High Temperature Superconductors: Progress and Issues

by Prof. Jan Evetts (UNIVERSITY OF CAMBRIDGE, Department of Materials Science and Metallurgy, UK)

Wednesday 26 Jun 2002, 11:00 → 12:00 Europe/Zurich

593--11 (CERN)

The development of High Temperature Superconductors, seen from a materials scientist's point of view, is relevant to the superconductivity community at CERN: their possible high current applications can include high performance magnets for future accelerators. There is an urgent need to develop a quantitative description of HTS conductors in terms of their complex anisotropy, inhomogeneity and dimensionality. This is essential both for the practical specification of a conductor and for charting routes to conductor optimisation. The critical current, the n-value, dissipation and quenching characteristics are amongst most important parameters that make up an engineering specification. A brief introduction will first be given of the turbulent early years of research that followed the discovery of HTS by Bednorz and Müller in 1986. Progress in the development of practical conductors will be summarised, and the vital role of grain boundaries and grain texture described. Then the important problem of current percolation in granular structures and current injection at contacts and shunts will be addressed. There are three components to the percolation problem, (i) the characteristics and properties of individual grains and grain boundaries, (ii) the microstructure, texture and grain morphology, and (iii) the macroscopic geometrical constraints such as conductor size and shape, and the direction of the magnetic field and its history. Progress in characterising and modelling current and flux percolation for different conductor types will be surveyed and particular gaps in understanding and areas of neglect discussed.

Organiser(s): Davide Vitè / HR Division Robert Herzog / LHC Division

Note: Academic Contact: prof. Jan Evetts, IRC in Superconductivity, Department of Materials Science and Metallurgy University of Cambridge, Pembroke Street, Cambridge CB2 3QZ, UK Web: http://www.msm.cam.ac.uk/dmg/ Email: jee2@cam.ac.uk Free seminar, no registration

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