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Unit VI Superconductivity JIT Nashik Contents Unit VI Superconductivity JIT Nashik Contents 1 Superconductivity 1 1.1 Classification ............................................. 1 1.2 Elementary properties of superconductors ............................... 2 1.2.1 Zero electrical DC resistance ................................. 2 1.2.2 Superconducting phase transition ............................... 3 1.2.3 Meissner effect ........................................ 3 1.2.4 London moment ....................................... 4 1.3 History of superconductivity ...................................... 4 1.3.1 London theory ........................................ 5 1.3.2 Conventional theories (1950s) ................................ 5 1.3.3 Further history ........................................ 5 1.4 High-temperature superconductivity .................................. 6 1.5 Applications .............................................. 6 1.6 Nobel Prizes for superconductivity .................................. 7 1.7 See also ................................................ 7 1.8 References ............................................... 8 1.9 Further reading ............................................ 10 1.10 External links ............................................. 10 2 Meissner effect 11 2.1 Explanation .............................................. 11 2.2 Perfect diamagnetism ......................................... 12 2.3 Consequences ............................................. 12 2.4 Paradigm for the Higgs mechanism .................................. 12 2.5 See also ................................................ 12 2.6 References ............................................... 13 2.7 Further reading ............................................ 13 2.8 External links ............................................. 13 3 Technological applications of superconductivity 14 3.1 Magnetic Resonance Imaging (MRI) and Nuclear Magnetic Resonance (NMR) ........... 14 3.2 Particle accelerators and magnetic fusion devices ........................... 14 3.3 High-temperature superconductivity (HTS) .............................. 14 i ii CONTENTS 3.3.1 HTS-based systems ...................................... 15 3.3.2 Holbrook Superconductor Project .............................. 15 3.3.3 Tres Amigas Project ..................................... 15 3.3.4 Magnesium diboride ..................................... 15 3.4 Notes ................................................. 15 4 SQUID 16 4.1 History and design .......................................... 16 4.1.1 DC SQUID .......................................... 16 4.1.2 RF SQUID .......................................... 17 4.1.3 Materials used ........................................ 17 4.2 Uses .................................................. 18 4.2.1 Proposed uses ......................................... 18 4.3 See also ................................................ 18 4.4 Notes ................................................. 19 4.5 References .............................................. 19 5 Maglev 20 5.1 Development ............................................. 20 5.2 History ................................................ 21 5.2.1 First maglev patent ...................................... 21 5.2.2 New York, United States, 1913 ............................... 21 5.2.3 New York, United States, 1968 ............................... 21 5.2.4 Hamburg, Germany, 1979 .................................. 21 5.2.5 Birmingham, United Kingdom, 1984–95 .......................... 21 5.2.6 Emsland, Germany, 1984–2012 ............................... 22 5.2.7 Japan, 1969–present ..................................... 22 5.2.8 Vancouver, Canada and Hamburg, Germany, 1986–88 ................... 22 5.2.9 Berlin, Germany, 1989–91 .................................. 23 5.2.10 South Korea, 1993–present .................................. 23 5.3 Technology .............................................. 23 5.3.1 Electromagnetic suspension ................................. 24 5.3.2 Electrodynamic suspension (EDS) .............................. 24 5.3.3 Tracks ............................................ 25 5.3.4 Evaluation .......................................... 25 5.3.5 Evacuated tubes ....................................... 26 5.3.6 Energy use .......................................... 26 5.3.7 Comparison with conventional trains ............................. 26 5.3.8 Comparison with aircraft ................................... 27 5.4 Economics .............................................. 27 5.5 Records ................................................ 28 5.5.1 History of maglev speed records ............................... 28 CONTENTS iii 5.6 Systems ................................................ 28 5.6.1 Test tracks .......................................... 28 5.6.2 Operational systems ..................................... 28 5.7 Maglevs under construction ...................................... 29 5.7.1 AMT test track – Powder Springs, Georgia ......................... 30 5.7.2 Beijing S1 line ........................................ 30 5.7.3 Changsha Maglev ....................................... 30 5.7.4 Tokyo – Nagoya – Osaka ................................... 30 5.7.5 SkyTran – Tel Aviv (Israel) ................................. 30 5.8 Proposed maglev systems ....................................... 30 5.8.1 Australia ........................................... 30 5.8.2 Italy .............................................. 31 5.8.3 United Kingdom ....................................... 31 5.8.4 United States ......................................... 31 5.8.5 Puerto Rico .......................................... 32 5.8.6 Germany ........................................... 32 5.8.7 Switzerland .......................................... 32 5.8.8 China ............................................. 32 5.8.9 India ............................................. 33 5.8.10 Malaysia ........................................... 33 5.8.11 Iran .............................................. 33 5.8.12 Taiwan ............................................ 33 5.8.13 Hong Kong .......................................... 33 5.9 Incidents ............................................... 33 5.10 See also ................................................ 34 5.11 Notes ................................................. 34 5.12 References .............................................. 34 5.13 Further reading ............................................ 38 5.14 External links ............................................. 38 6 Nanotechnology 39 6.1 Origins ................................................. 39 6.2 Fundamental concepts ......................................... 40 6.2.1 Larger to smaller: a materials perspective ........................... 41 6.2.2 Simple to complex: a molecular perspective ......................... 41 6.2.3 Molecular nanotechnology: a long-term view ......................... 42 6.3 Current research ............................................ 42 6.3.1 Nanomaterials ......................................... 42 6.3.2 Bottom-up approaches .................................... 43 6.3.3 Top-down approaches ..................................... 44 6.3.4 Functional approaches .................................... 44 6.3.5 Biomimetic approaches .................................... 44 iv CONTENTS 6.3.6 Speculative .......................................... 44 6.3.7 Dimensionality in nanomaterials ............................... 45 6.4 Tools and techniques ......................................... 45 6.5 Applications .............................................. 46 6.6 Implications .............................................. 46 6.6.1 Health and environmental concerns .............................. 47 6.7 Regulation ............................................... 47 6.8 See also ................................................ 48 6.9 References ............................................... 48 6.10 External links ............................................. 51 6.11 Text and image sources, contributors, and licenses .......................... 52 6.11.1 Text .............................................. 52 6.11.2 Images ............................................ 56 6.11.3 Content license ........................................ 58 Chapter 1 Superconductivity A high-temperature superconductor levitating above a magnet A magnet levitating above a high-temperature superconductor, cooled with liquid nitrogen. Persistent electric current flows on the surface of the superconductor, acting to exclude the magnetic idealization of perfect conductivity in classical physics. field of the magnet (Faraday's law of induction). This current effectively forms an electromagnet that repels the magnet. The electrical resistivity of a metallic conductor decreases gradually as temperature is lowered. In ordinary conduc- tors, such as copper or silver, this decrease is limited by impurities and other defects. Even near absolute zero, a real sample of a normal conductor shows some resis- tance. In a superconductor, the resistance drops abruptly to zero when the material is cooled below its critical temperature. An electric current flowing through a loop of superconducting wire can persist indefinitely with no power source.*[1]*[2]*[3]*[4] In 1986, it was discovered that some cuprate-perovskite ceramic materials have a critical temperature above 90 K (−183 °C).*[5] Such a high transition temperature is Video of a Meissner effect in a high temperature superconductor
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