Superconductivity: Basics and Applications to Magnets

Preface to Second Edition
Acknowledgements
Contents
About the Author
1 Introduction
	1.1 Why Low Temperature Is so Exciting?
	1.2 How to Conduct Experiment at Low Temperatures?
	1.3 Gas Liquefaction
		1.3.1 Isenthalpic Process
		1.3.2 Isentropic Process
		1.3.3 The Linde–Hampson Process
		1.3.4 The Claude Process
		1.3.5 Liquefaction of Helium (1908)
		1.3.6 Collins Liquefaction Cycle
	1.4 Discovery of Superconductivity—A Fall-Out of Helium Liquefaction
	References
2 The Phenomenon of Superconductivity and Type II Superconductors
	2.1 Electrical Conduction in Metals
	2.2 The Phenomenon of Superconductivity
	2.3 The Critical Magnetic Field
	2.4 The Meissner Effect (Field Expulsion)
		2.4.1 Perfect Diamagnetism
		2.4.2 The Penetration Depth
		2.4.3 Magnetization in Superconductors
		2.4.4 The Intermediate State
	2.5 Two-Fluid Model
	2.6 Thermodynamics of Superconductors
		2.6.1 The Gibbs Free Energy
		2.6.2 Specific Heat
		2.6.3 Phase Transition
	2.7 Thermal Conductivity
	2.8 Thermoelectric Power
	2.9 The Energy Gap
	2.10 The Isotope Effect
	2.11 Flux Quantization
	2.12 The Concept of Coherence Length and Positive Surface Energy
	2.13 Determination of Energy Gap (Single Particle Tunnelling)
	2.14 The Josephson Effect (Pair Tunnelling)
		2.14.1 DC Josephson Effect
		2.14.2 AC Josephson Effect
		2.14.3 The SQUID
	2.15 Type II Superconductors—Abrikosov’s Concept of Negative Surface Energy
		2.15.1 Lower and Upper Critical Magnetic Field
		2.15.2 The Mixed State
		2.15.3 Current Flow and Mixed State
		2.15.4 Measuring Transport Critical Current
		2.15.5 Magnetization in Type II Superconductors
		2.15.6 Irreversible Magnetization
		2.15.7 The Bean’s Critical-State Model and Magnetization
		2.15.8 The Kim Model
		2.15.9 Flux Creep
		2.15.10 Critical Current by Magnetization Method
	2.16 Surface Superconductivity—Critical Magnetic Field Bc3
	2.17 Paramagnetic Limit
	References
3 High-Temperature Cuprate Superconductors and Later Discoveries
	3.1 Discovery of Superconductivity in La-Ba-Cu-O System (Tc = 35 K)
	3.2 The Y-Ba-Cu-O (YBCO) System—First Superconductor with Tc Above 77 K
		3.2.1 Method of Synthesis of YBCO
		3.2.2 Some Peculiar Properties of YBCO
		3.2.3 YBCO Wires and Tapes
	3.3 The Bi-Sr-Ca-Cu-O (BSCCO) System
		3.3.1 Bi-2223 Wires and Tapes
		3.3.2 First Generation (1G)-BSCCO Current Leads
	3.4 The Tl-Ba-Ca-Cu-O System
	3.5 The Hg-Ba-Ca-Cu-O System
	3.6 Flux Vortices, Critical Current Density and Flux Pinning in High-Tc Superconductors
	3.7 Critical Surface of High-Tc Superconductors
	3.8 The Depairing Current
	3.9 Grain Boundary Problem in High-Tc Superconductors
	3.10 Discovery of Superconductivity in Magnesium Diboride (MgB2)
		3.10.1 Peculiar Properties of MgB2
		3.10.2 Crystal and Electronic Structure and Energy Gaps in MgB2
		3.10.3 The Boron Isotope Effect
		3.10.4 Some Physical Properties of MgB2
		3.10.5 Summery of the Various Properties of MgB2
	3.11 The Discovery of Iron-Based Superconductors—LaFeAsO 1111 Compounds
		3.11.1 High Tc (> 50 K) in Sm and Nd-Based Oxypnictides
		3.11.2 Superconductivity in K-Doped BaFe2As2 122 Compounds
		3.11.3 Superconductivity in Iron-Chalcogenides
	3.12 Superconductivity at 203 K in Sulphur Hydride (H3S)
	3.13 Superconductivity at Room Temperature (Tc = 288 K @ 267 GPa)
	References
4 A Review of Theories of Superconductivity
	4.1 A Chronology of Theories of Superconductivity
	4.2 Londons’ Theory
	4.3 The Ginzburg–Landau Theory
		4.3.1 Flux Exclusion and Zero Electrical Resistance
		4.3.2 Flux Quantization
		4.3.3 GL—Parameter and Type II Superconductors
		4.3.4 Josephson Effect
	4.4 The BCS Theory of Superconductivity
		4.4.1 The Cooper Pairs
		4.4.2 Formulation of the Microscopic Theory
		4.4.3 Transition Temperature
		4.4.4 The Energy Gap
		4.4.5 Critical Field and Specific Heat
	4.5 Anomalous Properties of the Cuprates
		4.5.1 Temperature-Hole Concentration Phase Diagram
		4.5.2 Normal State Resistivity
		4.5.3 Presence of Pseudo-Gap in Highly Underdoped Superconductors
		4.5.4 Comparison with Conventional Metallic Superconductors
	4.6 Possible Theories of HTS
		4.6.1 The Resonating Valence Bond (RVB) Theory
		4.6.2 The Spin Fluctuation Theory
		4.6.3 Revisiting BCS Theory to Explain HTS Superconductors
		4.6.4 Positive Feedback Mechanism for High-Tc Superconductivity
		4.6.5 Pairing in Strongly Correlated Electron Systems
		4.6.6 Three-Band d-p Model
	4.7 Theories of Newly Emerged Superconductors
		4.7.1 Theory of Superconductivity in MgB2
		4.7.2 Theory of Iron-Based Superconductors (IBSC)
		4.7.3 Superconductivity in Sulphur Hydride (H3S)
	References
5 Conventional Practical Superconductors
	5.1 Superconductors Useful for Magnet Application
	5.2 Thermal and Electromagnetic Instability Problem—The Multifilamentary Superconductors
		5.2.1 Degradation and Flux Jump
		5.2.2 The Adiabatic or Intrinsic Stability
		5.2.3 The Dynamic and Cryostatic Stability
		5.2.4 Multifilamentary Superconducting Wires
		5.2.5 Twisting and Transposition of the Multifilamentary Wires
	5.3 Losses in Practical Superconductors
		5.3.1 Hysteresis Losses
		5.3.2 Losses Due to Filament Coupling
		5.3.3 Proximity Coupling Losses
		5.3.4 Losses Due to Eddy Currents
		5.3.5 Losses Due to Self-field Effect
		5.3.6 Losses Due to Transport Current
		5.3.7 AC Losses in High Temperature Oxide Superconductors
	5.4 AC Loss Measurement Methods
		5.4.1 Electric Method
		5.4.2 Magnetization Method
		5.4.3 Calorimetric Method
	5.5 Practical Superconductors—The Ubiquitous Nb-Ti Superconductor
		5.5.1 Emergence of Nb-Ti as a Superconductor for Magnets
		5.5.2 The Phase Diagram of Nb-Ti
		5.5.3 Optimization of Jc in Nb-Ti Wires
		5.5.4 Developments in the Fabrication Process of MF Cu/Nb-Ti Composite Conductors
		5.5.5 Use of Diffusion Barrier and Filament Spacing
		5.5.6 Nb-Ti Cable-in-Conduit Conductors (CICC)
	5.6 The Discovery of A-15 Nb3Sn Superconductor
		5.6.1 Emergence of Nb3Sn as High-Field Superconductor
		5.6.2 The Bronze Process
		5.6.3 Parameters to Be Optimized
		5.6.4 Elemental Additions to Nb3Sn
		5.6.5 The Internal Tin (IT) Process
		5.6.6 The Jelly Roll Process
		5.6.7 The Rod Restacking Process (RRP)
		5.6.8 The Powder-in-Tube (PIT) Process
		5.6.9 Conductor for High-Luminosity LHC Quadrupole Magnets
		5.6.10 The In Situ Process
	5.7 The A-15 Nb3Al MF Superconductor
		5.7.1 Phase Diagram of Nb-Al System
		5.7.2 Mass Production of JR Nb3Al Conductors by JAERI for ITER
		5.7.3 The Rapid Heating, Quench and Transformation (RHQT) Technique
	5.8 The V3Ga Tapes and Multifilamentary Wires
		5.8.1 The V-Ga Binary Phase Diagram
		5.8.2 V3Ga Diffusion Tapes
		5.8.3 Bronze-Processed V3Ga MF Conductors
		5.8.4 V3Ga Conductor by PIT Method
	References
6 Practical Cuprate Superconductors
	6.1 Introduction
	6.2 2G REBCO Tape Wires (Coated Conductors)
		6.2.1 Enhancement of Jc Through Heavy Doping
		6.2.2 Development of Flexible Fine Round REBCO Wires with High Mechanical Strength
		6.2.3 Next Generation High-Current REBCO STAR Wire for Compact Magnets
		6.2.4 High Engineering Current Density (Je) in REBCO Wires
		6.2.5 REBCO Deposition on 30 µm Hastelloy Substrate and High Je
		6.2.6 High-Current CORC Cables
		6.2.7 REBCO–CORC Cable-In-Conduit Conductors (CORC-CICC)
		6.2.8 The Roebel Bar Cable
		6.2.9 HTS CroCo Cable Development for DEMO Fusion Reactor
		6.2.10 Supremacy of REBCO-Coated Conductors
	6.3 The Promising Bi2Sr2CaCu2Ox (Bi-2212) Practical Wires and Cables
		6.3.1 Development of a 10 kA Bi-2212 Conductor
		6.3.2 Bubble Formation in PIT Bi-2212 Wire Filaments and Current Blockage
		6.3.3 High Jc in Round Bi-2212 Wires Through Over-Pressure Heat Treatment
		6.3.4 Isotropic Round OP Bi-2212 Wires Generate a Field of 33.6 T
		6.3.5 AC Loss in Bi-2212 Cable-In-Conduit Conductors
		6.3.6 PIT-OPHT Bi-2212 Rutherford Cable
	6.4 The Bi-2223 Conductors
		6.4.1 The Controlled Over-Pressure (CT-OP) Processed Bi-2223 Superconductors
		6.4.2 Suitability of DI-Bi-2223 for High-Field Magnets
		6.4.3 Low AC Loss Bi-2223 Conductors
		6.4.4 A Comparison Between B-2212 and Bi-2223 Wires
	References
7 Practical Magnesium Diboride (MgB2) Superconductor
	7.1 Introduction
	7.2 Preparation of Bulk MgB2, Single Crystal and Thin Film
	7.3 MgB2 Wires, Tapes and Cables
		7.3.1 Different Variants of PIT Technique—The In Situ PIT Technique
		7.3.2 The Ex Situ PIT Technique
		7.3.3 The Internal Magnesium Diffusion (IMD) Technique
		7.3.4 Enhancement of Jc Through Optimization of Process Parameters and Doping
		7.3.5 A Hybrid IMD/PIT Technique
	7.4 Low AC Loss MgB2 Wires/Cables
	7.5 Rutherford MgB2 Cables
		7.5.1 Rutherford Cable with Al-Al2O3 Metal-Matrix Composite (MMC) Sheath
	7.6 Thin Film Route for MgB2 Conductors
	7.7 An Upswing in the Use of MgB2 for Applications
	References
8 Iron-Based Practical Superconductors
	8.1 General Features of Iron-Based Superconductors
	8.2 Structure and Phase Diagrams of IBSC Compounds
	8.3 Electronic and Structural Phase Diagram of LnOFeAs, 1111 Compounds
	8.4 Superconductivity in LaFeCoAsO Induced by Co Doping
		8.4.1 Superconductivity in Co-Doped Sm(FeCo)AsO Compounds
	8.5 Phase Diagram and Characteristic Properties of (Li/Na)FeAs 111 Compounds
		8.5.1 Superconductivity in Co-Doped AFeAs 111 Compounds
	8.6 Phase Diagram and Characteristic Properties of 122 BaFe2As2 Compound
		8.6.1 Superconductivity in K-Doped BaFe2As2 Compound
	8.7 Phase Diagram of Iron Chalcogenides 11 Compounds
		8.7.1 Behaviour of the Mixed Phase, Fe1+xTe1−xSex
	8.8 Pressure Effect in Iron-Based Superconductors
		8.8.1 Pressure Effects in 1111 Compounds
		8.8.2 Pressure Effects in 111 Compounds
		8.8.3 Pressure Effects in 122 Compounds
		8.8.4 Pressure Effects in 11 FeSex Compounds
	8.9 Critical Current in IBSC Wires and Tapes
		8.9.1 Fabrication of Wires/Tapes Through PIT Technique
		8.9.2 Achieving High Jc in IBSC 122 Wires/Tapes
		8.9.3 Multifilamentary IBSC Wires/Tapes for Applications
		8.9.4 The Thin Film Route
	References
9 Building Laboratory Superconducting Magnets and Present Status of High-Field Magnets
	9.1 Introduction
	9.2 Evolution of Superconducting Magnets
	9.3 Unique Features of a Superconducting Magnet
	9.4 Design Considerations of a Solenoid Magnet
		9.4.1 Specific Example of a 7 T Superconducting (Nb–Ti) Magnet
		9.4.2 Optimization of Vapour-Cooled Current Leads
		9.4.3 Magnet Quench
		9.4.4 The Minimum Propagating Zone
		9.4.5 Quench Voltage and Temperature Rise
		9.4.6 Quench Protection
		9.4.7 The Persistent Switch
		9.4.8 Training of the Magnet
	9.5 High Homogeneity Field
		9.5.1 High Homogeneity Field by Compensated Coils
	9.6 An 11 T Nb–Ti/Nb3Sn Combination Magnet
		9.6.1 Winding the Background Nb–Ti Magnet
		9.6.2 Winding the Nb3Sn Magnet
		9.6.3 Preparation of Current Terminals
		9.6.4 Heat Treatment and Impregnation
		9.6.5 Assembly of Magnet Coils and Operation
	9.7 Intense Field Magnets
		9.7.1 A 21.1 T Superconducting Magnet Built by NIMS
		9.7.2 A 24 T Magnet Using GdBCO Insert Coil (NIMS)
		9.7.3 A 26.8 T YBCO Insert Coil at NHMFL (FSU)
		9.7.4 A Record Field of 32 T at NHMFL (FSU)
		9.7.5 A New World Record of Magnetic Field—45.5 T at NHMFL (FSU)
		9.7.6 First High Current (4 kA) Insert Magnet Wound with CORC® Cable
	9.8 Cryo-Free Superconducting Magnets (CFSM)
		9.8.1 Important Considerations for CFSM System Design
		9.8.2 The Design and Winding of the Magnet
		9.8.3 The Current Lead Design
		9.8.4 The Cryostat Design
		9.8.5 Operating the Magnet
	References
10 Superconducting Magnets in Accelerators
	10.1 The Accelerators
	10.2 Role of Superconducting Magnets in Accelerators
	10.3 High-Energy Accelerators Using Superconducting Magnets
		10.3.1 Tevatron (FNAL, USA)
		10.3.2 Hadron Electron Ring Accelerator (HERA), DESY, Hemberg, Germany
		10.3.3 Superconducting Super Collider (SSC), Texas, USA (Abandoned)
		10.3.4 Relativistic Heavy Ion Collider (RHIC), BNL, Upton, USA
		10.3.5 Large Hadron Collider (LHC), CERN (Switzerland/France)
	10.4 Unique Features of the Accelerator Magnets with Special Reference to LHC
		10.4.1 The Coil Geometry
		10.4.2 The Collars
		10.4.3 The Yoke
		10.4.4 The Magnets
		10.4.5 Training of Magnets
		10.4.6 The Quench Protection
	10.5 High-Field Magnets for Future Accelerators
		10.5.1 The Nb3Sn Conductor for Accelerator Magnets
		10.5.2 Nb3Sn Accelerator Magnets Development at FNAL
		10.5.3 EuCARD Nb3Sn Dipole Magnets
	10.6 Common Coil High-Field Dipole Magnets—A New Approach (LBNL)
	10.7 The 15 T HD-2 Dipole
	10.8 Work on the Design of 15 T Nb3Al Dipole
	10.9 Linear Colliders with Special Reference to ILC
		10.9.1 Superconducting Magnets in ILC
		10.9.2 The ILC Quadrupole and Dipole Correctors
		10.9.3 The Wiggler Magnets
		10.9.4 The Undulator
		10.9.5 Other Superconducting Magnets
	10.10 Superconducting Magnets in Cyclotron
		10.10.1 Cyclotron Magnet
		10.10.2 Some Landmark Superconducting Cyclotrons
		10.10.3 K-500 Cyclotron at NSCL (Michigan State University)
		10.10.4 K-500 Cyclotron (VECC, Kolkata)
		10.10.5 K-1200 Cyclotron (NSCL, MSU)
		10.10.6 K-2500, RIKEN Superconducting Ring Cyclotron
	10.11 New Developments in Accelerator and Magnet Technology
		10.11.1 The High-Luminosity–Large Hadron Collider (HL-LHC)
		10.11.2 Factors Influencing the Specific Parameters of Dipole and Quadrupole Magnets
		10.11.3 Testing of Nb3Sn Quadrupole and Dipole Magnets for High HL-LHC
	10.12 Future Circular Collider (FCC)
		10.12.1 Magnet Technology for FCC-Hh
	10.13 The High-Energy 28 TEV Large Hadron Collider (HE-LHC)
		10.13.1 Emergence of Supercable-In-Conduit Conductors (SuperCICC) for High-Field Accelerator Magnets
		10.13.2 The HE-LHC Dipoles in Hybrid formation—A New Concept
	10.14 The State-of-the-Art Electron–Ion Collider (EIC)—A Discovery Machine
		10.14.1 ERHIC—The Electron–Ion Collider at Brookhaven National Laboratory
		10.14.2 The Jefferson Lab Electron–Ion Collider (JLEIC)
		10.14.3 Magnets in the Interaction Region (IR) of the JLEIC
		10.14.4 Modular Quadrupole Design for EIC
		10.14.5 Passive Superconducting Shield for Magnets in EIC
	References
11 Superconducting Magnets in Fusion Reactors
	11.1 The Fusion Reaction
	11.2 Plasma Ignition
	11.3 Plasma Confinement
		11.3.1 The Inertial Confinement
		11.3.2 The Magnetic Confinement
		11.3.3 Magnetic Mirror
		11.3.4 The Stellarator
		11.3.5 The Tokamak
		11.3.6 Magnetic Field in a Tokamak
	11.4 Important Superconducting Tokamaks
		11.4.1 Tokamak Development in USSR/Russia
		11.4.2 The Russian Hybrid Fusion–Fission Reactor
		11.4.3 TFTR (Tokamak Fusion Test Reactor, Non-superconducting), PPPL, USA
		11.4.4 JET (Joint European Torus), Non-superconducting (Culham, UK)
		11.4.5 Mega Ampere Spherical Tokamak (MAST) Upgrade
		11.4.6 Tore Supra (NRC, Cadarache, France)
		11.4.7 WEST (Tungsten (W) Environment in Steady-State Tokamak)
		11.4.8 JT-60 SA (Japan Torus-60 Super Advance), JAERI, Naka, Japan
		11.4.9 KSTAR (Korean Superconducting Tokamak Reactor), NFRI, Daejeon
		11.4.10 K-DEMO Being Built by Korea and PPPL
		11.4.11 EAST (Experimental Advance Superconducting Tokamak, IPP, China)
		11.4.12 HL-2M Tokamak—A New Tokamak Built by China
		11.4.13 CFETR (China Fusion Engineering Testing Reactor)—A Power-Producing Tokamak
		11.4.14 SST-1 (Steady-State Superconducting Tokamak-1), IPR, India
		11.4.15 SST-2 (Steady-State Tokamak-2) Fusion Reactor, IPR, India
	11.5 The International Thermonuclear Experimental Reactor (ITER)
		11.5.1 The ITER Design
		11.5.2 The TF Coil Winding Pack
		11.5.3 The PF Coil Winding Pack
		11.5.4 The CS Coils
		11.5.5 Final Assembly of ITER
		11.5.6 HTS Hybrid Current Leads for ITER
	11.6 The Stellarator, W7-X (Wendelstein 7-X) Greifswald, Germany
		11.6.1 The Magnet System of W7-X
		11.6.2 Bus Bars and HTS Hybrid Current Leads
		11.6.3 Performance Tests on Wendelstein 7-X
		11.6.4 Wendelstein 7-X Upgrade to Divertor Stage
	11.7 IGNITOR (Italian–Russian Collaboration), ITP, TRINITI, Russia
	References
12 Other Applications of Superconducting Magnets
	12.1 Introduction
	12.2 Nuclear Magnetic Resonance (NMR)
		12.2.1 Salient Features of an NMR Magnet and the Present Status
		12.2.2 The Magnet and Shim Coil Design
		12.2.3 Jointing of the Wires
		12.2.4 Bruker’s ‘UltraStabilized™’ Cryostat for 2 K Operation
		12.2.5 Another World Record in NMR Magnet in 2015
		12.2.6 A New World Record of 1.2 GHz NMR Magnet System by Bruker BioSpin (2020)
		12.2.7 JEOL’s ‘Zero Boil-Off Magnet for NMR System’
		12.2.8 A Split NMR Magnet System
		12.2.9 Superconducting Magnet (30.5 T) for a 1.3 GHz NMR Spectrometer
	12.3 Magnets in Magnetic Resonance Imaging (MRI)
		12.3.1 The Elements of an MRI Scanner
		12.3.2 Evolution of MRI Magnet design—A Brief Description
		12.3.3 Compensated Solenoid Magnet Design
		12.3.4 Multicoil Magnet Design
		12.3.5 Design of Cryogen-Free MgB2 Magnets for MRI
		12.3.6 A Mini Conduction-Cooled 1.5 T MgB2 Finger MRI Magnet at MIT
		12.3.7 Solid-Cryogen Cooling of NMR and MRI Magnets
		12.3.8 Some Recent Developments in MRI Scanners
	12.4 Superconducting High-Gradient Magnetic Separator (SHGMS)—Principle of Magnetic Separation
		12.4.1 SHGMS Magnet Design
		12.4.2 Recent Developments of SHGMS
		12.4.3 Superconducting Pulsating High-Gradient Magnetic Separator (SP-HGMS)
	12.5 Superconducting Magnet Energy Storage (SMES)
		12.5.1 Magnet Design in SMES
		12.5.2 Factors Affecting SMES
		12.5.3 Some Examples of SMES
		12.5.4 High-Tc Superconductor (HTS) SMES
	12.6 Maglev and Rotating Machines
		12.6.1 Magnetic Levitation (Maglev)
		12.6.2 Motors and Generators
	References
Index