Critical Currents In A 15 Superconductors

Applications of superconductivity at the boiling temperature of liquid nitrogen continue to challenge physicists, materials scientists and engineers all over the world eight years after the discovery of high temperature superconductivity. The key to a solution of today's problems lies in the optimization of the defect structure in well-oriented oxide materials as well as in a fundamental understanding of the magnetic microstructures in the mixed state and how they are affected by the crystallographic nature ('dimensionality') of these materials. Fifteen invited overview lectures as well as approximately 150 contributed papers highlight the state of the art in this important field of superconductivity and review our current knowledge of critical currents in superconductors.

Compound superconductors with the Al5 structure carry the promise of the second generation in practical superconductivity. They will provide higher operating magnetic fields at higher tem peratures than the preceding alloy superconductors. To fulfill this promise, their brittle nature must be accommodated in a fila mentary structure. Achieving this has been no simple task and imaginative research and clever production techniques have led to many usable conductor configurations. In addition, several new and exciting possibilities are being proposed; for example, in situ processing promises easier production with improved strain toler ance. It is timely, therefore, to take measure of what we have achieved and to assess our understanding so that we may choose, with some confidence, paths for future research and potential ap plications. To meet these needs, the International Cryogenic Materials Conference Board has sponsored this special topic conference on Filamentary Al5 Superconductors bringing together superconductiv ity researchers, superconducting wire producers, and high field magnet users to discuss current research problems. That the in formation exchange was intensive and successful is evidenced by the excellent papers in this volume. In order to capture some of the synergistic wisdom generated in discussions at the conference several people were asked to assemble and interpret the comments and concerns of the fusion, high energy physics, solid state phys ics, and metallurgy groups.

This proceedings volume reviews the recent developments of superconducting materials for practical applications and critical current characteristics. It contains 18 invited papers and 72 contributed papers. The scope of these papers includes: (1) synthesis and processing of practical materials, (2) properties of high-Tc tapes, coils and bulk materials, (3) critical currents and microstructure, (4) flux dynamics and pinning mechanisms, (5) applications of high-Tc materials, (6) applications of low-Tc superconductors, (7) processing, physical properties and applications of high-Tc thin films.

The Third International Cryogenic Materials Conference (ICMC) was held in Madison, Wisconsin, in conjunction with the Cryogenic Engineering Conference (CEC) in August 1979. The University of Wisconsin hosted the two conferences in an excellent manner and deserves special recognition and praise. The synergism produced by conducting the two conferences simultaneously continues to be strong. Materials remain a demanding challenge and, in some cases, an obstacle to effective application of cryogenic technology. The association of materials specialists and cryogenic engineers every other year centers their attention on the most needed areas of research. The present ICMC Board met during the conference and elected two new members, E. W. Collings (U. S.) and D. Evans (England). The board voted to conduct two smaller, special-topic conferences in 1980. These are Filamentary A15 Superconductors, which was held at Brookhaven National Laboratories, Upton, New York in May 1980, and Fundamentals of Nonmetallics and Composites at Low Temperatures, held in Geneva, Switzerland in August 1980. The 1981 CEC/ICMC will be held August 10 through 14 in San Diego, California.

This volume will focus on the theory and experiments leading to quantitative understanding of the magnetic field and temperature dependence of critical current densities in high-temperature superconductors. Topics will include: critical currents and flux-pinning, flux flow and flux creep, anisotropy of critical fields and currents, properties of the flux lattice and the irreversibility line, magnetization, granularity. Contents:Critical Currents in Neutron Irradiated High Temperature Superconductors (H W Weber)Radiation Induced Disorder as a Unique Method for Studing Electronic States of HTSC's and Modifying Their Properties (B N Goshchitskii et al)Influence of Fast Neutron Irradiation on Various Types of HTSC Materials: Comprehensive Study (H Szymczak et al)Critical Currents and Angular Dependence in Magnetic a.c. Response: Test for Intrinsic Pinning (L Krusin-Elbaum et al)Why the Critical Current Densities of High Tc's Vary Anomalously with Temperature, Field and Time (S Senoussi et al)The Effect of the Intragranular Irreversible Magnetization on the Intergranular and Intragranular Critical Currents (S L Ginzburg et al)Bean-Livingstone Surface barrier in High Temperature Superconductors (M Konczykowski)Pinning Centers in C-Axis Oriented Bi-Sr-Ca-Cu-O Thin Films (G Jung et al)The Effect of an Electric Current on Microwave Absorption in a YBaCuO Ceramic Superconductor (J Stankowski et al)and other papers Readership: Condensed matter physicists, electronic and electrical engineers and chemists. keywords:

Superconductors is neither about basic aspects of superconductivity nor about its applications, but its mainstay is superconducting materials. Unusual and unconventional features of a large variety of novel superconductors are presented and their technological potential as practical superconductors assessed. The book begins with an introduction to basic aspects of superconductivity. The presentation is readily accessible to readers from a diverse range of scientific and technical disciplines, such as metallurgy, materials science, materials engineering, electronic and device engineering, and chemistry. The derivation of mathematical formulas and equations has been kept to a minimum and, wherever necessary, short appendices with essential mathematics have been added at the end of the text. The book is not meant to serve as an encyclopaedia, describing each and every superconductor that exists, but focuses on important milestones in their exciting development.