Superconductor Levitation: Concepts and Experiments

251 Pages·2019·17.343 MB·English

by  Chan-Joong Kim

Chan-Joong Kim
Superconductor
Levitation
Concepts and Experiments
Superconductor Levitation
Chan-Joong Kim
Superconductor Levitation
Concepts and Experiments
Chan-Joong Kim
Neutron Utilization Research Division
Korea Atomic Energy Research Institute
Daejeon, Korea (Republic of)
Illustrations by Jinwon Kim
Industrial and Management Engineering
Pohang University of Science and Technology
Pohang, Korea (Republic of)
ISBN 978-981-13-6767-0 ISBN 978-981-13-6768-7 (eBook)
https://doi.org/10.1007/978-981-13-6768-7
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Preface
Superconductors have two unique properties: the first is zero resistance, and the
second is perfect diamagnetism. This perfect diamagnetism was discovered by the
German physicist Meissner, and is called “Meissner effect.” Since superconductors
repel the magnetic field of a magnet, they levitate above it. Following the discovery
of high-temperature (T) superconductors in 1986 by Bednorz and Müller, Meissner
c
effect can now be observed in general scientific laboratories.
I have been studying the manufacturing process and properties of high-T super-
c
conducting materials for over 30 years. Over the course of long-term studies, I
planned and conducted many exciting experiments on superconductivity with stu-
dents. I also collected useful photographs of the Meissner effect and the magnetic
flux pinning of superconductors. I have explored the phenomenon of superconduc-
tivity through various superconducting experiments, and have included the useful
knowledge in this book.
Chapter 1 introduces the history of superconducting phenomena, which formed
the topic of a Nobel Prize in Physics. The discoveries of superconducting phenom-
ena, BCS theory, Josephson tunnelling, Type 2 superconductors and the high-T
c
superconductors are briefly summarized. It also describes the basic knowledge of
superconductivity needed for superconductivity experiments, including zero resis-
tance, persistent current, the Meissner effect, and superconductors of Types 1 and 2.
Chapter 2 introduces the method of synthesis of the high-T oxide superconduc-
c
tors used in superconductivity experiments. Descriptions are given of the solid-
phase synthesis method in which raw powders are mixed and heated to form a
superconducting phase, and the melt growth processes that produce large-grained
superconductors with high magnetic levitation forces.
Chapters 3 and 4 present the method of the measurement of the magnetic levita-
tion force and the magnetic field trapped in the superconductors. The magnetization
process of superconductors using the mixed state of a Type 2 superconductor is
described.
Chapter 5 introduces the Meissner effect experiment, in which a superconductor
levitates above a magnet. Chapter 6 presents an easy way to measure the magnetic
levitation force of a superconductor using a kitchen or electronic scale.
vii
viii Preface
Chapter 7 introduces various superconducting levitation experiments. These
experiments exploit both the perfect diamagnetism and trapped magnetic field in the
(superconducting + normal) mixed state of Type 2 superconductors. A description is
given of the field-cooling method that traps the magnetic force of the magnet in
superconductors and a method for adjusting the position and height of the magnet
levitating above a superconductor. Techniques for levitating multiple magnets, toy
cars, a fishbowl, and human being above superconductors are also described.
Chapters 8 and 9 introduce superconducting suspension experiments using the
flux pinning of superconductors. This phenomenon is known as the suspension
effect or the fishing effect. Descriptions are given of the levitation of a superconduc-
tor above a single magnet, the simultaneous levitation of a superconductor and a
magnet, the suspension of superconductors next to a magnet, a suspension experi-
ment using a glass or measuring cup and a method for manufacturing a suspension
experiment kit.
Chapter 10 explains how to make superconducting magnetic levitation (Maglev)
trains. A description is given of the method of the elliptical magnetic rail, used for
the demonstration of the Maglev train. A description is also given of how to con-
struct the Maglev train with superconductors, how to cool the superconductors to
keep the train moving on the rails, and how to adjust the levitation height of the
train.
Finally, Chap. 11 summarizes the applications of superconductors, including a
flywheel energy storage device with high energy storage efficiency, magnetic sepa-
ration using bulk superconductors, frictionless bearings, current leads and super-
conductors for magnetic shielding, superconducting wires, and superconducting
propulsion ships.
I am very pleased to have published a book on superconducting demonstration
methods. This book is based on research conducted at the superconductivity labora-
tory of the Korea Atomic Energy Research Institute (KAERI). This book contains
more than 400 original photos taken in the laboratory. I believe this is the first book
to systematically summarize superconducting magnetic levitation and suspension
experiments. I aimed to make it easy for the public to follow the superconductivity
experiments, and I hope this book will provide useful information about supercon-
ductivity experiments to high school students, college students, science teachers and
professors.
I would like to thank the students and collaborators who have conducted super-
conductivity research in the KAERI laboratory with me. I would also like to express
my gratitude to my beloved wife Sunyoung, my daughter Sunkyoung and my son
Sunho, who encouraged my research activities in daily life. Finally, I would like to
share the proceeds of this book with missionaries working for God’s kingdom.
Daejeon, Korea (Republic of) Chan-Joong Kim
February, 2019
Contents
1 History of Superconductivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Nobel Prizes in Superconductivity Research . . . . . . . . . . . . . . . . . . 1
1.2 Zero Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 Persistent Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.4 Influence of Magnetic Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.5 Meissner Effect: Perfect Diamagnetism . . . . . . . . . . . . . . . . . . . . . 4
1.6 Type 1 Superconductors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.7 T ype 2 Superconductors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.8 B CS Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.9 H igh-T Superconductors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
c
1.10 High-T and Low-T . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
c c
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2 S ynthesis of High-T Oxide Superconductors . . . . . . . . . . . . . . . . . . . 13
c
2.1 I ntroduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.2 S olid State Reaction Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.2.1 Materials Needed for Synthesis . . . . . . . . . . . . . . . . . . . . . . 13
2.2.2 Synthesis of Oxide Superconductors . . . . . . . . . . . . . . . . . . 14
2.3 Melt Growth Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.3.1 Solid-State Sintering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.3.2 Melt Growth (MG) Process . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.3.3 Seeded Melt Growth (SMG) Process . . . . . . . . . . . . . . . . . . 26
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
3 Magnetic Levitation Forces of Superconductors . . . . . . . . . . . . . . . . . 33
3.1 Magnetic Levitation Force . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
3.2 Measurement of Magnetic Levitation Forces . . . . . . . . . . . . . . . . . 33
3.2.1 Measuring Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
3.2.2 Measurement Procedure. . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
3.3 Force–Distance (F–d) Curves of Superconductors . . . . . . . . . . . . . 35
3.3.1 ZFC Superconductor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.3.2 FC Superconductor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
ix
x Contents
3.4 Effects of Grain Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3.5 Magnetic Field Trapped in Superconductors . . . . . . . . . . . . . . . . . . 40
3.5.1 Measurement of Trapped Magnetic Fields . . . . . . . . . . . . . 40
3.5.2 Magnetic Field Contour Map . . . . . . . . . . . . . . . . . . . . . . . . 41
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
4 Cooling Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.1 Phase Diagram of Superconductors . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.1.1 Type 1 Superconductor . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.1.2 Type 2 Superconductor . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.2 Cooling Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
4.2.1 Zero Field Cooling (ZFC): Meissner Effect . . . . . . . . . . . . 45
4.2.2 Field Cooling (FC): Meissner Effect Plus Flux Pinning . . . 47
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
5 Levitation Experiments Using the Meissner Effect . . . . . . . . . . . . . . . 51
5.1 Array of Magnets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
5.1.1 Meissner Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
5.1.2 Ball on a Fountain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
5.1.3 Magnetic Platform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
5.1.4 Levitation of Superconductors above Magnets . . . . . . . . . . 54
5.2 Levitation Experiments Using Ring-Shaped Magnets . . . . . . . . . . . 55
5.2.1 Ring-Shaped Magnets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
5.2.2 Levitation of Superconductors . . . . . . . . . . . . . . . . . . . . . . . 55
5.2.3 Size of Superconductors . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
5.3 Platforms for Magnetic Levitation . . . . . . . . . . . . . . . . . . . . . . . . . . 57
5.3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
5.3.2 Ring-Shaped Magnetic Platform . . . . . . . . . . . . . . . . . . . . . 59
5.3.3 Board-Like Platforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
5.3.4 Cooling Using LN. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
2
5.3.5 Levitation above Ring-Shaped Platforms . . . . . . . . . . . . . . 63
5.3.6 Levitation above Board-Type Platforms . . . . . . . . . . . . . . . 65
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
6 M easurement of Magnetic Levitation Forces Using Scales . . . . . . . . . 67
6.1 K itchen Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
6.1.1 Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
6.1.2 Materials Needed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
6.1.3 Experimental Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
6.2 Digital Electronic Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
6.2.1 Materials Needed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
6.2.2 Experimental Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
6.2.3 Distance Control Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
6.2.4 LN Pot and Thermal Insulation . . . . . . . . . . . . . . . . . . . . . 74
2
6.2.5 Measurement of Repulsive Magnetic Forces . . . . . . . . . . . . 74
Contents xi
7 Levitation of Magnets above Superconductors . . . . . . . . . . . . . . . . . . 77
7.1 Flux Pinning in Type 2 Superconductors . . . . . . . . . . . . . . . . . . . . . 77
7.1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
7.1.2 Preparation of Materials and Experimental Procedure . . . . 78
7.1.3 Magnetic Field of Magnets . . . . . . . . . . . . . . . . . . . . . . . . . 79
7.1.4 Confirmation of Trapped Magnetic Fields . . . . . . . . . . . . . . 80
7.2 Adjustment of Levitation Height: Horizontal . . . . . . . . . . . . . . . . . 81
7.2.1 Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
7.2.2 Plastic LN Pots for Cooling Superconductors . . . . . . . . . . 82
2
7.2.3 Preparation of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
7.2.4 Experimental Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
7.2.5 Facing Area Between Magnet and Superconductor . . . . . . . 85
7.3 Adjustment of Levitation Height: Vertical . . . . . . . . . . . . . . . . . . . . 86
7.3.1 Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
7.3.2 Preparation of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
7.3.3 Experimental Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
7.3.4 Levitation of Disc-Shaped Magnets . . . . . . . . . . . . . . . . . . . 89
7.3.5 Levitation of Ring-Shaped Magnets . . . . . . . . . . . . . . . . . . 90
7.4 Position Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
7.4.1 Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
7.4.2 Preparation of Materials (See Fig. 7.15) . . . . . . . . . . . . . . . 91
7.4.3 Experimental Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
7.4.4 Understanding of Trapped Magnetic Fields . . . . . . . . . . . . . 93
7.4.5 Summary of Position Control Experiments . . . . . . . . . . . . . 93
7.5 Rectangular Magnets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
7.6 Coupled Magnets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
7.6.1 Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
7.6.2 Preparation of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
7.6.3 Experimental Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
7.6.4 Levitation of Coupled Magnets . . . . . . . . . . . . . . . . . . . . . . 99
7.6.5 Rotation of Magnets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
7.7 Levitation of Bead-Shaped Magnets . . . . . . . . . . . . . . . . . . . . . . . . 100
7.7.1 Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
7.7.2 Preparation of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
7.7.3 Experimental Procedure: FC . . . . . . . . . . . . . . . . . . . . . . . . 102
7.7.4 Experimental Procedure: ZFC . . . . . . . . . . . . . . . . . . . . . . . 102
7.7.5 Precautions for Handling LN . . . . . . . . . . . . . . . . . . . . . . . 104
2
7.7.6 Levitation of Multiple Bead-Shaped Magnets . . . . . . . . . . . 105
7.8 Glass Angels on Coupled Magnets . . . . . . . . . . . . . . . . . . . . . . . . . 105
7.8.1 Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
7.8.2 Preparation of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
7.8.3 Experimental Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
7.8.4 Levitation of a Magnetic Platform . . . . . . . . . . . . . . . . . . . . 108