Applications of Superconductivity

Transcription

1 Applications of Superconductivity

2 NATO ASI Series Advanced Science Institute Series A Series presenting the results of activities sponsored by the NATO Science Committee, which aims at the dissemination of advanced scientific and technological knowledge, with a view to strengthening links between scientific communities. The Series is published by an international board of publishers in conjunction with the NATO Scientific Affairs Division A. Life Sciences B. Physics C. Mathematical and Physical Sciences D. Behavioural and Social Sciences E. Applied Sciences F. Computer and Systems Sciences G. Ecological Sciences H. Cell Biology I. Global Environment Change Plenum Publishing Corporation London and New York Kluwer Academic Publishers Dordrecht, Boston and London Springer-Verlag Berlin, Heidelberg, New York, London, Paris and Tokyo PARTNERSHIP SUB-SERIES 1. Disarmament Technologies 2. Environment 3. High Technology 4. Science and Technology Policy 5. Computer Networking Kluwer Academic Publishers Springer-Verlag / Kluwer Academic Publishers Kluwer Academic Publishers Kluwer Academic Publishers Kluwer Academic Publishers The Partnerschip Sub-Series incorporates activities undertaken in collaboration with NATO's Cooperation Partners, the countries of the CIS and Central and Eastern Europe, in Priority Areas of concern to those countries. NATO-PCO-DATA BASE The electronic index to the NATO ASI Series provides full bibliographical references (with keywords and/or abstracts) to about 50,000 contributions from international scientists published in all sections of the NATO ASI Series. Access to the NATO-PCO-DATA-BASE is possible via a CD-ROM "NATO Science and Technology Disk" with user-friendly retrieval software in English, French, and German ( WTV GmbH and DATAWARE Technologies, Inc. 1989). The CD-ROM contains the AGARD Aerospace Database. The CD-ROM can be ordered through any member of the Board of Publishers or through NATO-PCO, Overijse, Belgium. Series E: Applied Sciences - Vol. 365

3 Applications of Superconductivity edited by Harold Weinstock Air Force Office of Scientific Research, Arlington, VA, U.S.A.... " Springer-Science+Business Media, B.V.

4 Proceedings of the NATO Advanced Study Institute on Applications of Superconductivity Loen, Norway 8-20 June, 1997 A C.I. P. Catalogue record for this book is available from the Library of Congress. ISBN ISBN (ebook) DOI / Printed on acid-free paper AII Rights Reserved 2000Springer Science+Business Media Dordrecht Originally published by Kluwer Academic Publishers in 2000 Softcover reprint of the hardcover 1st edition 2000 No part of the material protected by this copyright notice may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording or by any information storage and retrieval system, without written permission from the copyright owner.

5 to Linda, Steve and Allen

6 TABLE OF CONTENTS PREFACE ACKNOWLEDGMENTS ix xi 1. LOW- AND HIGH-Tc SQUIDs AND SOME APPLICATIONS J. Clarke 2. MULTICHANNEL SQUID BIOMAGNETIC SYSTEMS 61 J. Vrba 3. APPLICATIONS OF SQUID MAGNETOMETERS TO 139 BIOMAGNETISM AND NONDESTRUCTIVE EVALUATION J. P. Wikswo 4. APPLICATIONS OF JOSEPHSON ELECTRONICS 229 IN DIGITAL SYSTEMS J. X. Przybysz, Sr. 5. SUPERCONDUcrOR DEVICES 247 FOR ULTRAFAST COMPUTING K. K. Likharev 6. MICROWAVE APPLICATIONS OF 295 HIGH TEMPERATURE SUPERCONDUCTORS H. J. Chaloupka 7. MRlMAGNETS 385 F. J. Davies 8. POWER QUALITY, 415 MICRO SUPERCONDUCTING MAGNETIC ENERGY STORAGE SYSTEMS, AND FAULT CURRENT LIMITERS M. Parizh and E. Leung

7 viii 9. HIGH CURRENT APPLICATION OF SUPERCONDUCTIVITY Part I: Applications in Research and Industrial Areas P. Komarek HIGH CURRENT APPLICATION OF SUPERCONDUCTIVITY Part II: Superconducting Magnets for Fusion P. Komarek THE MECHANICAL DEFORMATION PROCESSING OF HIGH-TEMPERATURE SUPERCONDUCTING COMPOSITE TAPE T. Freltoft and Z. Han APPLICATIONS OF HIGH TEMPERATURE SUPERCONDUCTORS IN MAGNETIC BEARINGS AND FLYWHEELS K.B.Ma CRYOGENIC SYSTEMS FOR SUPERCONDUCTING DEVICES H. 1. M. ter Brake SUPERCONDUCTOR MEASUREMENT TECHNIQUES AND CRYOSTAT DESIGN J. Ekin SUPERCONDUCTIVITY R&D AT ISTEC AND ELSEWHERE IN JAPAN G. Pindoria

8 PREFACE This book, in essence the proceedings of a NATO Advanced Study Institute with the same title, is designed to provide in-depth coverage of many, but not all, of the major current applications of superconductivity, and of many that still are being developed. It will be of value to scientists and engineers who have interests in the research and production aspects of the technology, as well as in the applications themselves. The ftrst three chapters (by Clarke, Vrba and Wikswo) are devoted to an understanding of the principles, fabrication and uses of SQUID magnetometers and gradiometers, with the greatest emphasis on biomagnetism and nondestructive evaluation (NDE). For the most part, traditional low-temperature superconductor (LTS) SQUIDs are used, but particularly for NDE, high-temperature superconductor (HTS) SQUIDs are proving useful and often more convenient. The succeeding three chapters (by Przybysz, Likharev and Chaloupka) cover broader aspects of superconducting electronics. The ftrst two of these deal primarily with digital L TS circuits, while the third discusses in great detail passive component applications using HTS materials. Currently, HTS ftlters are undergoing intense J3-site testing at cellular telephone base stations. While it is clear that HTS ftlters outperform conventional ftlters in reducing signal loss and allowing for more channels in a given bandwidth, it isn't yet certain that the cellular telephone industry sees sufficient economic beneftts to make a ftrm decision to use HTS ftlters universally in its systems. If this application is generally adapted, the market for these ftlters should be quite large. Chapter 7 (by Davies) is the frrst of four successive chapters (one by Parizh and Leong, and the remaining two by Komarek) on magnet applications, generally of rather large scale. Mostly these involve L TS magnets, with MRI and particle accelerator magnets being the largest source of revenue for the superconductor industry. Nevertheless, the introduction of HTS magnets into the power industry for load leveling, uninterruptible power modules (UPMs) and fault current limiters (FCLs) appears quite promising. It is unfortunate, however, that a chapter has not been included on other power industry applications, primarily transformers and power transmission lines. Superconducting transformers are more efficient than conventional ones, they occupy far less volume and are more environmentally friendly; namely noxious oils are replaced by liquid nitrogen. While superconductive transmission lines appear more costly at this time than traditional copper lines, there are instances in heavily-populated areas in which the ability of a superconductor to carry a higher current in a confmed region may make it an attractive choice. Chapter 11 (by Freltoft and Han) elucidates the process by which HTS tapes of BSCCO material embedded in silver is made. This type of processing, known as the powder-in-tube (PIT) or oxygen-powder-in-tube (OPIT) method, is about the only technique knowp at present that has produced long lengths of HTS tape useful for transmission lines and the winding of magnets. While the present cost per kilo-ampmeter of BSCCO tape is about 100 times the cost of conventional copper or LTS transmission lines, many prototype magnets and motors have been built using the PIT method. On the horizon are a number of fabrication techniques under development to make long lengths of HTS tape using YBCO as the HTS material of choice. YBCO is more desirable generally because it can maintain relatively high critical-current density ix

9 x in the presence of a magnetic field. While very high critical-current densities have been obtained for short sections of YBCO tape - typically values of about 10 6 A/cm 2 at 77 K and ambient magnetic field for lengths of a few centimeters - the longest lengths yet produced with uniform high critical-current values are only on the order of one meter. This is clearly a work in progress. Chapter 12 (by Ma) is the last chapter that deals specifically with applications per se, addressing itself to the use ofhts material for magnetic bearings in low-loss flywheels. Such flywheels can be used both as energy storage devices and for attitude control in a space vehicle. The remaining three chapters are somewhat eclectic, but nevertheless valuable. Chapter 13 (by ter Brake) provides a very comprehensive summary of the cryogenic systems needed to support superconducting systems, with much of the underlying physics included. Chapter 14 (by Ekin) has been included as an aid to all experimentalists in the field of superconductivity. It details how to design cryogenic measuring systems properly and how to take valid measurements. The fmal chapter (by Pindoria) is an exposition of the superconductivity research program in Japan, with special emphasis on the activities at the largest research center there, ISTEC, which is a joint venture of the Japanese government (through MITI) and a consortium of industrial contributors, a limited number of whom are from outside Japan. In summary, this volume should serve as a resource to its readers for in-depth scientific coverage of a vast number of superconductor-based applications. Some of these applications are quite mature, e.g., LTS magnets for MRI, while many others are in various stages of maturity. Undoubtedly, some will emerge as major "winners;" others will continue to hold only niche markets or fade from the scene. It is not easy to make good predictions in general because so much depends not only on success in fabricating LTS or HTS devices, but also on competition from other new or improving technologies. I do wish at this pomt to make one bold prediction about something mentioned only briefly in the chapter on SQUID applications in biomagnetism. Namely, I predict there will be major market for SQUID arrays to detect the onset or presence of ischemic heart disease via magnetic-field mapping, without the need for a stress test or the introduction of any radiation or substance to the human body. Initial clinical tests, mainly in Germany, are encouraging, and wider-scale clinical testing now is just beginning there and elsewhere. If the market for these SQUID-array systems reaches into the tens of thousands of units, the cost of mechanical refrigeration to support these systems will plummet, thus making all of superconductor-based electronics more attractive economically. Arlington, VA August 1999 Harold Weinstock

10 ACKNOWLEDGMENTS This book comprises the official proceedings of the NATO Advanced Study Institute (ASI) held 8-20 June 1997 at the Hotel Alexandra in Loen, Norway. The Institute would not have been possible without generous fmancial (and other nonmonetary forms of) support from the Scientific and Environmental Affairs Division of NATO. Hence, I first must thank NATO for making the Institute and these proceedings possible. Its sequential support of five ASls which I have proposed and directed in the field of superconductivity since 1988 is greatly appreciated. Substantial additional fmancial support has been provided by my employer, the Air Force Office of Scientific Research (AFOSR), through its European Office of Aerospace Research and Development. Furthermore, I must thank AFOSR for allowing me to work on activities related to the ASI during the course of my normal duties and for providing other institutional resources. It is a pleasure, as well, to acknowledge additional financial support from the Naval Research Laboratory and the National Science Foundation, this latter organization having provided travel support to US researchers. Neither the ASI nor these proceedings would have been possible without the dedicated and superior efforts of Mrs. Sandra Ronayne, a Management Assistant at AFOSR. She handled with aplomb all of the administrative tasks required before, during and after the ASI, and was of valuable assistance in the editing process itself. The incredible natural surroundings and ambience of the Hotel Alexandria were inspiring and provided the appropriate intellectual climate to motivate the contributors to these proceedings. The staff and management of the hotel were most responsive, and the conference facilities were as good or better than any I've seen elsewhere. I am especially indebted to Mr. Erik Brendefur for attending to all our special needs. I reserve my greatest thanks to the thirteen distinguished scientists who were ASI lecturers and who (in some cases together with their collaborators) subsequently became the authors of the chapters in these proceedings. During the ASI all devoted from one to two weeks of their valuable time to lectures, workshops and informal discussions with about 80 young researchers from over 15 countries. Perhaps their most difficult task was to prepare a manuscript for these proceedings and to deal with this rather fussy editor. For all of these reasons, I am very much in their debt. Thanks are due also to the aforementioned ASI participants who provided the enthusiasm for superconductivity that helped fuel the efforts of the lecturers. As in the past, I fmally must thank my family, especially my wife Linda, for excusing the many distractions caused by the ASI and the editing of these proceedings. Arlington, VA August 1999 Harold Weinstock Xl