pinning: Concept of Jc, pinning energies and forces, transport & magnetization measurements, critical state model, I-V curves. Strong and weak pinning mechanisms, collective pinning, correlated and random disorder. Methods to enhance Jc: pinning landscape engineering by particle irradiation and second phase additions. Processing-properties correlations. Radiation damage at high fluences: implication for fusion reactors magnets. Vortex dynamics: Ginzburg parameter, vortex solid and liquid phases, flux creep, effects on I-V curves, dissipation. AC response and losses.

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Presentazione orale

P.D.1-1 - Febbraio