Unit VI Superconductivity JIT Nashik Contents

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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 conductors, 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 resistance. 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 theoretically impossible for a conventional superconduc- (black pellet) with a NdFeB magnet (metallic) tor, leading the materials to be termed high-temperature superconductors. Liquid nitrogen boils at 77 K, and su- Superconductivity is a phenomenon of exactly zero perconduction at higher temperatures than this facilitates electrical resistance and expulsion of magnetic fields oc- many experiments and applications that are less practical curring in certain materials when cooled below a charac- at lower temperatures. teristic critical temperature. It was discovered by Dutch physicist Heike Kamerlingh Onnes on April 8, 1911 in Leiden. Like ferromagnetism and atomic spectral lines, 1.1 Classification superconductivity is a quantum mechanical phenomenon. It is characterized by the Meissner effect, the complete ejection of magnetic field lines from the interior of the Main article: Superconductor classification superconductor as it transitions into the superconducting state. The occurrence of the Meissner effect indicates There are many criteria by which superconductors are that superconductivity cannot be understood simply as the classified. The most common are:

1 2 CHAPTER 1. SUPERCONDUCTIVITY

• Response to a magnetic field: A superconductor can be Type I, meaning it has a single critical field, above which all superconductivity is lost; or Type II, meaning it has two critical fields, between which it allows partial penetration of the magnetic field.

• By theory of operation: It is conventional if it can be explained by the BCS theory or its derivatives, or unconventional, otherwise.

• By critical temperature: A superconductor is generally considered high temperature if it reaches a superconducting state when cooled using liquid nitrogen – that is, at only Tc > 77 K) – or low temperature if more aggressive cooling techniques are required Electric cables for accelerators at CERN. Both the massive and to reach its critical temperature. slim cables are rated for 12,500 A. Top: conventional cables for LEP; bottom: superconductor-based cables for the LHC • By material: Superconductor material classes include chemical elements (e.g. mercury or lead), alloys (such as niobium-titanium, germanium- niobium, and niobium nitride), ceramics (YBCO MRI machines. Experiments have demonstrated that cur- and magnesium diboride), or organic superconduc- rents in superconducting coils can persist for years with- tors (fullerenes and carbon nanotubes; though per- out any measurable degradation. Experimental evidence haps these examples should be included among the points to a current lifetime of at least 100,000 years. The- chemical elements, as they are composed entirely of oretical estimates for the lifetime of a persistent current carbon). can exceed the estimated lifetime of the universe, depending on the wire geometry and the temperature.*[3] In a normal conductor, an electric current may be visu- 1.2 Elementary properties of su- alized as a fluid of electrons moving across a heavy ionic lattice. The electrons are constantly colliding with the perconductors ions in the lattice, and during each collision some of the energy carried by the current is absorbed by the lattice Most of the physical properties of superconductors vary and converted into heat, which is essentially the vibra- from material to material, such as the heat capacity and tional kinetic energy of the lattice ions. As a result, the the critical temperature, critical field, and critical current energy carried by the current is constantly being dissi- density at which superconductivity is destroyed. pated. This is the phenomenon of electrical resistance and Joule heating. On the other hand, there is a class of properties that are independent of the underlying material. For instance, all The situation is different in a superconductor. In a con- superconductors have exactly zero resistivity to low ap- ventional superconductor, the electronic fluid cannot be plied currents when there is no magnetic field present or resolved into individual electrons. Instead, it consists of if the applied field does not exceed a critical value. The bound pairs of electrons known as Cooper pairs. This existence of these“universal”properties implies that su- pairing is caused by an attractive force between electrons perconductivity is a thermodynamic phase, and thus pos- from the exchange of phonons. Due to quantum mechan- sesses certain distinguishing properties which are largely ics, the energy spectrum of this Cooper pair fluid pos- independent of microscopic details. sesses an energy gap, meaning there is a minimum amount of energy ΔE that must be supplied in order to excite the fluid. Therefore, if ΔE is larger than the thermal en- 1.2.1 Zero electrical DC resistance ergy of the lattice, given by kT, where k is Boltzmann's constant and T is the temperature, the fluid will not be The simplest method to measure the electrical resistance scattered by the lattice. The Cooper pair fluid is thus a of a sample of some material is to place it in an electrical superfluid, meaning it can flow without energy dissipa- circuit in series with a current source I and measure the tion. resulting voltage V across the sample. The resistance of In a class of superconductors known as type II supercon- the sample is given by Ohm's law as R = V / I. If the ductors, including all known high-temperature supercon- voltage is zero, this means that the resistance is zero. ductors, an extremely small amount of resistivity appears Superconductors are also able to maintain a current with at temperatures not too far below the nominal supercon- no applied voltage whatsoever, a property exploited in ducting transition when an electric current is applied in superconducting electromagnets such as those found in conjunction with a strong magnetic field, which may be 1.2. ELEMENTARY PROPERTIES OF SUPERCONDUCTORS 3 caused by the electric current. This is due to the motion perature, superconducting materials cease to supercon- of magnetic vortices in the electronic superfluid, which duct when an external magnetic field is applied which is dissipates some of the energy carried by the current. If greater than the critical magnetic field. This is because the the current is sufficiently small, the vortices are station- Gibbs free energy of the superconducting phase increases ary, and the resistivity vanishes. The resistance due to this quadratically with the magnetic field while the free energy effect is tiny compared with that of non-superconducting of the normal phase is roughly independent of the mag- materials, but must be taken into account in sensitive ex- netic field. If the material superconducts in the absence periments. However, as the temperature decreases far of a field, then the superconducting phase free energy is enough below the nominal superconducting transition, lower than that of the normal phase and so for some fi- these vortices can become frozen into a disordered but nite value of the magnetic field (proportional to the square stationary phase known as a “vortex glass”. Below this root of the difference of the free energies at zero magnetic vortex glass transition temperature, the resistance of the field) the two free energies will be equal and a phase tran- material becomes truly zero. sition to the normal phase will occur. More generally, a higher temperature and a stronger magnetic field lead to a smaller fraction of the electrons in the superconducting 1.2.2 Superconducting phase transition band and consequently a longer London penetration depth of external magnetic fields and currents. The penetration depth becomes infinite at the phase transition. The onset of superconductivity is accompanied by abrupt changes in various physical properties, which is the hall- mark of a phase transition. For example, the electronic heat capacity is proportional to the temperature in the normal (non-superconducting) regime. At the superconducting transition, it suffers a discontinuous jump and thereafter ceases to be linear. At low temperatures, it varies instead as e*−α/T for some constant, α. This expo- nential behavior is one of the pieces of evidence for the existence of the energy gap. The order of the superconducting phase transition was long a matter of debate. Experiments indicate that the transition is second-order, meaning there is no latent heat. Behavior of heat capacity (cv, blue) and resistivity (ρ, green) at the superconducting phase transition However, in the presence of an external magnetic field there is latent heat, because the superconducting phase In superconducting materials, the characteristics of su- has a lower entropy below the critical temperature than perconductivity appear when the temperature T is low- the normal phase. It has been experimentally demonstrated*[9] that, as a consequence, when the magnetic ered below a critical temperature Tc. The value of this critical temperature varies from material to mate- field is increased beyond the critical field, the resulting rial. Conventional superconductors usually have critical phase transition leads to a decrease in the temperature of temperatures ranging from around 20 K to less than 1 the superconducting material. K. Solid mercury, for example, has a critical tempera- Calculations in the 1970s suggested that it may actually ture of 4.2 K. As of 2009, the highest critical tempera- be weakly first-order due to the effect of long-range fluc- ture found for a conventional superconductor is 39 K for tuations in the electromagnetic field. In the 1980s it was * * magnesium diboride (MgB2), [6] [7] although this ma- shown theoretically with the help of a disorder field the- terial displays enough exotic properties that there is some ory, in which the vortex lines of the superconductor play doubt about classifying it as a “conventional”super- a major role, that the transition is of second order within conductor.*[8] Cuprate superconductors can have much the type II regime and of first order (i.e., latent heat) higher critical temperatures: YBa2Cu3O7, one of the first within the type I regime, and that the two regions are sep- cuprate superconductors to be discovered, has a critical arated by a tricritical point.*[10] The results were strongly temperature of 92 K, and mercury-based cuprates have supported by Monte Carlo computer simulations.*[11] been found with critical temperatures in excess of 130 K. The explanation for these high critical temperatures remains unknown. Electron pairing due to phonon ex- 1.2.3 Meissner effect changes explains superconductivity in conventional superconductors, but it does not explain superconductivity Main article: Meissner effect in the newer superconductors that have a very high critical temperature. When a superconductor is placed in a weak external Similarly, at a fixed temperature below the critical tem- magnetic field H, and cooled below its transition tem- 4 CHAPTER 1. SUPERCONDUCTIVITY

perature, the magnetic field is ejected. The Meissner ef- The mixed state is actually caused by vortices in the elec- fect does not cause the field to be completely ejected but tronic superfluid, sometimes called fluxons because the instead the field penetrates the superconductor but only flux carried by these vortices is quantized. Most pure to a very small distance, characterized by a parameter elemental superconductors, except niobium and carbon λ, called the London penetration depth, decaying expo- nanotubes, are Type I, while almost all impure and com- nentially to zero within the bulk of the material. The pound superconductors are Type II. Meissner effect is a defining characteristic of superconductivity. For most superconductors, the London penetration depth is on the order of 100 nm. 1.2.4 London moment

The Meissner effect is sometimes confused with the kind Conversely, a spinning superconductor generates a mag- of diamagnetism one would expect in a perfect electri- netic field, precisely aligned with the spin axis. The ef- cal conductor: according to Lenz's law, when a changing fect, the London moment, was put to good use in Gravity magnetic field is applied to a conductor, it will induce an Probe B. This experiment measured the magnetic fields of electric current in the conductor that creates an opposing four superconducting gyroscopes to determine their spin magnetic field. In a perfect conductor, an arbitrarily large axes. This was critical to the experiment since it is one of current can be induced, and the resulting magnetic field the few ways to accurately determine the spin axis of an exactly cancels the applied field. otherwise featureless sphere. The Meissner effect is distinct from this̶it is the spontaneous expulsion which occurs during transition to superconductivity. Suppose we have a material in its normal 1.3 History of superconductivity state, containing a constant internal magnetic field. When the material is cooled below the critical temperature, we would observe the abrupt expulsion of the internal magnetic field, which we would not expect based on Lenz's law. The Meissner effect was given a phenomenological explanation by the brothers Fritz and Heinz London, who showed that the electromagnetic free energy in a superconductor is minimized provided

∇2H = λ−2H where H is the magnetic field and λ is the London penetration depth. This equation, which is known as the London equa- Heike Kamerlingh Onnes (right), the discoverer of superconduc- tion, predicts that the magnetic field in a superconductor tivity. Paul Ehrenfest, Hendrik Lorentz, Niels Bohr stand to his decays exponentially from whatever value it possesses at left. the surface. Main article: History of superconductivity A superconductor with little or no magnetic field within it is said to be in the Meissner state. The Meissner state breaks down when the applied magnetic field is too large. Superconductivity was discovered on April 8, 1911 by Superconductors can be divided into two classes accord- Heike Kamerlingh Onnes, who was studying the resis- ing to how this breakdown occurs. In Type I supercon- tance of solid mercury at cryogenic temperatures using ductors, superconductivity is abruptly destroyed when the the recently produced liquid helium as a refrigerant. At the temperature of 4.2 K, he observed that the resistance strength of the applied field rises above a critical value Hc. * Depending on the geometry of the sample, one may ob- abruptly disappeared. [14] In the same experiment, he tain an intermediate state*[12] consisting of a baroque also observed the superfluid transition of helium at 2.2 K, pattern*[13] of regions of normal material carrying a without recognizing its significance. The precise date and circumstances of the discovery were only reconstructed magnetic field mixed with regions of superconducting * material containing no field. In Type II superconductors, a century later, when Onnes's notebook was found. [15] In subsequent decades, superconductivity was observed raising the applied field past a critical value Hc1 leads to a mixed state (also known as the vortex state) in which an in several other materials. In 1913, lead was found to su- increasing amount of magnetic flux penetrates the mate- perconduct at 7 K, and in 1941 niobium nitride was found rial, but there remains no resistance to the flow of electric to superconduct at 16 K. current as long as the current is not too large. At a second Great efforts have been devoted to finding out how and critical field strength Hc2, superconductivity is destroyed. why superconductivity works; the important step oc- 1.3. HISTORY OF SUPERCONDUCTIVITY 5

curred in 1933, when Meissner and Ochsenfeld dis- This important discovery pointed to the electron-phonon covered that superconductors expelled applied magnetic interaction as the microscopic mechanism responsible for fields, a phenomenon which has come to be known as the superconductivity. * Meissner effect. [16] In 1935, Fritz and Heinz London The complete microscopic theory of superconductivity showed that the Meissner effect was a consequence of the was finally proposed in 1957 by Bardeen, Cooper and minimization of the electromagnetic free energy carried * * Schrieffer. [21] This BCS theory explained the supercon- by superconducting current. [17] ducting current as a superfluid of Cooper pairs, pairs of electrons interacting through the exchange of phonons. 1.3.1 London theory For this work, the authors were awarded the Nobel Prize in 1972. The first phenomenological theory of superconductivity The BCS theory was set on a firmer footing in 1958, was London theory. It was put forward by the brothers when N. N. Bogolyubov showed that the BCS wavefunc- Fritz and Heinz London in 1935, shortly after the discov- tion, which had originally been derived from a variational ery that magnetic fields are expelled from superconduc- argument, could be obtained using a canonical trans- tors. A major triumph of the equations of this theory is formation of the electronic Hamiltonian.*[25] In 1959, their ability to explain the Meissner effect,*[18] wherein Lev Gor'kov showed that the BCS theory reduced to the a material exponentially expels all internal magnetic fields Ginzburg-Landau theory close to the critical tempera- as it crosses the superconducting threshold. By using the ture.*[26]*[27] London equation, one can obtain the dependence of the Generalizations of BCS theory for conventional super- magnetic field inside the superconductor on the distance conductors form the basis for understanding of the phe- to the surface.*[19] nomenon of superfluidity, because they fall into the There are two London equations: lambda transition universality class. The extent to which such generalizations can be applied to unconventional superconductors is still controversial. ∂j n e2 n e2 s = s E, ∇ × j = − s B. ∂t m s m 1.3.3 Further history The first equation follows from Newton's second law for superconducting electrons. The first practical application of superconductivity was developed in 1954 with Dudley Allen Buck's invention of the cryotron.*[28] Two superconductors with greatly 1.3.2 Conventional theories (1950s) different values of critical magnetic field are combined to produce a fast, simple, switch for computer elements. During the 1950s, theoretical condensed matter physicists arrived at a solid understanding of “conventional” Soon after discovering superconductivity in 1911, superconductivity, through a pair of remarkable and Kamerlingh Onnes attempted to make an electromag- important theories: the phenomenological Ginzburg- net with superconducting windings but found that rel- Landau theory (1950) and the microscopic BCS theory atively low magnetic fields destroyed superconductivity (1957).*[20]*[21] in the materials he investigated. Much later, in 1955, G.B. Yntema *[29] succeeded in constructing a small In 1950, the phenomenological Ginzburg-Landau the- 0.7-tesla iron-core electromagnet with superconducting ory of superconductivity was devised by Landau and * niobium wire windings. Then, in 1961, J.E. Kunzler, Ginzburg. [22] This theory, which combined Lan- E. Buehler, F.S.L. Hsu, and J.H. Wernick *[30] made dau's theory of second-order phase transitions with a the startling discovery that, at 4.2 kelvin, a compound Schrödinger-like wave equation, had great success in ex- consisting of three parts niobium and one part tin, was plaining the macroscopic properties of superconductors. capable of supporting a current density of more than In particular, Abrikosov showed that Ginzburg-Landau 100,000 amperes per square centimeter in a magnetic theory predicts the division of superconductors into the field of 8.8 tesla. Despite being brittle and difficult to two categories now referred to as Type I and Type II. fabricate, niobium-tin has since proved extremely useful Abrikosov and Ginzburg were awarded the 2003 Nobel in supermagnets generating magnetic fields as high as 20 Prize for their work (Landau had received the 1962 No- tesla. In 1962 T.G. Berlincourt and R.R. Hake *[31]*[32] bel Prize for other work, and died in 1968). The four- discovered that alloys of niobium and titanium are suit- dimensional extension of the Ginzburg-Landau theory, able for applications up to 10 tesla. Promptly thereafter, the Coleman-Weinberg model, is important in quantum commercial production of niobium-titanium supermag- field theory and cosmology. net wire commenced at Westinghouse Electric Corpora- Also in 1950, Maxwell and Reynolds et al. found that tion and at Wah Chang Corporation. Although niobium- the critical temperature of a superconductor depends on titanium boasts less-impressive superconducting proper- the isotopic mass of the constituent element.*[23]*[24] ties than those of niobium-tin, niobium-titanium has, nev- 6 CHAPTER 1. SUPERCONDUCTIVITY

ertheless, become the most widely used “workhorse” This temperature jump is particularly significant, since it supermagnet material, in large measure a consequence allows liquid nitrogen as a refrigerant, replacing liquid he- of its very-high ductility and ease of fabrication. How- lium.*[35] This can be important commercially because ever, both niobium-tin and niobium-titanium find wide liquid nitrogen can be produced relatively cheaply, even application in MRI medical imagers, bending and focus- on-site. Also, the higher temperatures help avoid some ing magnets for enormous high-energy-particle accelera- of the problems that arise at liquid helium temperatures, tors, and a host of other applications. Conectus, a Eu- such as the formation of plugs of frozen air that can block ropean superconductivity consortium, estimated that in cryogenic lines and cause unanticipated and potentially 2014, global economic activity for which superconduc- hazardous pressure buildup.*[36]*[37] tivity was indispensable amounted to about five billion Many other cuprate superconductors have since been dis- euros, with MRI systems accounting for about 80% of covered, and the theory of superconductivity in these ma- that total. terials is one of the major outstanding challenges of the- In 1962, Josephson made the important theoretical pre- oretical condensed matter physics.*[38] There are cur- diction that a supercurrent can flow between two pieces rently two main hypotheses – the resonating-valence- of superconductor separated by a thin layer of insula- bond theory, and spin fluctuation which has the most sup- tor.*[33] This phenomenon, now called the Josephson port in the research community.*[39] The second hypoth- effect, is exploited by superconducting devices such as esis proposed that electron pairing in high-temperature SQUIDs. It is used in the most accurate available mea- superconductors is mediated by short-range spin waves * * surements of the magnetic flux quantum Φ0 = h/(2e), known as paramagnons. [40] [41] where h is the Planck constant. Coupled with the Since about 1993, the highest temperature superconduc- quantum Hall resistivity, this leads to a precise measure- tor was a ceramic material consisting of mercury, barium, ment of the Planck constant. Josephson was awarded the calcium, copper and oxygen (HgBa2Ca2Cu3O8+δ) with Nobel Prize for this work in 1973. * * Tc = 133–138 K. [42] [43] The latter experiment (138 In 2008, it was proposed that the same mecha- K) still awaits experimental confirmation, however. nism that produces superconductivity could produce a In February 2008, an iron-based family of high- superinsulator state in some materials, with almost infi- * * * temperature superconductors was discovered. [44] [45] nite electrical resistance. [34] Hideo Hosono, of the Tokyo Institute of Technology, and colleagues found lanthanum oxygen fluorine iron arsenide (LaO1-xFₓFeAs), an oxypnictide that superconducts be- 1.4 High-temperature supercon- low 26 K. Replacing the lanthanum in LaO1−xFxFeAs with samarium leads to superconductors that work at 55 ductivity K.*[46] In May 2014, hydrogen sulfide (H 2S) was predicted to be a high-temperature superconductor with a transition temperate of 80 at 160 gigapascals.*[47] In 2015, H 2S has been observed to exhibit superconductivity at below 203 K but at extremely high pressures ̶around 150 gigapascals.*[48]

1.5 Applications

Main article: Technological applications of superconduc- Timeline of superconducting materials tivity Superconducting magnets are some of the most powerful Main article: High-temperature superconductivity electromagnets known. They are used in MRI/NMR machines, mass spectrometers, and the beam-steering mag- Until 1986, physicists had believed that BCS theory for- nets used in particle accelerators. They can also be used bade superconductivity at temperatures above about 30 for magnetic separation, where weakly magnetic particles K. In that year, Bednorz and Müller discovered supercon- are extracted from a background of less or non-magnetic ductivity in a lanthanum-based cuprate perovskite mate- particles, as in the pigment industries. rial, which had a transition temperature of 35 K (Nobel In the 1950s and 1960s, superconductors were used Prize in Physics, 1987).*[5] It was soon found that re- to build experimental digital computers using cryotron placing the lanthanum with yttrium (i.e., making YBCO) switches. More recently, superconductors have been used raised the critical temperature to 92 K.*[35] to make digital circuits based on rapid single ﬂux quan- 1.6. NOBEL PRIZES FOR SUPERCONDUCTIVITY 7

1.6 Nobel Prizes for superconductivity

• Heike Kamerlingh Onnes (1913),“for his investiga- tions on the properties of matter at low temperatures which led, inter alia, to the production of liquid helium” • John Bardeen, Leon N. Cooper, and J. Robert Schri- effer (1972), “for their jointly developed theory of superconductivity, usually called the BCS-theory” • Leo Esaki, Ivar Giaever, and Brian D. Josephson Video of superconducting levitation of YBCO (1973),“for their experimental discoveries regarding tunneling phenomena in semiconductors and superconductors, respectively,”and “for his theoretical predictions of the properties of a supercurrent tum technology and RF and microwave filters for mobile through a tunnel barrier, in particular those phenom- phone base stations. ena which are generally known as the Josephson effects” Superconductors are used to build Josephson junctions which are the building blocks of SQUIDs (supercon- • Georg Bednorz and K. Alex Müller (1987), “for ducting quantum interference devices), the most sensitive their important break-through in the discovery of su- magnetometers known. SQUIDs are used in scanning perconductivity in ceramic materials” SQUID microscopes and magnetoencephalography. Se- • ries of Josephson devices are used to realize the SI Alexei A. Abrikosov, Vitaly L. Ginzburg, and “ volt. Depending on the particular mode of opera- Anthony J. Leggett (2003), for pioneering con- tion, a superconductor-insulator-superconductor Joseph- tributions to the theory of superconductors and su- ”* son junction can be used as a photon detector or as perfluids [52] a mixer. The large resistance change at the transition from the normal- to the superconducting state is used to build thermometers in cryogenic micro-calorimeter pho- 1.7 See also ton detectors. The same effect is used in ultrasensitive bolometers made from superconducting materials. • Andreev reflection Other early markets are arising where the relative effi- • Charge transfer complex ciency, size and weight advantages of devices based on high-temperature superconductivity outweigh the addi- • Color superconductivity in quarks tional costs involved. For example, in wind turbines the • Composite Reaction Texturing lower weight and volume of superconducting generators could lead to savings in construction and tower costs, off- • Conventional superconductor setting the higher costs for the generator and lowering the total LCOE.*[49] • Covalent superconductors Promising future applications include high-performance • Flux pumping smart grid, electric power transmission, transformers, power storage devices, electric motors (e.g. for vehicle • High-temperature superconductivity propulsion, as in vactrains or maglev trains), magnetic • Homes's law levitation devices, fault current limiters, enhancing spin- tronic devices with superconducting materials,*[50] and • Iron-based superconductor superconducting magnetic refrigeration. However, super- • conductivity is sensitive to moving magnetic fields so ap- Kondo effect plications that use alternating current (e.g. transformers) • List of superconductors will be more difficult to develop than those that rely upon direct current. Compared to traditional power lines su- • Little-Parks effect perconducting transmission lines are more efficient and • require only a fraction of the space, which would not only Magnetic levitation lead to a better environmental performance but could also • Macroscopic quantum phenomena improve public acceptance for expansion of the electric grid.*[51] • Magnetic sail 8 CHAPTER 1. SUPERCONDUCTIVITY

• National Superconducting Cyclotron Laboratory [6] Jun Nagamatsu; Norimasa Nakagawa; Takahiro Mu- ranaka; Yuji Zenitani; et al. (2001). “Supercon- • Oxypnictide ductivity at 39 K in magnesium diboride”. Nature 410 (6824): 63–4. Bibcode:2001Natur.410...63N. • Persistent current doi:10.1038/35065039. PMID 11242039.

• Proximity eﬀect [7] Paul Preuss (14 August 2002). “A most unusual superconductor and how it works: ﬁrst-principles calculation • Room-temperature superconductor explains the strange behavior of magnesium diboride”. Research News (Lawrence Berkeley National Laboratory). • Rutherford cable Retrieved 2009-10-28.

• Spallation Neutron Source [8] Hamish Johnston (17 February 2009). “Type-1.5 superconductor shows its stripes”. Physics World (Institute of • Superconducting RF Physics). Retrieved 2009-10-28. • Superconductor classification [9] R. L. Dolecek (1954). “Adiabatic Magnetiza- tion of a Superconducting Sphere”. Physical Re- • Superfluid film view 96 (1): 25–28. Bibcode:1954PhRv...96...25D. doi:10.1103/PhysRev.96.25. • Superfluidity [10] H. Kleinert (1982). “Disorder Version of the Abelian • Superstripes Higgs Model and the Order of the Superconductive Phase Transition” (PDF). Lettere al Nuovo Cimento 35 (13): • Technological applications of superconductivity 405–412. doi:10.1007/BF02754760.

• Superconducting wire [11] J. Hove; S. Mo; A. Sudbo (2002). “Vortex in- teractions and thermally induced crossover from • Timeline of low-temperature technology type-I to type-II superconductivity” (PDF). Physical Review B 66 (6): 064524. arXiv:cond- • Type-I superconductor mat/0202215. Bibcode:2002PhRvB..66f4524H. doi:10.1103/PhysRevB.66.064524. • Type-II superconductor [12] Lev D. Landau; Evgeny M. Lifschitz (1984). Electro- • Unconventional superconductor dynamics of Continuous Media. Course of Theoretical Physics 8. Oxford: Butterworth-Heinemann. ISBN 0- • BCS theory 7506-2634-8. • Bean's critical state model [13] David J. E. Callaway (1990). “On the remarkable structure of the superconducting intermediate state”. Nuclear Physics B 344 (3): 627–645. Bibcode:1990NuPhB.344..627C. doi:10.1016/0550- 1.8 References 3213(90)90672-Z.

[14] H. K. Onnes (1911). “The resistance of pure mercury [1] John Bardeen; Leon Cooper; J. R. Schriﬀer (Decem- at helium temperatures”. Commun. Phys. Lab. Univ. ber 1, 1957). “Theory of Superconductivity”. Physi- Leiden 12: 120. cal Review 8 (5): 1178. Bibcode:1957PhRv..108.1175B. doi:10.1103/physrev.108.1175. ISBN 9780677000800. [15] Dirk vanDelft & Peter Kes (September 2010). Retrieved June 6, 2014. reprinted in Nikolaĭ Nikolaevich “The Discovery of Superconductivity” (PDF). Physics Bogoliubov (1963) The Theory of Superconductivity, Vol. Today (American Institute of Physics) 63: 38–43. 4, CRC Press, ISBN 0677000804, p. 73 doi:10.1063/1.3490499.

[2] John Daintith (2009). The Facts on File Dictionary of [16] W. Meissner & R. Ochsenfeld (1933). “Ein neuer Eﬀekt Physics (4th ed.). Infobase Publishing. p. 238. ISBN bei Eintritt der Supraleitfähigkeit”. Naturwissenschaften 1438109490. 21 (44): 787–788. Bibcode:1933NW.....21..787M. doi:10.1007/BF01504252. [3] John C. Gallop (1990). SQUIDS, the Josephson Eﬀects and Superconducting Electronics. CRC Press. pp. 3, 20. ISBN [17] F. London & H. London (1935). “The Elec- 0-7503-0051-5. tromagnetic Equations of the Supraconductor”. Proceedings of the Royal Society of London A 149 [4] Durrant, Alan (2000). Quantum Physics of Matter. CRC (866): 71–88. Bibcode:1935RSPSA.149...71L. Press. pp. 102–103. ISBN 0750307218. doi:10.1098/rspa.1935.0048. JSTOR 96265.

[5] J. G. Bednorz & K. A. Müller (1986). “Possible high Tc [18] Meissner, W.; R. Ochsenfeld (1933). “Ein neuer Eﬀekt superconductivity in the Ba−La−Cu−O system”. Z. Phys. bei Eintritt der Supraleitfähigkeit”. Naturwissenschaften B 64 (1): 189–193. Bibcode:1986ZPhyB..64..189B. 21 (44): 787–788. Bibcode:1933NW.....21..787M. doi:10.1007/BF01303701. doi:10.1007/BF01504252. 1.8. REFERENCES 9

[19] “The London equations”. The Open University. Re- [32] T.G. Berlincourt (1987). “Emergence of Nb-Ti as trieved 2011-10-16. Supermagnet Material”. Cryogenics 27 (6): 283– 289. Bibcode:1987Cryo...27..283B. doi:10.1016/0011- [20] J. Bardeen; L. N. Cooper & J. R. Schrieffer (1957).“Mi- 2275(87)90057-9. croscopic Theory of Superconductivity”. Physical Re- view 106 (1): 162–164. Bibcode:1957PhRv..106..162B. [33] B. D. Josephson (1962). “Possible new effects in su- doi:10.1103/PhysRev.106.162. perconductive tunnelling”. Physics Letters 1 (7): 251– 253. Bibcode:1962PhL.....1..251J. doi:10.1016/0031- [21] J. Bardeen; L. N. Cooper & J. R. Schrieffer (1957). 9163(62)91369-0. “Theory of Superconductivity”. Physical Review 108 (5): 1175–1205. Bibcode:1957PhRv..108.1175B. [34] “Newly discovered fundamental state of matter, a su- doi:10.1103/PhysRev.108.1175. perinsulator, has been created.”. Science Daily. April 9, 2008. Retrieved 2008-10-23. [22] V. L. Ginzburg & L.D. 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Retrieved 9 October 2012. doi:10.1103/PhysRev.78.487. [38] Alexei A. Abrikosov (8 December 2003). “type II Su- [25] N. N. Bogoliubov (1958). “A new method in the the- perconductors and the Vortex Lattice”. Nobel Lecture. ory of superconductivity”. Zhurnal Eksperimental'noi i Teoreticheskoi Fiziki 34: 58. [39] Adam Mann (Jul 20, 2011). “High-temperature superconductivity at 25: Still in suspense”. Nature [26] L. P. Gor'kov (1959). “Microscopic derivation of the 475 (7356): 280–2. Bibcode:2011Natur.475..280M. Ginzburg̶Landau equations in the theory of supercon- doi:10.1038/475280a. PMID 21776057. ductivity”. Zhurnal Eksperimental'noi i Teoreticheskoi Fiziki 36: 1364. [40] Pines, D. (2002), “The Spin Fluctuation Model for High Temperature Superconductivity: Progress and Prospects” [27] M. Combescot; W.V. Pogosov and O. Betbeder- , The Gap Symmetry and Fluctuations in High-Tc Super- Matibet (2013). “BCS ansatz for superconduc- conductors, NATO Science Series: B: 371, New York: tivity in the light of the Bogoliubov approach Kluwer Academic, pp. 111–142, doi:10.1007/0-306- and the Richardson–Gaudin exact wave func- 47081-0_7, ISBN 0-306-45934-5 tion”. Physica C: Superconductivity 485: 47–57. arXiv:1111.4781. Bibcode:2013PhyC..485...47C. [41] P. Monthoux; A. V. Balatsky & D. Pines (1991). doi:10.1016/j.physc.2012.10.011. Retrieved 11 August “Toward a theory of high-temperature supercon- 2014. ductivity in the antiferromagnetically correlated cuprate oxides”. Phys. Rev. Lett. 67 (24): [28] Buck, Dudley A. “The Cryotron - A Superconductive 3448–3451. Bibcode:1991PhRvL..67.3448M. Computer Component”(PDF). Lincoln Laboratory, Mas- doi:10.1103/PhysRevLett.67.3448. PMID 10044736. sachusetts Institute of Technology. Retrieved 10 August 2014. [42] A. Schilling; et al. (1993). “Superconductivity above 130 K in the Hg–Ba–Ca–Cu–O system”. Nature [29] G.B.Yntema (1955). “Superconducting Wind- 363 (6424): 56–58. Bibcode:1993Natur.363..56C. ing for Electromagnet”. Physical Review doi:10.1038/363056a0. 98 (4): 1197. Bibcode:1955PhRv...98.1144.. doi:10.1103/PhysRev.98.1144. [43] P. Dai; B. C. Chakoumakos; G. F. Sun; K. W. Wong; et al. (1995). “Synthesis and neutron powder diffrac- [30] J.E. Kunzler, E. Buehler, F.L.S. Hsu, and J.H. Wernick tion study of the superconductor HgBa2Ca2Cu3O8+δ (1961). “Superconductivity in Nb3Sn at High Current by Tl substitution”. Physica C 243 (3–4): 201– Density in a Magnetic Field of 88 kgauss”. Physical Re- 206. Bibcode:1995PhyC..243..201D. doi:10.1016/0921- view Letters 6 (3): 89–91. Bibcode:1961PhRvL...6...89K. 4534(94)02461-8. doi:10.1103/PhysRevLett.6.89. [44] Hiroki Takahashi; Kazumi Igawa; Kazunobu Arii; Yoichi [31] T.G. Berlincourt and R.R. Hake (1962). “Pulsed- Kamihara; et al. (2008). “Superconductivity at 43 K in Magnetic-Field Studies of Superconducting Transition an iron-based layered compound LaO1−xFₓFeAs”. Nature Metal Alloys at High and Low Current Densities”. Bul- 453 (7193): 376–378. Bibcode:2008Natur.453..376T. letin of the American Physical Society II–7: 408. doi:10.1038/nature06972. PMID 18432191. 10 CHAPTER 1. SUPERCONDUCTIVITY

[45] Adrian Cho. “Second Family of High-Temperature Su- • Michael Tinkham (2004). Introduction to Supercon- perconductors Discovered”. ScienceNOW Daily News. ductivity (2nd ed.). Dover Books. ISBN 0-486- 43503-2. [46] Zhi-An Ren; et al. (2008). “Superconductiv- ity and phase diagram in iron-based arsenic-oxides • Terry Orlando; Kevin Delin (1991). Foundations ReFeAsO1-d (Re = rare-earth metal) without ﬂuo- of Applied Superconductivity. Prentice Hall. ISBN rine doping”. EPL 83: 17002. arXiv:0804.2582. 978-0-201-18323-8. Bibcode:2008EL.....8317002R. doi:10.1209/0295- 5075/83/17002. • Paul Tipler; Ralph Llewellyn (2002). Modern Physics (4th ed.). W. H. Freeman. ISBN 0-7167- [47] Li, Yinwei; Hao, Jian; Liu, Hanyu; Li, Yanling; Ma, Yan- 4345-0. ming (2014-05-07).“The metallization and superconductivity of dense hydrogen sulﬁde”. The Journal of Chem- ical Physics 140 (17): 174712. doi:10.1063/1.4874158. ISSN 0021-9606. 1.10 External links

[48] Drozdov, A. P.; Eremets, M. I.; Troyan, I. A.; Kseno- • Everything about superconductivity: properties, re- fontov, V.; Shylin, S. I. (2015). “Conventional su- search, applications with videos, animations, games perconductivity at 203 kelvin at high pressures in the sulfur hydride system”. Nature 525 (7567): 73–6. • Video about Type I Superconductors: doi:10.1038/nature14964. ISSN 0028-0836. PMID R=0/transition temperatures/ B is a state vari- 26280333. able/ Meissner eﬀect/ Energy gap(Giaever)/ BCS model [49] Islam; et al. (2014). “A review of oﬀshore wind tur- bine nacelle: Technical challenges, and research and de- • Superconductivity: Current in a Cape and Ther- ” velopmental trends. . Renewable and Sustainable Energy mal Tights. An introduction to the topic for non- Reviews 33: 161–176. doi:10.1016/j.rser.2014.01.085. scientists National High Magnetic Field Laboratory

[50] Linder, Jacob; Robinson, Jason W. A. (2 April 2015). • Lectures on Superconductivity (series of videos, in- “Superconducting spintronics”. Nature Physics 11 (4): cluding interviews with leading experts) 307–315. doi:10.1038/nphys3242. • Superconductivity News Update [51] Thomas; et al. (2016). “Superconducting transmission lines – Sustainable electric energy transfer with higher • Superconductor Week Newsletter – industry news, public acceptance?". Renewable and Sustainable Energy links, et cetera Reviews 55: 59–72. doi:10.1016/j.rser.2015.10.041. • Superconducting Magnetic Levitation [52] “All Nobel Prizes in Physics”. Nobelprize.org. Nobel Media AB 2014. • National Superconducting Cyclotron Laboratory at Michigan State University

• YouTube Video Levitating magnet 1.9 Further reading • International Workshop on superconductivity in Di- • Hagen Kleinert (1989). “Superﬂow and Vortex amond and Related Materials (free download pa- Lines”. Gauge Fields in Condensed Matter 1. World pers) Scientiﬁc. ISBN 9971-5-0210-0. • New Diamond and Frontier Carbon Technology Volume 17, No.1 Special Issue on Superconductiv- • Anatoly Larkin; Andrei Varlamov (2005). Theory ity in CVD Diamond of Fluctuations in Superconductors. Oxford Univer- sity Press. ISBN 0-19-852815-9. • DoITPoMS Teaching and Learning Package –“Su- perconductivity” • A. G. Lebed (2008). The Physics of Organic Super- conductors and Conductors 110 (1st ed.). Springer. • The Nobel Prize for Physics, 1901–2008 ISBN 978-3-540-76667-4. • folding hands-on activities about superconductivity • Jean Matricon; Georges Waysand; Charles Glashausser (2003). The Cold Wars: A History of Superconductivity. Rutgers University Press. ISBN 0-8135-3295-7.

• “Physicist Discovers Exotic Superconductivity”. ScienceDaily. 17 August 2006. Chapter 2

Meissner eﬀect

strength of the applied field rises above a critical value B B Hc. Depending on the geometry of the sample, one may obtain an intermediate state*[2] consisting of a baroque pattern*[3] of regions of normal material carrying a magnetic field mixed with regions of superconducting material containing no field. In Type II superconductors, raising the applied field past a critical value Hc1 leads to a mixed state (also known as the vortex state) in which an increasing amount of magnetic flux penetrates the material, but there remains no resistance to the flow of electric current as long as the current is not too large. At a second critical field strength Hc2, superconductivity is destroyed. The mixed state is actually caused by vortices in the electronic superfluid, sometimes called fluxons because the flux carried by these vortices is quantized. Most pure TTc c nanotubes, are Type I, while almost all impure and compound superconductors are Type II. Diagram of the Meissner effect. Magnetic field lines, represented as arrows, are excluded from a superconductor when it is below its critical temperature. 2.1 Explanation

The Meissner effect was given a phenomenological ex- The Meissner effect is the expulsion of a magnetic field planation by the brothers Fritz and Heinz London, who from a superconductor during its transition to the super- showed that the electromagnetic free energy in a superconducting state. The German physicists Walther Meiss- conductor is minimized provided ner and Robert Ochsenfeld discovered this phenomenon in 1933 by measuring the magnetic field distribution out- side superconducting tin and lead samples.*[1] The sam- ∇2H = λ−2H ples, in the presence of an applied magnetic field, were where H is the magnetic field and λ is the London pene- cooled below their superconducting transition temperature. Below the transition temperature the samples tration depth. cancelled nearly all interior magnetic fields. They de- This equation, which is known as the London equa- tected this effect only indirectly because the magnetic tion, predicts that the magnetic field in a superconductor flux is conserved by a superconductor: when the interior decays exponentially from whatever value it possesses at field decreases, the exterior field increases. The experi- the surface. ment demonstrated for the first time that superconductors In a weak applied field, a superconductor“expels”nearly were more than just perfect conductors and provided a all magnetic flux. It does this by setting up electric cur- uniquely defining property of the superconducting state. rents near its surface. The magnetic field of these surface A superconductor with little or no magnetic field within currents cancels the applied magnetic field within the bulk it is said to be in the Meissner state. The Meissner state of the superconductor. As the field expulsion, or cancel- breaks down when the applied magnetic field is too large. lation, does not change with time, the currents producing Superconductors can be divided into two classes accord- this effect (called persistent currents) do not decay with ing to how this breakdown occurs. In Type I supercon- time. Therefore, the conductivity can be thought of as ductors, superconductivity is abruptly destroyed when the infinite: a superconductor.

11 12 CHAPTER 2. MEISSNER EFFECT

2.3 Consequences

The discovery of the Meissner effect led to the phenomenological theory of superconductivity by Fritz and Heinz London in 1935. This theory explained resis- tanceless transport and the Meissner effect, and allowed the first theoretical predictions for superconductivity to be made. However, this theory only explained experimental observations̶it did not allow the microscopic origins of the superconducting properties to be identified. This was done successfully by the BCS theory in 1957, from which the penetration depth and the Meissner effect result.*[4] However, some physicists argue that BCS A magnet levitating above a superconductor cooled by liquid ni- theory does not explain the Meissner effect.*[5] trogen. • A tin cylinder̶in a Dewar flask filled with liquid he- Near the surface, within the London penetration depth, lium̶has been placed between the poles of an elec- the magnetic field is not completely cancelled. Each su- tromagnet. The magnetic field is about 8 millitesla perconducting material has its own characteristic pene- (80 G). tration depth. • T=4.2 K, B=8 mT (80 G). Tin is in the normally Any perfect conductor will prevent any change to mag- conducting state. The compass needles indicate that netic flux passing through its surface due to ordinary magnetic flux permeates the cylinder. electromagnetic induction at zero resistance. The Meiss- ner effect is distinct from this: when an ordinary conduc- • The cylinder has been cooled from 4.2 K to 1.6 K. tor is cooled so that it makes the transition to a supercon- The current in the electromagnet has been kept conducting state in the presence of a constant applied mag- stant, but the tin became superconducting at about 3 netic field, the magnetic flux is expelled during the tran- K. Magnetic flux has been expelled from the cylin- sition. This effect cannot be explained by infinite con- der (the Meissner effect). ductivity alone. Its explanation is more complex and was first given in the London equations by the brothers Fritz and Heinz London. It should thus be noted that the placement and subsequent levitation of a magnet above an al- 2.4 Paradigm for the Higgs mecha- ready superconducting material does not demonstrate the nism Meissner effect, while an initially stationary magnet later being repelled by a superconductor as it is cooled through its critical temperature does. The Meissner effect of superconductivity serves as an important paradigm for the generation mechanism of a mass M (i.e. a reciprocal range, λM := h/(Mc) where h is Planck constant and c is speed of light) for 2.2 Perfect diamagnetism a gauge field. In fact, this analogy is an abelian example for the Higgs mechanism,*[6] through which in high- Superconductors in the Meissner state exhibit perfect dia- energy physics the masses of the electroweak gauge par- magnetism, or superdiamagnetism, meaning that the to- ticles, W± and Z are generated. The length λM is iden- tal magnetic field is very close to zero deep inside them tical with the London penetration depth in the theory of (many penetration depths from the surface). This means superconductivity.*[7]*[8] that their magnetic susceptibility, χv = −1. Diamagnetics are defined by the generation of a spontaneous magnetization of a material which directly opposes the direction 2.5 See also of an applied field. However, the fundamental origins of diamagnetism in superconductors and normal materials are very different. In normal materials diamagnetism • Superfluid arises as a direct result of the orbital spin of electrons about the nuclei of an atom induced electromagnetically • Type-I superconductor by the application of an applied field. In superconductors the illusion of perfect diamagnetism arises from persis- • Type-II superconductor tent screening currents which flow to oppose the applied field (the Meissner effect); not solely the orbital spin. • Flux pinning 2.8. EXTERNAL LINKS 13

2.6 References responsible for the Meissner effect, in the case of a long magnet levitated above a superconducting [1] Meissner, W.; R. Ochsenfeld (1933). “Ein neuer Effekt plane. bei Eintritt der Supraleitfähigkeit”. Naturwissenschaften 21 (44): 787–788. Bibcode:1933NW.....21..787M. • Michael Tinkham (2004). Introduction to Supercon- doi:10.1007/BF01504252. ductivity. Dover Books on Physics (2nd ed.). ISBN 978-0-486-43503-9.. A good technical reference. [2] Lev D. Landau; Evgeny M. Lifschitz (1984). Electro- dynamics of Continuous Media. Course of Theoretical Physics 8. Oxford: Butterworth-Heinemann. ISBN 0- 7506-2634-8. 2.8 External links “ [3] David J. E. Callaway (1990). On the remark- • able structure of the superconducting intermedi- Maglev Trains Audio slideshow from the National ate state”. Nuclear Physics B 344 (3): 627–645. High Magnetic Field Laboratory discusses magnetic Bibcode:1990NuPhB.344..627C. doi:10.1016/0550- levitation, the Meissner Effect, magnetic flux trap- 3213(90)90672-Z. ping and superconductivity. [4] J. Bardeen; L. N. Cooper; J. R. Schrieffer (1957). • Meissner Effect (Science from scratch) Short video “Theory of superconductivity” (PDF). Physical Review from Imperial College London about the Meissner B 106 (1175): 162–164. Bibcode:1957PhRv..106..162B. effect and levitating trains of the future. doi:10.1103/physrev.106.162. • Introduction to superconductivity Video about Type [5] J.E Hirsch (2012). “The origin of the Meissner effect in new and old superconductors”. Physica 1 Superconductors: R=0/Transition temperatures/B Scripta 85: 035704. Bibcode:2012PhyS...85a5704P. is a state variable/Meissner effect/Energy gap (Gi- doi:10.1088/0031-8949/85/01/015704. aever)/BCS model. [6] P. W. Higgs (1966). “Spontaneous Sym- • Meissner Effect (Hyperphysics) metry Breakdown without Massless Bosons” . Phys. Rev. 145 (4): 1156. arXiv:cond- • Historical Background of the Meissner Effect mat/0305542. Bibcode:2003PhLA..315..474H. doi:10.1103/PhysRev.145.1156. [7] Wilczek, F. (2000). “The recent excite- ment in high-density QCD”. Nuclear Physics A 663: 257–271. arXiv:hep-ph/9908480. Bibcode:2000NuPhA.663..257W. doi:10.1016/S0375- 9474(99)00601-6. [8] Weinberg, S. (1986). “Superconductivity for particular theorists”. Prog. Theor. Phys. Sup- plement 86: 43–53. Bibcode:1986PThPS..86...43W. doi:10.1143/PTPS.86.43.

2.7 Further reading

• Albert Einstein (1922). “Theoreti- cal remark on the superconductivity of metals”. arXiv:physics/0510251v2. Bibcode:2005physics..10251E. • Fritz Wolfgang London (1950).“Macroscopic The- ory of Superconductivity”. Superfluids. Structure of matter series 1. OCLC 257588418.. Revised 2nd edition, Dover (1960) ISBN 978-0-486-60044- 4. By the man who explained the Meissner effect. pp. 34–37 gives a technical discussion of the Meiss- ner effect for a superconducting sphere. • Wayne M. Saslow (2002). Electricity, Magnetism, and Light. Academic. ISBN 978-0-12-619455- 5. OCLC 51032778.. pp. 486–489 gives a simple mathematical discussion of the surface currents Chapter 3

Technological applications of superconductivity

Some of the technological applications of required for MRI and NMR. This represents a multi- superconductivity include: billion US$ market for companies such as Oxford In- struments and Siemens. The magnets typically use • the production of sensitive magnetometers based on low temperature superconductors (LTS) because high- SQUIDs temperature superconductors are not yet cheap enough to cost-effectively deliver the high, stable and large volume • fast digital circuits (including those based on fields required, notwithstanding the need to cool LTS in- Josephson junctions and rapid single flux quantum struments to liquid helium temperatures. Superconduc- technology), tors are also used in high field scientific magnets.

• powerful superconducting electromagnets used in maglev trains, Magnetic Resonance Imaging (MRI) 3.2 Particle accelerators and mag- and Nuclear magnetic resonance (NMR) machines, magnetic confinement fusion reactors (e.g. netic fusion devices tokamaks), and the beam-steering and focusing magnets used in particle accelerators Particle accelerators such as the Large Hadron Collider can include many high field electromagnets requiring • low-loss power cables large quantities of LTS. To construct the LHC magnets required more than 28 percent of the worldʼs niobium- • RF and microwave filters (e.g., for mobile titanium wire production for five years, with large quan- phone base stations, as well as military ultra- tities of NbTi also used in the magnets for the LHCʼs sensitive/selective receivers) huge experiment detectors.*[2] • fast fault current limiters A small number of magnetic fusion devices (mostly tokamaks) have used SC coils. The current construction • high sensitivity particle detectors, including of ITER has required unprecedented amounts of LTS (eg. the transition edge sensor, the superconducting 500 tonnes, causing a 7 fold increase in worlds annual bolometer, the superconducting tunnel junction production capacity).*[3] detector, the kinetic inductance detector, and the superconducting nanowire single-photon detector 3.3 High-temperature supercon- • railgun and coilgun magnets ductivity (HTS) • electric motors and generators*[1] The commercial applications so far for high temperature superconductors (HTS) have been limited. 3.1 Magnetic Resonance Imaging HTS can superconduct at temperatures above the boiling (MRI) and Nuclear Magnetic point of liquid nitrogen, which makes them cheaper to cool than low temperature superconductors (LTS). How- Resonance (NMR) ever, the problem with HTS technology is that the currently known high temperature superconductors are brit- The biggest application for superconductivity is in pro- tle ceramics which are expensive to manufacture and ducing the large volume, stable, and high magnetic fields not easily formed into wires or other useful shapes.*[4]

14 3.4. NOTES 15

Therefore the applications for HTS have been where it reducing the costly right-of-way required to deliver has some other intrinsic advantage, e.g. in additional power.*[6]

• low thermal loss current leads for LTS devices (low 3.3.3 Tres Amigas Project thermal conductivity),

• RF and microwave filters (low resistance to RF), and American Superconductor was chosen for The Tres Ami- gas Project, the United Statesʼfirst renewable energy mar- • increasingly in specialist scientific magnets, particu- ket hub.*[7] The Tres Amigas renewable energy market larly where size and electricity consumption are crit- hub will be a multi-mile, triangular electricity pathway ical (while HTS wire is much more expensive than of superconductor electricity pipelines capable of trans- LTS in these applications, this can be offset by the ferring and balancing many gigawatts of power between relative cost and convenience of cooling); the abil- three U.S. power grids (the Eastern Interconnection, the ity to ramp field is desired (the higher and wider Western Interconnection and the Texas Interconnection). range of HTS's operating temperature means faster Unlike traditional powerlines, it will transfer power as DC changes in field can be managed); or cryogen free instead of AC current. It will be located in Clovis, New operation is desired (LTS generally requires liquid Mexico. helium that is becoming more scarce and expensive). 3.3.4 Magnesium diboride

3.3.1 HTS-based systems Magnesium diboride is a much cheaper superconductor than either BSCCO or YBCO in terms of cost per HTS has application in scientific and industrial magnets, current-carrying capacity per length (cost/(kA*m)), in including use in NMR and MRI systems. Commercial the same ballpark as LTS, and on this basis many manu- systems are now available in each category.*[5] factured wires are already cheaper than copper. Further- Also one intrinsic attribute of HTS is that it can with- more, MgB2 superconducts at temperatures higher than stand much higher magnetic fields than LTS, so HTS at LTS (its critical temperature is 39 K, compared with less liquid helium temperatures are being explored for very than 10 K for NbTi and 18.3 K for Nb3Sn), introducing high-field inserts inside LTS magnets. the possibility of using it at 10-20 K in cryogen-free magnets or perhaps eventually in liquid hydrogen. However Promising future industrial and commercial HTS ap- MgB2 is limited in the magnetic field it can tolerate at plications include Induction heaters, transformers, fault these higher temperatures, so further research is required current limiters, power storage, motors and generators, to demonstrate its competitiveness in higher field appli- fusion reactors (see ITER) and magnetic levitation de- cations. vices. Early applications will be where the benefit of smaller size, lower weight or the ability to rapidly switch current 3.4 Notes (fault current limiters) outweighs the added cost. Longer- term as conductor price falls HTS systems should be com- [1] Fischer, Martin. New Path to 10 MW Renewable Energy petitive in a much wider range of applications on energy World, 12 October 2010. Retrieved: 14 October 2010. efficiency grounds alone. (For a relatively technical and US-centric view of state of play of HTS technology in [2] Superconductors Face the Future. 2010 power systems and the development status of Genera- [3] ITER Magnets tion 2 conductor see Superconductivity for Electric Sys- tems 2008 US DOE Annual Peer Review.) [4] See for example L. R. Lawrence et al: “High Tempera- ture Superconductivity: The Products and their Benefits” (2002) Bob Lawrence & Associates, Inc. 3.3.2 Holbrook Superconductor Project [5] See for example HTS-110 Ltd and Paramed Medical Sys- tems . The Holbrook Superconductor Project is a project to design and build the world's first production [6] Gelsi, Steve (2008-07-10). “Power firms grasp new tech superconducting transmission power cable. The ca- for aging grid”. Market Watch. Retrieved 2008-07-11. ble was commissioned in late June 2008. The suburban [7] “Superconductor Electricity Pipelines to be Adopted for Long Island electrical substation is fed by about 600- America's First Renewable Energy Market Hub”. 2009- meter-long underground cable system consists of about 10-13. Retrieved 2009-10-25. 99 miles of high-temperature superconductor wire manufactured by American Superconductor, installed underground and chilled with liquid nitrogen greatly Chapter 4

SQUID

For other uses, see Squid (disambiguation). 4.1.1 DC SQUID A SQUID (for superconducting quantum interfer-

Ia I I Φ

Diagram of a DC SQUID. The current I enters and splits into the two paths, each with currents Ia and Ib . The thin barriers on each path are Josephson junctions, which together separate the two superconducting regions. Φ represents the magnetic flux Sensing element of the SQUID threading the DC SQUID loop. ence device) is a very sensitive magnetometer used to measure extremely subtle magnetic fields, based on superconducting loops containing Josephson junctions. SQUIDs are sensitive enough to measure fields as low as 5 aT (5×10*−18 T) within a few days of averaged measurements.*[1] Their noise levels are as low as 3 fT·Hz*- ½.*[2] For comparison, a typical refrigerator magnet produces 0.01 tesla (10*−2 T), and some processes in ani- mals produce very small magnetic fields between 10*−9 T and 10*−6 T. Recently invented SERF atomic magnetometers are potentially more sensitive and do not require cryogenic refrigeration but are orders of magnitude larger Electrical schematic of a SQUID where Ib is the bias current, I0 3 in size (~1 cm ) and must be operated in a near-zero magis the critical current of the SQUID, Φ is the flux threading the netic field. SQUID and V is the voltage response to that flux. The X-symbols represent Josephson junctions.

The DC SQUID was invented in 1964 by Robert Jakle- 4.1 History and design vic, John J. Lambe, James Mercereau, and Arnold Sil- ver of Ford Research Labs*[3] after Brian David Joseph- There are two main types of SQUID: direct current son postulated the Josephson effect in 1962, and the first (DC) and radio frequency (RF). RF SQUIDs can work Josephson junction was made by John Rowell and Philip with only one Josephson junction (superconducting tun- Anderson at Bell Labs in 1963.*[4] It has two Joseph- nel junction), which might make them cheaper to pro- son junctions in parallel in a superconducting loop. It is duce, but are less sensitive. based on the DC Josephson effect. In the absence of any

16 4.1. HISTORY AND DESIGN 17

loops with a large self-inductance. According to the re- lations, given above, this implies also small current and voltage variations. In practice the self-inductance L of the loop is not so large. The general case can be evalu- ated by introducing a parameter

i L λ = c Φ0 Left: Plot of current vs. voltage for a SQUID. Upper and lower curves correspond to nΦ0 and (n+1/2)Φ0 respectively. Right: with ic the critical current of the SQUID. Usually λ is of Periodic voltage response due to flux through a SQUID. The pe- order one.*[7] riodicity is equal to one flux quantum, Φ0 4.1.2 RF SQUID external magnetic field, the input current I splits into the two branches equally. If a small external magnetic field is applied to the superconducting loop, a screening current, Is , begins circulating in the loop that generates a magnetic field canceling the applied external flux. The induced current is in the same direction as I in one of the branches of the superconducting loop, and is opposite to I in the other branch; the total current becomes I/2 + Is in one branch and I/2 − Is in the other. As soon as the current in either branch exceeds the critical current, Ic , of the Josephson junction, a voltage appears across the junction. Now suppose the external flux is further increased until it exceeds Φ0/2 , half the magnetic flux quantum. Since the flux enclosed by the superconducting loop must be an integer number of flux quanta, instead of screening the flux the SQUID now energetically prefers to increase it A prototype SQUID to Φ0 . The screening current now flows in the opposite direction. Thus the screening current changes direction The RF SQUID was invented in 1965 by Robert Jaklevic, every time the flux increases by half integer multiples of John J. Lambe, Arnold Silver, and James Edward Zim- Φ0 . Thus the critical current oscillates as a function of merman at Ford.*[6] It is based on the AC Josephson ef- the applied flux. If the input current is more than Ic , then fect and uses only one Josephson junction. It is less sen- the SQUID always operates in the resistive mode. The sitive compared to DC SQUID but is cheaper and easier voltage in this case is thus a function of the applied mag- to manufacture in smaller quantities. Most fundamental netic field and the period equal to Φ0 . Since the current- measurements in biomagnetism, even of extremely small voltage characteristics of the DC SQUID is hysteretic, signals, have been made using RF SQUIDS.*[8]*[9] The a shunt resistance, R is connected across the junction to RF SQUID is inductively coupled to a resonant tank cir- eliminate the hysteresis (in the case of copper oxide based cuit. Depending on the external magnetic field, as the high-temperature superconductors the junction's own in- SQUID operates in the resistive mode, the effective intrinsic resistance is usually sufficient). The screening cur- ductance of the tank circuit changes, thus changing the rent is the applied flux divided by the self-inductance of resonant frequency of the tank circuit. These frequency the ring. Thus ∆Φ can be estimated as the function of * * measurements can be easily taken, and thus the losses ∆V (flux to voltage converter) [5] [6] as follows: which appear as the voltage across the load resistor in the circuit are a periodic function of the applied magnetic flux ∆V = R ∆I with a period of Φ0. For a precise mathematical description refer to the original paper by Erné et al.*[5]*[10] 2I = 2 ∆Φ/L, where L is the self inductance of the superconducting ring 4.1.3 Materials used

∆V = (R/L) ∆Φ The traditional superconducting materials for SQUIDs are pure niobium or a lead alloy with 10% gold or indium, The discussion in this Section assumed perfect ﬂux quan- as pure lead is unstable when its temperature is repeat- tization in the loop. However, this is only true for big edly changed. To maintain superconductivity, the entire 18 CHAPTER 4. SQUID

device needs to operate within a few degrees of absolute the surface of a sample and the local magnetic flux.*[14] zero, cooled with liquid helium. For example, SQUIDs are being used as detectors to per- In 2006, proof of concept has be shown for CNT-SQUID form magnetic resonance imaging (MRI). While high- sensors build with Aluminum (for the loop) and single field MRI uses precession fields of one to several tes- walled carbon nanotube (CNT).*[11] The sensors is few las, SQUID-detected MRI uses measurement fields that 100 nm size and operates at 1K or below . Such sensors lie in the microtesla range. In a conventional MRI sys- allows to count spins.*[12] tem, the signal scales as the square of the measurement High-temperature SQUID sensors are more recent; they frequency (and hence precession field): one power of fre- are made of high-temperature superconductors, partic- quency comes from the thermal polarization of the spins ularly YBCO, and are cooled by liquid nitrogen which at ambient temperature, while the second power of field is cheaper and more easily handled than liquid helium. comes from the fact that the induced voltage in the pickup They are less sensitive than conventional low temperature coil is proportional to the frequency of the precessing SQUIDs but good enough for many applications. magnetization. In the case of untuned SQUID detection of prepolarized spins, however, the NMR signal strength is independent of precession field, allowing MRI signal detection in extremely weak fields, of order the Earth's 4.2 Uses field. SQUID-detected MRI has advantages over high- field MRI systems, such as the low cost required to build such a system, and its compactness. The principle has been demonstrated by imaging human extremities, and its future application may include tumor screening.*[15] Another application is the scanning SQUID microscope, which uses a SQUID immersed in liquid helium as the probe. The use of SQUIDs in oil prospecting, mineral exploration, earthquake prediction and geothermal energy surveying is becoming more widespread as superconductor technology develops; they are also used as pre- cision movement sensors in a variety of scientific applications, such as the detection of gravitational waves.*[16] A SQUID is the sensor in each of the four gyroscopes em- The inner workings of an early SQUID ployed on Gravity Probe B in order to test the limits of the theory of general relativity.*[1] The extreme sensitivity of SQUIDs makes them ideal for A modified RF SQUID was used to observe the studies in biology. Magnetoencephalography (MEG), for dynamical Casimir effect for the first time.*[17]*[18] example, uses measurements from an array of SQUIDs SQUIDS are used in finding a submerged submarine ..ra- to make inferences about neural activity inside brains. dio waves nor light penetrates more than few metres into Because SQUIDs can operate at acquisition rates much sea water.sound travels further than light but changes den- higher than the highest temporal frequency of interest in sity of water reflect back sound waves.the problem boils the signals emitted by the brain (kHz), MEG achieves down to one of transparency. To magnetism ,sea water good temporal resolution. Another area where SQUIDs remains crystal clear.submarines have lots of iron laden are used is magnetogastrography, which is concerned steel..so presence of ferromagnetic material strongly dis- with recording the weak magnetic fields of the stomach. trort the earth magnetic field as submarines passes by.. A novel application of SQUIDs is the magnetic marker monitoring method, which is used to trace the path of orally applied drugs. In the clinical environment SQUIDs 4.2.1 Proposed uses are used in cardiology for magnetic field imaging (MFI), which detects the magnetic field of the heart for diagnosis It has also been suggested that they might be implemented and risk stratification. in a quantum computer.*[19] Probably the most common commercial use of SQUIDs A potential military application exists for use in anti- is in magnetic property measurement systems (MPMS). submarine warfare as a magnetic anomaly detector These are turn-key systems, made by several manufac- (MAD) fitted to maritime patrol aircraft.*[20] turers, that measure the magnetic properties of a material sample. This is typically done over a temperature range from that of 300 mK to roughly 400 K.*[13] With the decreasing size of SQUID sensors since the last decade, 4.3 See also such sensor can equip the tip of an AFM probe. Such device allows simultaneous measurement of roughness of • Macroscopic quantum phenomena 4.5. REFERENCES 19

• Geophysics [13] Kleiner, R.; Koelle, D.; Ludwig, F.; Clarke, J. (2004). “Superconducting quantum interference devices: State of • Electromagnetism the art and applications”. Proceedings of the IEEE 92 (10): 1534–1548. doi:10.1109/JPROC.2004.833655. • Aharonov–Bohm eﬀect [14] microSQUID microscopy at Institut Néel (Grenoble, FRANCE)

4.4 Notes [15] Clarke, J.; Lee, A.T.; Mück, M.; Richards, P.L.“Chapter 8.3: Nuclear Magnetic and Quadrupole Resonance and [1] Ran, Shannon Kʼdoah (2004). Gravity Probe B: Exploring Magnetic Resonance Imaging”. pp. 56–81. Missing or Einstein's Universe with Gyroscopes (PDF). NASA. p. 26. empty |title= (help) in Clarke & Braginski 2006

[2] D. Drung, C. Assmann, J. Beyer, A. Kirste, M. [16] Paik, Ho J.“Chapter 15.2: Superconducting Transducer Peters, F. Ruede, and Th. Schurig (2007). for Gravitational-Wave Detectors”. pp. 548–554. Miss- “Highly sensitive and easy-to-use SQUID sensors” ing or empty |title= (help) in Clarke & Braginski 2006 (PDF). IEEE Transactions on Applied Superconductiv- ity 17 (2): 699–704. Bibcode:2007ITAS...17..699D. [17] “First Observation of the Dynamical Casimir Eﬀect”. doi:10.1109/TASC.2007.897403. Technology Review.

[3] R. C. Jaklevic, J. Lambe, A. H. Silver, and J. [18] Wilson, C. M. (2011). “Observation of the E. Mercereau (1964). “Quantum Interference Ef- Dynamical Casimir Eﬀect in a Superconduct- fects in Josephson Tunneling”. Phys. Rev. Let- ing Circuit”. Nature 479 (7373): 376–379. ters 12 (7): 159–160. Bibcode:1964PhRvL..12..159J. arXiv:1105.4714. Bibcode:2011Natur.479..376W. doi:10.1103/PhysRevLett.12.159. doi:10.1038/nature10561. PMID 22094697.

[4] Anderson, P.; Rowell, J. (1963). “Probable [19] Quantum coherence with a single Cooper pair, V Bouch- Observation of the Josephson Superconducting iat, D Vion, P Joyez, D Esteve, M H Devoret, 1998 Phys. Tunneling Eﬀect”. Physical Review Letters 10 Scr. 1998 165 (6): 230–232. Bibcode:1963PhRvL..10..230A. doi:10.1103/PhysRevLett.10.230. [20] Ouellette, Jennifer. “SQUID Sensors Penetrate New Markets” (PDF). The Industrial Physicist. p. 22. [5] E. du Trémolet de Lacheisserie, D. Gignoux, and M. Archived from the original (PDF) on 18 May 2008. Schlenker (editors) (2005). Magnetism: Materials and Applications 2. Springer.

[6] J. Clarke and A. I. Braginski (Eds.) (2004). The SQUID 4.5 References handbook 1. Wiley-Vch. • [7] A.TH.A.M. de Waele and R. de Bruyn Ouboter (1969). Clarke, John; Braginski, Alex I., eds. (2006). “Quantum-interference phenomena in point contacts be- The SQUID Handbook: Applications of SQUIDs and tween two superconductors”. Physica 41 (2): 225– SQUID Systems 2. Wiley-VCH. ISBN 978-3-527- 254. Bibcode:1969Phy....41..225D. doi:10.1016/0031- 40408-7. 8914(69)90116-5.

[8] Romani, G. L.; Williamson, S. J.; Kaufman, L. (1982). “Biomagnetic instrumentation”. Review of Scientiﬁc In- struments 53 (12): 1815–1845. doi:10.1063/1.1136907. PMID 6760371.

[9] Sternickel, K.; Braginski, A. I. (2006). “Biomagnetism using SQUIDs: Status and perspectives”. Superconductor Science and Technology 19 (3): S160. doi:10.1088/0953- 2048/19/3/024.

[10] S.N. Erné, H.-D. Hahlbohm, H. Lübbig (1976).“Theory of the RF biased Superconducting Quantum Interference Device for the non-hysteretic regime”. J. Appl. Phys. 47 (12): 5440–5442. Bibcode:1976JAP....47.5440E. doi:10.1063/1.322574.

[11] Cleuziou, J.-P.; Wernsdorfer, W. (2006). “Car- bon nanotube superconducting quantum interference device”. Nature Nanotechnology 1 (October): 53–9. doi:10.1038/nnano.2006.54. PMID 18654142.

[12] Aprili, Marco (2006).“The nanoSQUID makes its debut” . Nature Nanotechnology 1 (October). Chapter 5

Maglev

This article is about transportation using magnetic levita- Maglev trains move more smoothly and more quietly than tion. For other uses, see Maglev (disambiguation). wheeled mass transit systems. They are relatively unaf- Maglev (derived from magnetic levitation) is a trans- fected by weather. The power needed for levitation is typically not a large percentage of its overall energy consumption;*[3] most goes to overcome drag, as with other high-speed transport. Maglev trains hold the speed record for trains. Compared to conventional (normal) trains, differences in construction affect the economics of maglev trains, making them much more efficient. For high-speed trains with wheels, wear and tear from friction along with the“ham- mer effect”from wheels on rails accelerates equipment wear and prevents high speeds.*[4] Conversely, maglev systems have been much more expensive to construct, off- SCMaglev test track in the Yamanashi Prefecture, Japan setting lower maintenance costs. Despite decades of research and development, only two commercial maglev transport systems are in operation, with two others under construction.*[note 1] In April 2004, Shanghai's Transrapid system began commercial operations. In March 2005, Japan began operation of its relatively low-speed HSST "Linimo" line in time for the 2005 World Expo. In its first three months, the Lin- imo line carried over 10 million passengers. South Korea became the world's second country to succeed in commercializing maglev technology with the Incheon Airport Maglev beginning commercial operation in February 3, 2016.*[5]

Transrapid 09 at the Emsland test facility in Germany 5.1 Development port method that uses magnetic levitation to move vehicles without touching the ground. With maglev, a vehicle In the late 1940s, the British electrical engineer Eric travels along a guideway using magnets to create both lift Laithwaite, a professor at Imperial College London, de- and propulsion, thereby reducing friction by a great extent veloped the ﬁrst full-size working model of the linear in- and allowing very high speeds. duction motor. He became professor of heavy electri- The Shanghai Maglev Train, also known as the cal engineering at Imperial College in 1964, where he Transrapid, is the fastest commercial train currently in continued his successful development of the linear mo- operation and has a top speed of 430 km/h (270 mph). tor.*[6] Since linear motors do not require physical con- The line was designed to connect Shanghai Pudong In- tact between the vehicle and guideway, they became a ternational Airport and the outskirts of central Pudong, common ﬁxture on advanced transportation systems in Shanghai. It covers a distance of 30.5 kilometres (19.0 the 1960s and 70s. Laithwaite joined one such project, mi) in 8 minutes.*[1] The Shanghai system was labeled a the tracked hovercraft, although the project was cancelled white elephant by rivals.*[2] in 1973.*[7]

20 5.2. HISTORY 21

The linear motor was naturally suited to use with maglev 5.2.4 Hamburg, Germany, 1979 systems as well. In the early 1970s, Laithwaite discovered a new arrangement of magnets, the magnetic river, Transrapid 05 was the first maglev train with longsta- that allowed a single linear motor to produce both lift and tor propulsion licensed for passenger transportation. In forward thrust, allowing a maglev system to be built with 1979, a 908 m track was opened in Hamburg for the first a single set of magnets. Working at the British Rail Re- International Transportation Exhibition (IVA 79). In- search Division in Derby, along with teams at several civil terest was sufficient that operations were extended three engineering firms, the “transverse-flux”system was de- months after the exhibition finished, having carried more veloped into a working system. than 50,000 passengers. It was reassembled in Kassel in 1980. The first commercial maglev people mover was simply called "MAGLEV" and officially opened in 1984 near Birmingham, England. It operated on an elevated 5.2.5 Birmingham, United Kingdom, 600-metre (2,000 ft) section of monorail track between Birmingham Airport and Birmingham International rail- 1984–95 way station, running at speeds up to 42 km/h (26 mph). The system was closed in 1995 due to reliability problems.*[8]

5.2 History

5.2.1 First maglev patent

High-speed transportation patents were granted to various inventors throughout the world.*[9] Early United States patents for a linear motor propelled train were awarded to German inventor Alfred Zehden. The inven- The Birmingham International Maglev shuttle tor was awarded U.S. Patent 782,312 (14 February 1905) and U.S. Patent RE12,700 (21 August 1907).*[note 2] In The world's ﬁrst commercial maglev system was a low- 1907, another early electromagnetic transportation sys- speed maglev shuttle that ran between the airport termi- tem was developed by F. S. Smith.*[10] A series of Ger- nal of Birmingham International Airport and the nearby man patents for magnetic levitation trains propelled by Birmingham International railway station between 1984 linear motors were awarded to Hermann Kemper be- and 1995.*[16] Its track length was 600 metres (2,000 ft), tween 1937 and 1941.*[note 3] An early maglev train was and trains levitated at an altitude of 15 millimetres (0.59 described in U.S. Patent 3,158,765, “Magnetic system in), levitated by electromagnets, and propelled with lin- of transportation”, by G. R. Polgreen (25 August 1959). ear induction motors.*[17] It operated for nearly eleven The ﬁrst use of“maglev”in a United States patent was in years, but obsolescence problems with the electronic sys- “Magnetic levitation guidance system”*[11] by Canadian tems made it progressively unreliable as years passed. Patents and Development Limited. One of the original cars is now on display at Railworld in Peterborough, together with the RTV31 hover train 5.2.2 New York, United States, 1913 vehicle. Another is on display at the National Railway Museum in York. Emile Bachelet, of Mount Vernon, N. Y., demonstrated Several favourable conditions existed when the link was a prototype of a magnetic levitating railway car.*[12] built:

• The British Rail Research vehicle was 3 tonnes and 5.2.3 New York, United States, 1968 extension to the 8 tonne vehicle was easy.

In 1968, while delayed in traﬃc on the Throgs Neck • Electrical power was available. Bridge, James Powell, a researcher at Brookhaven Na- • The airport and rail buildings were suitable for ter- tional Laboratory (BNL), thought of using magnetically minal platforms. levitated transportation.*[13] Powell and BNL colleague Gordon Danby worked out a MagLev concept using static • Only one crossing over a public road was required magnets mounted on a moving vehicle to induce electro- and no steep gradients were involved. dynamic lifting and stabilizing forces in specially shaped loops on a guideway.*[14]*[15] • Land was owned by the railway or airport. 22 CHAPTER 5. MAGLEV

• Local industries and councils were supportive. • Some government ﬁnance was provided and because of sharing work, the cost per organization was low.

After the system closed in 1995, the original guideway lay dormant.*[18] It was reused in 2003 when the re- placement cable-hauled AirRail Link Cable Liner people mover was opened.*[19]*[20]

5.2.6 Emsland, Germany, 1984–2012

JNR ML500 at a test track in Miyazaki, Japan, on 21 December 1979 travelled at 517 km/h (321 mph), authorized by Guinness World Records.

1980s continued in Miyazaki before transferring to a far larger test track, 20 km (12 mi) long, in Yamanashi in 1997. Development of HSST started in 1974, based on technologies introduced from Germany. In Tsukuba, Japan (1985), the HSST−03 (Linimo) became popular in spite Transrapid at the Emsland test facility of its 300 km/h (190 mph) at the Tsukuba World Expo- sition. In Saitama, Japan (1988), the HSST-04-1 was re- Main article: Emsland test facility vealed at the Saitama exhibition performed in Kumagaya. Its fastest recorded speed was 300 km/h (190 mph).*[22] Transrapid, a German maglev company, had a test track in Emsland with a total length of 31.5 kilometres (19.6 mi). The single-track line ran between Dörpen and 5.2.8 Vancouver, Canada and Hamburg, Lathen with turning loops at each end. The trains reg- Germany, 1986–88 ularly ran at up to 420 kilometres per hour (260 mph). Paying passengers were carried as part of the testing process. The construction of the test facility began in 1980 and ﬁnished in 1984. In 2006, the Lathen maglev train accident occurred killing 23 people, found to have been caused by human error in implementing safety checks. From 2006 no passengers were carried. At the end of 2011 the operation licence expired and was not renewed, and in early 2012 demolition permission was given for its facilities, including the track and factory.*[21]

5.2.7 Japan, 1969–present

See also: Chūō Shinkansen Japan operates two independently developed maglev trains. One is HSST (and its descendant, the Linimo HSST-03 at Okazaki Minami Park line) by Japan Airlines and the other, which is more well- known, is SCMaglev by the Central Japan Railway Com- Main article: High Speed Surface Transport pany. The development of the latter started in 1969. Miyazaki In Vancouver, Canada, the HSST-03 by HSST Develop- test track regularly hit 517 km/h (321 mph) by 1979. Af- ment Corporation (Japan Airlines and Sumitomo Cor- ter an accident that destroyed the train, a new design was poration) was exhibited at Expo 86*[23] and ran on a selected. In Okazaki, Japan (1987), the SCMaglev took 400-metre (0.25 mi) test track*[24] that provided guests a test ride at the Okazaki exhibition. Tests through the with a ride in a single car along a short section of track 5.3. TECHNOLOGY 23

at the fairgrounds. It was removed after the fair and de- a transfer to the Seoul Metropolitan Subway at AREX's but at the Aoi Expo in 1987 and now on static display at Incheon International Airport Station and is offered free Okazaki Minami Park. of charge to anyone to ride, operating between 9am and * In Hamburg, Germany, the TR-07 was exhibited at the 6pm every 15 minutes. [28] Operating hours are to be international traffic exhibition (IVA88) in 1988. raised in the future. The maglev system was co-developed by the Korea Insti- tute of Machinery and Materials (KIMM) and Hyundai 5.2.9 Berlin, Germany, 1989–91 Rotem.*[29]*[30]*[31] It is 6.1 kilometres (3.8 mi) long, with six stations and a 110 km/h (68 mph) operating Main article: M-Bahn speed.*[32] Two more stages are planned of 9.7 km and 37.4 km. In West Berlin, the M-Bahn was built in the late 1980s. Once completed it will become a circular line. It was a driverless maglev system with a 1.6 km (0.99 Hyundai Rotem is exporting its Maglev technology to mi) track connecting three stations. Testing with passen- Russia's Leningrad MagLev System, the first overseas ger traffic started in August 1989, and regular operation customer who will be getting the first urban commuter started in July 1991. Although the line largely followed a Maglev system in Europe.*[33] new elevated alignment, it terminated at Gleisdreieck U- Bahn station, where it took over an unused platform for a line that formerly ran to East Berlin. After the fall of the Berlin Wall, plans were set in motion to reconnect this 5.3 Technology line (today's U2). Deconstruction of the M-Bahn line began only two months after regular service began. It was See also: SCMaglev § Technology, Transrapid § Tech- called the Pundai project and was completed in February nology and Magnetic levitation 1992. In the public imagination,“maglev”often evokes the con- 5.2.10 South Korea, 1993–present cept of an elevated monorail track with a linear motor. Maglev systems may be monorail or dual rail*[34] and not all monorail trains are maglevs. Some railway trans- Main article: Incheon Airport Maglev port systems incorporate linear motors but use electro- In 1993, Korea completed the development of its own magnetism only for propulsion, without levitating the vehicle. Such trains have wheels and are not maglevs.*[note 4] Maglev tracks, monorail or not, can also be constructed at grade (i.e. not elevated). Conversely, non-maglev tracks, monorail or not, can be elevated too. Some maglev trains do incorporate wheels and function like linear motor-propelled wheeled vehicles at slower speeds but “take off”and levitate at higher speeds.*[note 5]

Korea's Incheon Airport Maglev, the world's second commercially operating maglev.*[5]

maglev train, shown off at the Taejŏn Expo '93, which was developed further into a full-fledged maglev capable of travelling up to 110 km/h in 2006. This final model was incorporated in the Incheon Airport Maglev which opened in February 3, 2016, making Korea the world's second country to operate its own self-developed maglev after Japan's Linimo.*[25] Compared to Linimo, it has MLX01 Maglev train Superconducting magnet Bogie a more futuristic design thanks to it being lighter with construction costs cut to half.*[26] It links Incheon In- The two notable types of maglev technology are: ternational Airport to the Yongyu Station and Leisure Complex while crossing Yeongjong island.*[27] It offers • Electromagnetic suspension (EMS), electronically 24 CHAPTER 5. MAGLEV

controlled electromagnets in the train attract it to a The major advantage to suspended maglev systems is that magnetically conductive (usually steel) track. they work at all speeds, unlike electrodynamic systems, which only work at a minimum speed of about 30 km/h • Electrodynamic suspension (EDS) uses supercon- (19 mph). This eliminates the need for a separate low- ducting electromagnets or strong permanent mag- speed suspension system, and can simplify track layout. nets that create a magnetic field, which induces cur- On the downside, the dynamic instability demands fine rents in nearby metallic conductors when there is rel- track tolerances, which can offset this advantage. Eric ative movement, which pushes and pulls the train to- Laithwaite was concerned that to meet required toler- wards the designed levitation position on the guide ances, the gap between magnets and rail would have to way. be increased to the point where the magnets would be un- reasonably large.*[39] In practice, this problem was ad- Another technology, which was designed, proven mathe- dressed through improved feedback systems, which sup- matically, peer-reviewed, and patented, but is, as of May port the required tolerances. 2015, unbuilt, is magnetodynamic suspension (MDS). It uses the attractive magnetic force of a permanent magnet array near a steel track to lift the train and hold it in place. 5.3.2 Electrodynamic suspension (EDS) Other technologies such as repulsive permanent magnets and superconducting magnets have seen some research. Main article: Electrodynamic suspension In electrodynamic suspension (EDS), both the guide-

5.3.1 Electromagnetic suspension

Main article: Electromagnetic suspension In electromagnetic suspension (EMS) systems, the train

The Japanese SCMaglev's EDS suspension is powered by the magnetic ﬁelds induced either side of the vehicle by the passage of the vehicle's superconducting magnets.

S SN SN N

SN Electromagnetic suspension (EMS) is used to levitate the Transrapid on the track, so that the train can be faster than NS wheeled mass transit systems*[35]*[36]

N NS NS S levitates above a steel rail while electromagnets, attached to the train, are oriented toward the rail from below. The EDS Maglev propulsion via propulsion coils system is typically arranged on a series of C-shaped arms, with the upper portion of the arm attached to the vehicle, way and the train exert a magnetic field, and the train and the lower inside edge containing the magnets. The is levitated by the repulsive and attractive force between rail is situated inside the C, between the upper and lower these magnetic fields.*[40] In some configurations, the edges. train can be levitated only by repulsive force. In the early Magnetic attraction varies inversely with the cube of dis- stages of maglev development at the Miyazaki test track, tance, so minor changes in distance between the mag- a purely repulsive system was used instead of the later nets and the rail produce greatly varying forces. These repulsive and attractive EDS system.*[41] The magnetic changes in force are dynamically unstable – a slight diver- field is produced either by superconducting magnets (as gence from the optimum position tends to grow, requir- in JR–Maglev) or by an array of permanent magnets (as ing sophisticated feedback systems to maintain a constant in Inductrack). The repulsive and attractive force in the distance from the track, (approximately 15 millimetres track is created by an induced magnetic field in wires or (0.59 in)).*[37]*[38] other conducting strips in the track. A major advantage 5.3. TECHNOLOGY 25 of EDS maglev systems is that they are dynamically stable 5.3.4 Evaluation – changes in distance between the track and the magnets creates strong forces to return the system to its original Each implementation of the magnetic levitation princi- position.*[39] In addition, the attractive force varies in ple for train-type travel involves advantages and disad- the opposite manner, providing the same adjustment ef- vantages. fects. No active feedback control is needed. Neither Inductrack nor the Superconducting EDS are able However, at slow speeds, the current induced in these to levitate vehicles at a standstill, although Inductrack coils and the resultant magnetic flux is not large enough provides levitation at much lower speed; wheels are re- to levitate the train. For this reason, the train must have quired for these systems. EMS systems are wheel-free. wheels or some other form of landing gear to support the The German Transrapid, Japanese HSST (Linimo), and train until it reaches take-off speed. Since a train may Korean Rotem EMS maglevs levitate at a standstill, with stop at any location, due to equipment problems for in- electricity extracted from guideway using power rails for stance, the entire track must be able to support both low- the latter two, and wirelessly for Transrapid. If guideway and high-speed operation. power is lost on the move, the Transrapid is still able to Another downside is that the EDS system naturally cre- generate levitation down to 10 km/h (6.2 mph) speed, us- ates a field in the track in front and to the rear of the lift ing the power from onboard batteries. This is not the case magnets, which acts against the magnets and creates mag- with the HSST and Rotem systems. netic drag. This is generally only a concern at low speeds (This is one of the reasons why JR abandoned a purely repulsive system and adopted the sidewall levitation sys- Propulsion tem.)*[41] At higher speeds other modes of drag domi- nate.*[39] EMS systems such as HSST/Linimo can provide both levitation and propulsion using an onboard linear motor. But The drag force can be used to the electrodynamic sys- EDS systems and some EMS systems such as Transrapid tem's advantage, however, as it creates a varying force levitate but do not propel. Such systems need some other in the rails that can be used as a reactionary system to technology for propulsion. A linear motor (propulsion drive the train, without the need for a separate reaction coils) mounted in the track is one solution. Over long plate, as in most linear motor systems. Laithwaite led distances coil costs could be prohibitive. development of such “traverse-flux”systems at his Im- perial College laboratory.*[39] Alternatively, propulsion coils on the guideway are used to exert a force on the Stability magnets in the train and make the train move forward. The propulsion coils that exert a force on the train are Earnshaw's theorem shows that no combination of static effectively a linear motor: an alternating current through magnets can be in a stable equilibrium.*[48] Therefore the coils generates a continuously varying magnetic field a dynamic (time varying) magnetic field is required to that moves forward along the track. The frequency of the achieve stabilization. EMS systems rely on active elec- alternating current is synchronized to match the speed of tronic stabilization that constantly measures the bearing the train. The offset between the field exerted by magnets distance and adjusts the electromagnet current accord- on the train and the applied field creates a force moving ingly. EDS systems rely on changing magnetic fields to the train forward. create currents, which can give passive stability. Because maglev vehicles essentially fly, stabilisation of pitch, roll and yaw is required. In addition to rotation, surge (forward and backward motions), sway (sideways 5.3.3 Tracks motion) or heave (up and down motions) can be prob- lematic. “ ” The term maglev refers not only to the vehicles, but Superconducting magnets on a train above a track made to the railway system as well, specifically designed for out of a permanent magnet lock the train into its lateral magnetic levitation and propulsion. All operational im- position. It can move linearly along the track, but not plementations of maglev technology make minimal use off the track. This is due to the Meissner effect and flux of wheeled train technology and are not compatible with pinning. conventional rail tracks. Because they cannot share existing infrastructure, maglev systems must be designed as standalone systems. The SPM maglev system is inter- Guidance system operable with steel rail tracks and would permit maglev vehicles and conventional trains to operate on the same Some systems use Null Current systems (also sometimes tracks. MAN in Germany also designed a maglev system called Null Flux systems).*[40]*[49] These use a coil that that worked with conventional rails, but it was never fully is wound so that it enters two opposing, alternating fields, developed.*[39] so that the average flux in the loop is zero. When the 26 CHAPTER 5. MAGLEV vehicle is in the straight ahead position, no current flows, • Maintenance: Maglev trains currently in operation but any moves off-line create flux that generates a field have demonstrated the need for minimal guideway that naturally pushes/pulls it back into line. maintenance. Vehicle maintenance is also minimal (based on hours of operation, rather than on speed or distance traveled). Traditional rail is subject to me- 5.3.5 Evacuated tubes chanical wear and tear that increases exponentially with speed, also increasing maintenance.*[54] Main article: Vactrain • Weather: Maglev trains are little affected by snow, ice, severe cold, rain or high winds. However, they Some systems (notably the Swissmetro system) propose have not operated in the wide range of conditions the use of vactrains̶maglev train technology used in that traditional friction-based rail systems have op- evacuated (airless) tubes, which removes air drag. This erated. Maglev vehicles accelerate and decelerate has the potential to increase speed and efficiency greatly, faster than mechanical systems regardless of the as most of the energy for conventional maglev trains is slickness of the guideway or the slope of the grade * lost to aerodynamic drag. [50] because they are non-contact systems.*[54] One potential risk for passengers of trains operating in evacuated tubes is that they could be exposed to the risk • Track: Maglev trains are not compatible with con- of cabin depressurization unless tunnel safety monitoring ventional track, and therefore require custom infras- systems can repressurize the tube in the event of a train tructure for their entire route. By contrast conven- malfunction or accident though since trains are likely to tional high-speed trains such as the TGV are able to operate at or near the Earth's surface, emergency restora- run, albeit at reduced speeds, on existing rail infras- tion of ambient pressure should be straightforward. The tructure, thus reducing expenditure where new in- RAND Corporation has depicted a vacuum tube train that frastructure would be particularly expensive (such as could, in theory, cross the Atlantic or the USA in ~21 the final approaches to city terminals), or on exten- minutes.*[51] sions where traffic does not justify new infrastructure. John Harding, former chief maglev scientist at the Federal Railroad Administration claimed that 5.3.6 Energy use separate maglev infrastructure more than pays for itself with higher levels of all-weather operational Energy for maglev trains is used to accelerate the train. availability and nominal maintenance costs. These Energy may be regained when the train slows down via claims have yet to be proven in an intense opera- regenerative braking. It also levitates and stabilises the tional setting and does not consider the increased train's movement. Most of the energy is needed to over- maglev construction costs. come "air drag". Some energy is used for air condition- • ing, heating, lighting and other miscellany. Efficiency: Conventional rail is probably more efficient at lower speeds. But due to the lack of phys- At low speeds the percentage of power used for levitation ical contact between the track and the vehicle, ma- can be significant, consuming up to 15% more power than glev trains experience no rolling resistance, leaving * a subway or light rail service. [52] For short distances the only air resistance and electromagnetic drag, poten- energy used for acceleration might be considerable. tially improving power efficiency.*[55] Some sys- The power used to overcome air drag increases with the tems however such as the Central Japan Railway cube of the velocity and hence dominates at high speed. Company SCMaglev use rubber tires at low speeds, The energy needed per unit distance increases by the reducing efficiency gains. square of the velocity and the time decreases linearly. For • example, 2.5 times as much power is needed to travel at Weight: The electromagnets in many EMS and 400 km/h than 300 km/h.*[53] EDS designs require between 1 and 2 kilowatts per ton.*[56] The use of superconductor magnets can reduce the electromagnets' energy consumption. A 5.3.7 Comparison with conventional trains 50-ton Transrapid maglev vehicle can lift an additional 20 tons, for a total of 70 tons, which con- sumes 70-140 kW. Most energy use for the TRI Maglev transport is non-contact and electric powered. It is for propulsion and overcoming air resistance at relies less or not at all on the wheels, bearings and axles speeds over 100 mph. common to wheeled rail systems.*[54] • Weight loading: High speed rail requires more • Speed: Maglev allows higher top speeds than con- support and construction for its concentrated wheel ventional rail, but experimental wheel-based high- loading. Maglev cars are lighter and distribute speed trains have demonstrated similar speeds. weight more evenly.*[57] 5.4. ECONOMICS 27

• Noise: Because the major source of noise of a ma- • Travel time: Maglevs do not face the extended se- glev train comes from displaced air rather than from curity protocols faced by air travelers nor is time wheels touching rails, maglev trains produce less consumed for taxiing, or for queuing for take-off and noise than a conventional train at equivalent speeds. landing. However, the psychoacoustic profile of the maglev may reduce this benefit: a study concluded that maglev noise should be rated like road traffic, while conventional trains experience a 5–10 dB“bonus”, as they are found less annoying at the same loudness 5.4 Economics level.*[58]*[59]*[60] • Braking: Braking and overhead wire wear The Shanghai maglev demonstration line cost US$1.2 bil- * have caused problems for the Fastech 360 rail lion to build. [64] This total includes capital costs such Shinkansen. Maglev would eliminate these issues. as right-of-way clearing, extensive pile driving, on-site guideway manufacturing, in-situ pier construction at 25 • Magnet reliability: At higher temperatures mag- metre intervals, a maintenance facility and vehicle yard, nets may fail. New alloys and manufacturing tech- several switches, two stations, operations and control sys- niques have addressed this issue. tems, power feed system, cables and inverters, and operational training. Ridership is not a primary focus of • Control systems: No signalling systems are needed this demonstration line, since the Longyang Road station for high-speed rail, because such systems are com- is on the eastern outskirts of Shanghai. Once the line is puter controlled. Human operators cannot react fast extended to South Shanghai Train station and Hongqiao enough to manage high-speed trains. High speed Airport station, which may not happen because of eco- systems require dedicated rights of way and are usu- nomic reasons, ridership was expected to cover operation ally elevated. Two maglev system microwave towers and maintenance costs and generate significant net rev- are in constant contact with trains. There is no need enue. for train whistles or horns, either. The South Shanghai extension was expected to cost ap- • Terrain: Maglevs are able to ascend higher grades, proximately US$18 million per kilometre. In 2006 the offering more routing flexibility and reduced tunnel- German government invested $125 million in guideway * ing. [57] cost reduction development that produced an all-concrete modular design that is faster to build and is 30% less 5.3.8 Comparison with aircraft costly. Other new construction techniques were also developed that put maglev at or below price parity with new high-speed rail construction.*[65] Differences between airplane and maglev travel: The United States Federal Railroad Administration, in a • Efficiency: For maglev systems the lift-to-drag ratio 2005 report to Congress, estimated cost per mile of be- * can exceed that of aircraft (for example Inductrack tween $50m and $100m. [66] The Maryland Transit Ad- can approach 200:1 at high speed, far higher than ministration (MTA) Environmental Impact Statement es- any aircraft). This can make maglev more efficient timated a pricetag at US$4.9 billion for construction, and * per kilometer. However, at high cruising speeds, $53 million a year for operations of its project. [67] aerodynamic drag is much larger than lift-induced The proposed Chuo Shinkansen maglev in Japan was es- drag. Jets take advantage of low air density at high timated to cost approximately US$82 billion to build, altitudes to significantly reduce air drag. Hence de- with a route requiring long tunnels. A Tokaido maglev spite their lift-to-drag ratio disadvantage, they can route replacing the current Shinkansen would cost 1/10 travel more efficiently at high speeds than maglev the cost, as no new tunnel would be needed, but noise trains that operate at sea level. pollution issues made this infeasible. • Routing: While aircraft can theoretically take any The only low-speed maglev (100 km/h or 62 mph) cur- route between points, commercial air routes are rently operational, the Japanese Linimo HSST, cost ap- rigidly defined. Maglevs offer competitive journey proximately US$100 million/km to build.*[68] Besides times over distances of 800 kilometres (500 miles) offering improved operation and maintenance costs over or less. Additionally, maglevs can easily serve inter- other transit systems, these low-speed maglevs provide mediate destinations. ultra-high levels of operational reliability and introduce little noiseand generate zero air pollution into dense ur- • Availability: Maglevs are little affected by weather. ban settings. • Safety: Maglevs offer a significant safety margin As more maglev systems are deployed, experts expected since maglevs do not crash into other maglevs or construction costs to drop by employing new construction leave their guideways.*[61]*[62]*[63] methods and from economies of scale.*[69] 28 CHAPTER 5. MAGLEV

5.5 Records FTA's UMTD program

The highest recorded maglev speed is 603 km/h (375 In the US, the Federal Transit Administration (FTA) Ur- mph), achieved in Japan by JR Central's L0 supercon- ban Maglev Technology Demonstration program funded ducting Maglev on 21 April 2015,*[70] 28 km/h (17 the design of several low-speed urban maglev demonstra- mph) faster than the conventional TGV wheel-rail speed tion projects. It assessed HSST for the Maryland De- record. However, the operational and performance dif- partment of Transportation and maglev technology for ferences between these two very diﬀerent technologies is the Colorado Department of Transportation. The FTA far greater. The TGV record was achieved accelerating also funded work by General Atomics at California Uni- down a 72.4 km (45.0 mi) slight decline, requiring 13 versity of Pennsylvania to evaluate the MagneMotion minutes. It then took another 77.25 km (48.00 mi) for M3 and of the Maglev2000 of Florida superconduct- the TGV to stop, requiring a total distance of 149.65 km ing EDS system. Other US urban maglev demonstration (92.99 mi) for the test.*[71] The MLX01 record, how- projects of note are the LEVX in Washington State and ever, was achieved on the 18.4 km (11.4 mi) Yamanashi the Massachusetts-based Magplane. test track – 1/8 the distance.*[72] No maglev or wheel- rail commercial operation has actually been attempted at Southwest Jiaotong University, China speeds over 500 km/h. On 31 December 2000, the ﬁrst crewed high-temperature 5.5.1 History of maglev speed records superconducting maglev was tested successfully at Southwest Jiaotong University, Chengdu, China. This system is based on the principle that bulk high- 5.6 Systems temperature superconductors can be levitated stably above or below a permanent magnet. The load was over 5.6.1 Test tracks 530 kg (1,170 lb) and the levitation gap over 20 mm (0.79 in). The system uses liquid nitrogen to cool the superconductor.*[80]*[81] San Diego, USA

General Atomics has a 120-metre test facility in San 5.6.2 Operational systems Diego, that is used to test Union Paciﬁc's 8 km (5.0 mi) freight shuttle in Los Angeles. The technology is “pas- Shanghai Maglev sive”(or “permanent”), using permanent magnets in a halbach array for lift and requiring no electromagnets for either levitation or propulsion. General Atomics received US$90 million in research funding from the federal government. They are also considering their technology for high-speed passenger services.*[75]

SCMaglev, Japan

Main article: SCMaglev

Japan has a demonstration line in Yamanashi prefecture A maglev train coming out of the Pudong International Airport where test train SCMaglev L0 Series Shinkansen reached * 603 km/h (375 mph), faster than any wheeled trains. [70] Main article: Shanghai Maglev Train These trains use superconducting magnets, which allow for a larger gap, and repulsive/attractive-type electrody- * * In January 2001, the Chinese signed an agreement with namic suspension (EDS). [40] [76] In comparison Tran- Transrapid to build an EMS high-speed maglev line to srapid uses conventional electromagnets and attractive- * * link Pudong International Airport with Longyang Road type electromagnetic suspension (EMS). [77] [78] Metro station on the eastern edge of Shanghai. This On 15 November 2014, The Central Japan Railway Com- Shanghai Maglev Train demonstration line, or Initial Op- pany ran eight days of testing for the experimental maglev erating Segment (IOS), has been in commercial opera- Shinkansen train on its test track in Yamanashi Prefec- tions since April 2004*[82] and now operates 115 daily ture. One hundred passengers covered a 42.8 km (27- trips (up from 110 in 2010) that traverse the 30 km (19 mile) route between the cities of Uenohara and Fuefuki, mi) between the two stations in 7 minutes, achieving a reaching speeds of up to 500 km/h (311 mph).*[79] top speed of 431 km/h (268 mph) and averaging 266 5.7. MAGLEVS UNDER CONSTRUCTION 29 km/h (165 mph).*[83] On a 12 November 2003 system commissioning test run, it achieved 501 km/h (311 mph), its designed top cruising speed. The Shanghai maglev is faster than Birmingham technology and comes with on-time – to the second – reliability greater than 99.97%.*[84] Plans to extend the line to Shanghai South Railway Sta- tion and Hongqiao Airport on the western edge of Shang- hai are on hold. After the Shanghai–Hangzhou Passen- ger Railway became operational in late 2010, the maglev extension became somewhat redundant and may be can- celed.

Linimo (Tobu Kyuryo Line, Japan)

Maglev train departing Incheon International Airport Station.

Linimo, with the Incheon Airport Maglev beginning commercial operation in February 3, 2016.*[5] It was developed and built domestically. Compared to Linimo, it has a more futuristic design thanks to it being lighter * Linimo train approaching Banpaku Kinen Koen, towards Fuji- with construction costs cut to half. [26] The country was gaoka Station in March 2005 the third to develop a maglev system (after Germany and Japan). It connects Incheon International Airport with * * Main article: Linimo Yongyu, cutting journey time. [86] [87] The first maglev test trials using electromagnetic suspen- The commercial automated“Urban Maglev”system com- sion opened to public was HML-03, made by Hyundai menced operation in March 2005 in Aichi, Japan. The Heavy Industries for the Daejeon Expo in 1993, after Tobu-kyuryo Line, otherwise known as the Linimo line, five years of research and manufacturing two prototypes, * * * covers 9 km (5.6 mi). It has a minimum operating radius HML-01 and HML-02. [88] [89] [90] Government re- of 75 m (246 ft) and a maximum gradient of 6%. The search on urban maglev using electromagnetic suspension * linear-motor magnetically levitated train has a top speed began in 1994. [90] The first operating urban maglev was of 100 km/h (62 mph). More than 10 million passengers UTM-02 in Daejeon beginning on 21 April 2008 after used this“urban maglev”line in its first three months of 14 years of development and one prototype; UTM-01. operation. At 100 km/h (62 mph), it is sufficiently fast for The train runs on a 1 km (0.62 mi) track between Expo * * frequent stops, has little or no noise impact on surround- Park and National Science Museum. [91] [92] Mean- ing communities, can navigate short radius rights of way, while UTM-02 conducted the world's first ever maglev * * and operates during inclement weather. The trains were simulation. [93] [94] However UTM-02 is still the sec- designed by the Chubu HSST Development Corporation, ond prototype of a final model. The final UTM model of which also operates a test track in Nagoya.*[85] Rotem's urban maglev, UTM-03, was scheduled to debut at the end of 2014 in Incheon's Yeongjong island where Incheon International Airport is located.*[95] Incheon Airport Maglev

Main article: Incheon Airport Maglev

South Korea is the second country in the world to suc- 5.7 Maglevs under construction ceed in commercializing maglev technology after Japan's 30 CHAPTER 5. MAGLEV

5.7.1 AMT test track – Powder Springs, plan for the Chuo Shinkansen bullet train system was ﬁ- Georgia nalized based on the Law for Construction of Country- wide Shinkansen. The Linear Chuo Shinkansen Project A second prototype system in Powder Springs, Georgia, aimed to operate the Superconductive Magnetically Lev- USA, was built by American Maglev Technology, Inc. itated Train to connect Tokyo and Osaka by way of The test track is 610 m (2,000 feet) long with a 168.6 m Nagoya, the capital city of Aichi, in approximately one * (550 feet) curve. Vehicles are operated up to 60 km/h hour at a speed of 500 km/h (310 mph). [101] The full (37 mph), below the proposed operational maximum of track between Tokyo and Osaka was to be completed in * * 97 km/h (60 mph). A June 2013 review of the technology 2045. [102] [103] called for an extensive testing program to be carried out L0 Series train type undergoing testing by the Central to ensure the system complies with various regulatory re- Japan Railway Company (JR Central) for eventual use on quirements including the American Society of Civil Engi- the Chūō Shinkansen line set a world speed record of 603 neers (ASCE) People Mover Standard. The review noted km/h (375 mph) on 21 April 2015.*[70] The trains are that the test track is too short to assess the vehicles' dy- planned to run at a maximum speed of 505 km/h (314 * namics at the maximum proposed speeds. [96] mph),*[104] oﬀering journey times of 40 minutes between Tokyo (Shinagawa Station) and Nagoya, and 1 hour 7 minutes between Tokyo and Osaka.*[105] 5.7.2 Beijing S1 line

Main article: Line S1, BCR 5.7.5 SkyTran – Tel Aviv (Israel)

Skytran announced it would build an elevated network The Beijing municipal government is building China's of sky cars in Tel Aviv, Israel. The technology was de- first low-speed maglev line, the Line S1, BCR, using tech- veloped by NASA with the support of Israel Aerospace nology developed by Defense Technology University. It Industries.*[106] The system was meant to be suspended is a 10.2 km (6.3 mi) long S1-West commuter rail line, from an elevated track. The vehicles would travel at 70 which, together with seven other conventional lines, be- km/h (43 mph) although the commercial rollout was ex- gan construction on 28 February 2011. The top speed pected to offer much faster vehicles. A trial of the sys- will be 105 km/h (65 mph). This project was scheduled tem was to be built with a test track on the campus of to be completed in 2015.*[97] Israel Aerospace Industries. Once successful, a full commercial version of SkyTran was expected to be rolled out first in Tel Aviv.*[107] The trial was scheduled to be up 5.7.3 Changsha Maglev and running by the end of 2015.*[108]*[109] The company stated that speeds of up to 240 km/h (150 mph) are Main article: Changsha Maglev achievable.*[110]

The Hunan provincial government launched the construction of a maglev line between Changsha Huanghua In- 5.8 Proposed maglev systems ternational Airport and Changsha South Railway Station. Construction started in May 2014, to be completed by the Main article: List of maglev train proposals end of 2015.*[98]*[99]

Many maglev systems have been proposed in North 5.7.4 Tokyo – Nagoya – Osaka America, Asia and Europe.*[111] Many are in the early planning stages or were explicitly rejected. Main article: Chūō Shinkansen Construction of Chuo Shinkansen began in 2014. It 5.8.1 Australia

Sydney-Canberra

A High Speed Rail link between Sydney and Canberra was proposed by Federal Member for Eden-Monaro Peter Hendy*[112] in early 2015. Hendy argued that the project would have major implications for developing re- The Chūō Shinkansen route (bold yellow and red line) and exist- gional Australia – particularly the south east corner of ing Tōkaidō Shinkansen route (thin blue line) New South Wales.*[112]

was expected to begin operations by 2027.*[100] The Sydney-Illawarra 5.8. PROPOSED MAGLEV SYSTEMS 31

A maglev route was proposed between Sydney and speed connection between Malpensa airport to the cities Wollongong.*[113] The proposal came to prominence in of Milan, Bergamo and Brescia.*[116] the mid-1990s. The Sydney–Wollongong commuter cor- On March 2011 Nicola Oliva proposed a maglev con- ridor is the largest in Australia, with upwards of 20,000 nection between Pisa airport and the cities of Prato and people commuting each day. Current trains use the Florence (Santa Maria Novella train station and Florence Illawarra line, between the cliﬀ face of the Illawarra es- Airport).*[117]*[118] The travelling time would be re- carpment and the Paciﬁc Ocean, with travel times about duced from the typical hour and a quarter to around two hours. The proposal would cut travel times to 20 min- twenty minutes.*[119] The second part of the line would utes. be a connection to Livorno, to integrate maritime, aerial and terrestrial transport systems.*[120]*[121] Melbourne 5.8.3 United Kingdom

Main article: UK Ultraspeed

London – Glasgow: A line*[122] was proposed in the United Kingdom from London to Glasgow with several route options through the Midlands, Northwest and Northeast of England. It was reported to be under favourable consideration by the government.*[123] The approach was rejected in the Government White Paper Delivering a Sustainable Railway published on 24 July 2007.*[124] Another high-speed link was planned between Glasgow and Edinburgh but the technology re- mained unsettled.*[125]*[126]*[127]

5.8.4 United States

Union Pacific freight conveyor: Plans are under way by American rail road operator Union Pacific to build a 7.9 The proposed Melbourne maglev connecting the city of Geelong km (4.9 mi) container shuttle between the ports of Los through Metropolitan Melbourne's outer suburban growth corri- Angeles and Long Beach, with UP's intermodal container dors, Tullamarine and Avalon domestic in and international ter- transfer facility. The system would be based on“passive” minals in under 20 mins and on to Frankston, Victoria, in under technology, especially well suited to freight transfer as no 30 minutes power is needed on board. The vehicle is a chassis that glides to its destination. The system is being designed by In late 2008, a proposal was put forward to the General Atomics.*[75] Government of Victoria to build a privately funded and operated maglev line to service the Greater Melbourne California-Nevada Interstate Maglev: High-speed ma- metropolitan area in response to the Eddington Transport glev lines between major cities of southern California and Report that did not investigate above-ground transport Las Vegas are under study via the California-Nevada In- * options.*[114]*[115] The maglev would service a pop- terstate Maglev Project. [128] This plan was originally ulation of over 4 million and the proposal was costed at proposed as part of an I-5 or I-15 expansion plan, but the A$8 billion. federal government ruled that it must be separated from interstate public work projects. However despite road congestion and Australia's highest roadspace per capita, the government dismissed the pro- After the decision, private groups from Nevada proposed posal in favour of road expansion including an A$8.5 bil- a line running from Las Vegas to Los Angeles with stops lion road tunnel, $6 billion extension of the Eastlink to in Primm, Nevada; Baker, California; and other points the Western Ring Road and a $700 million Frankston By- throughout San Bernardino County into Los Angeles. pass. Politicians expressed concern that a high-speed rail line out of state would carry spending out of state along with travelers. 5.8.2 Italy Baltimore – Washington D.C. Maglev: A 64 km (40 mi) project has been proposed linking Camden A first proposal was formalized on April 2008, in Brescia, Yards in Baltimore and Baltimore-Washington Interna- by journalist Andrew Spannaus who recommended a high tional (BWI) Airport to Union Station in Washington, 32 CHAPTER 5. MAGLEV

D.C.*[129] 5.8.7 Switzerland The Pennsylvania Project: The Pennsylvania High- Speed Maglev Project corridor extends from the SwissRapide: The SwissRapide AG together with the Pittsburgh International Airport to Greensburg, with SwissRapide Consortium was planning and developing intermediate stops in Downtown Pittsburgh and the first maglev monorail system for intercity traffic the Monroeville. This initial project was claimed to serve country's between major cities. SwissRapide was to be approximately 2.4 million people in the Pittsburgh financed by private investors. In the long-term, the Swis- metropolitan area. The Baltimore proposal competed sRapide Express was to connect the major cities north with the Pittsburgh proposal for a US$90 million federal of the Alps between Geneva and St. Gallen, including grant.*[130] Lucerne and Basel. The first projects were Bern – Zurich, Lausanne – Geneva as well as Zurich – Winterthur. The San Diego-Imperial County airport: In 2006 San first line (Lausanne – Geneva or Zurich – Winterthur) Diego commissioned a study for a maglev line to a pro- could go into service as early as 2020.*[139]*[140] posed airport located in Imperial County. SANDAG claimed that the concept would be an“airports [sic] with- Swissmetro: An earlier project, Swissmetro AG en- out terminals”, allowing passengers to check in at a termi- visioned a partially evacuated underground maglev (a nal in San Diego (“satellite terminals”), take the train vactrain). As with SwissRapide, Swissmetro envisioned to the airport and directly board the airplane. In addi- connecting the major cities in Switzerland with one an- tion, the train would have the potential to carry freight. other. In 2011, Swissmetro AG was dissolved and the Further studies were requested although no funding was IPRs from the organisation were passed onto the EPFL agreed.*[131] in Lausanne.*[141] Orlando International Airport to Orange County Convention Center: In December 2012 the Florida De- partment of Transportation gave conditional approval to a proposal by American Maglev to build a privately run 5.8.8 China 14.9-mile (24.0 km), 5-station line from Orlando Inter- national Airport to Orange County Convention Center. Shanghai – Hangzhou The Department requested a technical assessment and China planned to extend the existing Shanghai Maglev said there would be a request for proposals issued to re- Train,*[142] initially by some 35 kilometres to Shanghai veal any competing plans. The route requires the use of Hongqiao Airport and then 200 kilometres to the city of a public right of way.*[132] If the first phase succeeded Hangzhou (Shanghai-Hangzhou Maglev Train). If built, American Maglev would propose two further phases (of this would be the first inter-city maglev rail line in com- 4.9 and 19.4 miles (7.9 and 31.2 km)) to carry the line to mercial service. Walt Disney World.*[133] The project was controversial and repeatedly delayed. In May 2007 the project was suspended by officials, report- 5.8.5 Puerto Rico edly due to public concerns about radiation from the system.*[143] In January and February 2008 hundreds of residents demonstrated in downtown Shanghai that the San Juan – Caguas: A 16.7-mile (26.8 km) maglev line route came too close to their homes, citing concerns project was proposed linking Tren Urbano's Cupey Sta- about sickness due to exposure to the strong magnetic tion in San Juan with two proposed stations in the city field, noise, pollution and devaluation of property near to of Caguas, south of San Juan. The maglev line would run the lines.*[144]*[145] Final approval to build the line was along Highway PR-52, connecting both cities. According granted on 18 August 2008. Originally scheduled to be to American Maglev project cost would be approximately ready by Expo 2010,*[146] plans called for completion US$380 million.*[134]*[135]*[136] by 2014. The Shanghai municipal government considered multiple options, including undergrounding the line 5.8.6 Germany to allay public fears. This same report stated that the final decision had to be approved by the National Development * On 25 September 2007, Bavaria announced a high- and Reform Commission. [147] speed maglev-rail service from Munich to its airport. In 2007 the Shanghai municipal government was consid- The Bavarian government signed contracts with Deutsche ering build a factory in Nanhui district to produce low- Bahn and Transrapid with Siemens and ThyssenKrupp for speed maglev trains for urban use.*[148] * the €1.85 billion project. [137] Shanghai – Beijing On 27 March 2008, the German Transport minister an- A proposed line would have connected Shanghai to Bei- nounced the project had been cancelled due to rising costs jing, over a distance of 1,300 kilometres (800 mi), at an associated with constructing the track. A new estimate estimated cost of £15.5bn.*[149] No projects had been put the project between €3.2–3.4 billion.*[138] revealed as of 2014.*[150] 5.9. INCIDENTS 33

5.8.9 India these suburbs to the city, transit times would be reduced by 70% or more compared to peak hours, and between Mumbai – Delhi Tien Mou and YangMingShan, from approx 20 minutes, A project was presented to Indian railway minister to 3 minutes. Key to the line is YangMingShan Station, at (Mamta Banerjee) by an American company to connect ʻTaipei levelʼin the mountain, 200M below YangMing- Mumbai and Delhi. Then Prime Minister Manmohan Shan (YangMing Mountain) Village, with 40 second high Singh said that if the line project was successful the In- speed elevators to the Village. dian government would build lines between other cities Linimo or a similar system would be preferred, as being and also between Mumbai Central and Chhatrapati Shiv- the core of Taipei's public transport system, it should run aji International Airport.*[151] 24 hours a day. Also, in certain areas it would run within Mumbai – Nagpur metres of apartments, so the near silent operation, and The State of Maharashtra approved a feasibility study for minimal maintenance requirements of maglev would be a maglev train between Mumbai and Nagpur, some 1,000 major advantages. km (620 mi) apart.*[152] Chennai – Bangalore – Mysore An extension of the line could run to Chiang Kai Shek A detailed report was to be prepared and submitted by Airport, and possibly on down the island, passing through December 2012 for a line to connect Chennai to Mysore major population centres, which the High Speed Rail via Bangalore at a cost $26 million per kilometre, reach- must avoid. The minimal vibration of maglev would ing speeds of 350 km/h.*[153] also be suitable to provide access Hsinchu Science Park, where sensitive silicon foundries are located. In the other direction, connection to the Tansui Line and to High 5.8.10 Malaysia Speed ferries at Tansui would provide overnight travel to Shanghai and Nagasaki, and to Busan or Mokpo in South A Consortium led by UEM Group Bhd and ARA Group, Korea, thus interconnecting the public transport systems proposed Maglev technology to link Malaysian cities to of four countries, with great savings in fossil fuel con- Singapore. The idea was ﬁrst mooted by YTL Group. Its sumption compared to ﬂight. technology partner then was said to be Siemens. High YangMingShan MRT Line won the 'Engineering Excel- costs sank the proposal. The concept of a high-speed rail lence' Award, at the 2013 World Metro Summit in Shang- link from Kuala Lumpur to Singapore resurfaced. It was hai. cited as a proposed“high impact”project in the Economic Transformation Programme (ETP) that was unveiled in 2010.*[154] 5.8.13 Hong Kong

Main article: Guangzhou–Shenzhen–Hong Kong Ex- 5.8.11 Iran press Rail Link In May 2009, Iran and a German company signed an agreement to use maglev to link Tehran and Mashhad. The Express Rail Link, previously known as the Regional The agreement was signed at the Mashhad International Express, which will connect Kowloon with the territory's Fair site between Iranian Ministry of Roads and Trans- border with China, explored different technologies and portation and the German company. The 900 km (560 designs in its planning stage, between Maglev and con- mi) line allegedly could reduce travel time between ventional highspeed railway, and if the latter was chosen, Tehran and Mashhad to about 2.5 hours.*[155] Munich- between a dedicated new route and sharing the tracks with based Schlegel Consulting Engineers said they had signed the existing West Rail. Finally conventional highspeed the contract with the Iranian ministry of transport and with dedicated new route was chosen. It is expected to the governor of Mashad. “We have been mandated to be operational in 2017. lead a German consortium in this project,”a spokesman said.“We are in a preparatory phase.”The project could be worth between 10 billion and 12 billion euros, the 5.9 Incidents Schlegel spokesman said.*[156] Two incidents involved fires. A Japanese test train in 5.8.12 Taiwan Miyazaki, MLU002, was completely consumed in a fire in 1991.*[157] Low speed maglev (urban maglev) is proposed for Yang- On 11 August 2006, a fire broke out on the commer- MingShan MRT Line for Taipei, a circular line connect- cial Shanghai Transrapid shortly after arriving at the ing Taipei City to New Taipei City, and almost all other Longyang terminal. People were evacuated without in- Taipei transport routes, but especially the access starved cident before the vehicle was moved about 1 kilometre northern suburbs of Tien Mou and YangMingShan. From to keep smoke from filling the station. NAMTI officials 34 CHAPTER 5. MAGLEV toured the SMT maintenance facility in November 2010 [4] This is the case with the Moscow Monorail – currently the and learned that the cause of the fire was "thermal run- only non-maglev linear motor-propelled monorail train in away" in a battery tray. As a result, SMT secured a new active service. battery vendor, installed new temperature sensors and in- [5] This is typically the case with electrodynamic suspension sulators and redesigned the trays. maglev trains. Aerodynamic factors may also play a role On 22 September 2006, a Transrapid train collided with in the levitation of such trains. Where that is the case, a maintenance vehicle on a test/publicity run in Lathen it might be argued that they are technically hybrid sys- (Lower Saxony / north-western Germany).*[158]*[159] tems insofar as their levitation isn't purely magnetic – but Twenty-three people were killed and ten were injured; their linear motors are electromagnetic systems, and these achieve the higher speeds at which the aerodynamic fac- these were the first maglev crash fatalities. The acci- tors come into play. dent was caused by human error. Charges were brought against three Transrapid employees after a year-long in- * vestigation. [160] 5.12 References

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[115] “Melbourne Concepts – Maglev's relevance”. Windana [138] Heller, Gernot (27 March 2008). “Germany scraps Mu- Research. Retrieved 7 September 2009. nich Transrapid as cost spirals”. Reuters. 38 CHAPTER 5. MAGLEV

[139] “Lausanne en 10 minutes” (PDF) (in French). GHI. 3 5.13 Further reading March 2011. Retrieved 20 May 2011. • Heller, Arnie (June 1998). “A New Approach [140] “In 20 Minuten von Zürich nach Bern” (PDF) (in Ger- man). Neue Zürcher Zeitung. 20 June 2009. Retrieved for Magnetically Levitating Trains̶and Rockets” 20 May 2011. . Science & Technology Review. • [141] “Swissmetro.ch”. Swissmetro.ch. Retrieved 29 Septem- Henry H. Kolm; Richard D. Thornton (October ber 2011. 1973). “Electromagnetic Flight”. Scientiﬁc Amer- ican (Springer Nature) 229 (4): 17–25. [142] McGrath, Dermot (20 January 2003). “China Awaits • High-Speed 'Maglev'". Wired. Hood, Christopher P. (2006). Shinkansen – From Bullet Train to Symbol of Modern Japan. Routledge. [143] “China maglev project suspended amid radiation con- ISBN 0-415-32052-6. cerns”. Xinhua. 26 May 2007. • Moon, Francis C. (1994). Superconducting Levita- [144] “Hundreds protest Shanghai maglev rail extension”. tion Applications to Bearings and Magnetic Trans- Reuters. 12 January 2008. portation. Wiley-VCH. ISBN 0-471-55925-3. [145] Kurtenbach, Elaine (14 January 2008). “Shanghai Resi- • Rossberg, Ralf Roman (1983). Radlos in die dents Protest Maglev Train”. Fox News. Archived from Zukunft? Die Entwicklung neuer Bahnsysteme. Orell the original on 13 September 2009. Füssli Verlag. ASIN B002ROWD5M. [146] “Maglev railway to link Hangzhou, Shanghai”. Xinhua. • Rossberg, Ralf Roman (1993). Radlos in die 6 April 2006. Zukunft? Die Entwicklung neuer Bahnsysteme. Orell [147] “Maglev ﬁnally given approval”. Shanghai Daily. 18 Fuessli Verlag. ISBN 978-3-280-01503-2. August 2008. • Simmons, Jack; Biddle, Gordon (1997). The Oxford Companion to British Railway History: From 1603 [148] “Green light for maglev factory”. Shanghai Daily. 22 November 2007. to the 1990s. Oxford: Oxford University Press. p. 303. ISBN 0-19-211697-5. [149]“China claims train blue riband”. Retrieved 27 December 2014.

[150] “Shanghai welcomes high speed train”. Cnn business. 5.14 External links Retrieved 27 December 2014. • Maglev2000 [151] “Mumbai to Delhi: 3 hours by train”. Express India. 14 June 2005. • North American Maglev Transport Institute

[152] “6 routes identiﬁed for MagLev”. Times of India (India). • International Maglev Charter & Petition 22 June 2007. • Urban Maglev [153] “Bullet train may connect Mysore-Bangalore in 1hr 30 • Windana Research mins Photos”. Yahoo! India Finance. 20 April 2012. Retrieved 2012-11-04. • United States Federal Railroad Administration

[154] “At what cost high-speed rail”. thesundaily.my. • US MagneticGlide • [155] “No Operation”. Presstv.ir. Retrieved 29 September The International Maglev Board Maglev profes- 2011. sional's info plattform for all maglev transport systems and related technologies. [156] “UPDATE 2-ThyssenKrupp, Siemens unaware of Iran train deal”. News.alibaba.com. 30 May 2009. Retrieved • Applied Levitation 29 September 2011. • Fastransit [157] Vranich, Joseph (1 May 1992). “High speed hopes soar” • Maglev Net – Maglev News & Information . Railway Age. • Transrapid [158] “Several Dead in Transrapid Accident”. Speigel Online. 22 September 2006. • The UK Ultraspeed Project • [159] “23 dead in German maglev train accident”. M&C Eu- Japanese Railway Technical Research Institute rope. 22 September 2006. (RTRI) • [160] “German prosecutor charges three Transrapid employees Magnetic Levitation at DMOZ over year-old disaster”. AFX News. 30 September 2007. • Magnetic Levitation for Transportation Archived from the original on 4 June 2011. Chapter 6

Nanotechnology

For the materials science journal, see Nanotechnology On the other hand, nanotechnology raises many of the (journal). same issues as any new technology, including concerns about the toxicity and environmental impact of nano- * Nanotechnology ("nanotech") is manipulation of mat- materials, [5] and their potential effects on global economics, as well as speculation about various doomsday ter on an atomic, molecular, and supramolecular scale. The earliest, widespread description of nanotechnol- scenarios. These concerns have led to a debate among advocacy groups and governments on whether special ogy*[1]*[2] referred to the particular technological goal of precisely manipulating atoms and molecules for fab- regulation of nanotechnology is warranted. rication of macroscale products, also now referred to as molecular nanotechnology. A more generalized description of nanotechnology was subsequently established 6.1 Origins by the National Nanotechnology Initiative, which defines nanotechnology as the manipulation of matter with at Main article: History of nanotechnology least one dimension sized from 1 to 100 nanometers. This definition reflects the fact that quantum mechanical effects are important at this quantum-realm scale, and so The concepts that seeded nanotechnology were first dis- the definition shifted from a particular technological goal cussed in 1959 by renowned physicist Richard Feynman to a research category inclusive of all types of research in his talk There's Plenty of Room at the Bottom, in which and technologies that deal with the special properties of he described the possibility of synthesis via direct ma- matter that occur below the given size threshold. It is nipulation of atoms. The term “nano-technology”was therefore common to see the plural form“nanotechnolo- first used by Norio Taniguchi in 1974, though it was not gies”as well as“nanoscale technologies”to refer to the widely known. broad range of research and applications whose common trait is size. Because of the variety of potential applications (including industrial and military), governments have invested billions of dollars in nanotechnology research. Until 2012, through its National Nanotechnology Initiative, the USA has invested 3.7 billion dollars, the European Union has invested 1.2 billion and Japan 750 million dollars.*[3] Nanotechnology as defined by size is naturally very broad, including fields of science as diverse as surface science, organic chemistry, molecular biology, semiconductor physics, microfabrication, etc.*[4] The associated research and applications are equally diverse, ranging from extensions of conventional device physics to completely new approaches based upon molecular self-assembly, from developing new materials with dimensions on the nanoscale to direct control of matter on the atomic scale. Scientists currently debate the future implications of nan- Comparison of Nanomaterials Sizes otechnology. Nanotechnology may be able to create many new materials and devices with a vast range of Inspired by Feynman's concepts, K. Eric Drexler used the applications, such as in nanomedicine, nanoelectronics, term“nanotechnology”in his 1986 book Engines of Cre- biomaterials energy production, and consumer products. ation: The Coming Era of Nanotechnology, which pro-

39 40 CHAPTER 6. NANOTECHNOLOGY

posed the idea of a nanoscale“assembler”which would political, and commercial attention that led to both con- be able to build a copy of itself and of other items of troversy and progress. Controversies emerged regarding arbitrary complexity with atomic control. Also in 1986, the definitions and potential implications of nanotech- Drexler co-founded The Foresight Institute (with which nologies, exemplified by the Royal Society's report on he is no longer affiliated) to help increase public aware- nanotechnology.*[10] Challenges were raised regarding ness and understanding of nanotechnology concepts and the feasibility of applications envisioned by advocates of implications. molecular nanotechnology, which culminated in a pub- Thus, emergence of nanotechnology as a field in the lic debate between Drexler and Smalley in 2001 and 2003.*[11] 1980s occurred through convergence of Drexler's theoretical and public work, which developed and pop- Meanwhile, commercialization of products based on ularized a conceptual framework for nanotechnology, advancements in nanoscale technologies began emerg- and high-visibility experimental advances that drew ad- ing. These products are limited to bulk applications of ditional wide-scale attention to the prospects of atomic nanomaterials and do not involve atomic control of mat- control of matter. In the 1980s, two major breakthroughs ter. Some examples include the Silver Nano platform sparked the growth of nanotechnology in modern era. for using silver nanoparticles as an antibacterial agent, First, the invention of the scanning tunneling microscope nanoparticle-based transparent sunscreens, carbon fiber strengthening using silica nanoparticles, and carbon nan- in 1981 which provided unprecedented visualization of * * individual atoms and bonds, and was successfully used otubes for stain-resistant textiles. [12] [13] to manipulate individual atoms in 1989. The micro- Governments moved to promote and fund research into scope's developers Gerd Binnig and Heinrich Rohrer at nanotechnology, such as in the U.S. with the National IBM Zurich Research Laboratory received a Nobel Prize Nanotechnology Initiative, which formalized a size-based in Physics in 1986.*[6]*[7] Binnig, Quate and Gerber definition of nanotechnology and established funding for also invented the analogous atomic force microscope that research on the nanoscale, and in Europe via the Euro- year. pean Framework Programmes for Research and Techno- logical Development. By the mid-2000s new and serious scientific attention began to flourish. Projects emerged to produce nanotechnology roadmaps*[14]*[15] which center on atomically precise manipulation of matter and discuss existing and projected capabilities, goals, and applications.

6.2 Fundamental concepts

Nanotechnology is the engineering of functional systems at the molecular scale. This covers both current work and concepts that are more advanced. In its original sense, nanotechnology refers to the projected ability to construct items from the bottom up, using techniques and tools being developed today to make complete, high performance products. One nanometer (nm) is one billionth, or 10*−9, of a me- Buckminsterfullerene C60, also known as the buckyball, is a rep- ter. By comparison, typical carbon-carbon bond lengths, resentative member of the carbon structures known as fullerenes. or the spacing between these atoms in a molecule, are in Members of the fullerene family are a major subject of research falling under the nanotechnology umbrella. the range 0.12–0.15 nm, and a DNA double-helix has a diameter around 2 nm. On the other hand, the smallest cellular life-forms, the bacteria of the genus Mycoplasma, Second, Fullerenes were discovered in 1985 by Harry are around 200 nm in length. By convention, nanotech- Kroto, Richard Smalley, and Robert Curl, who together * * nology is taken as the scale range 1 to 100 nm follow- won the 1996 Nobel Prize in Chemistry. [8] [9] C60 was ing the definition used by the National Nanotechnology not initially described as nanotechnology; the term was Initiative in the US. The lower limit is set by the size of used regarding subsequent work with related graphene atoms (hydrogen has the smallest atoms, which are ap- tubes (called carbon nanotubes and sometimes called proximately a quarter of a nm diameter) since nanotech- Bucky tubes) which suggested potential applications for nology must build its devices from atoms and molecules. nanoscale electronics and devices. The upper limit is more or less arbitrary but is around the In the early 2000s, the field garnered increased scientific, size that phenomena not observed in larger structures start 6.2. FUNDAMENTAL CONCEPTS 41

to become apparent and can be made use of in the nano can become significant when the nanometer size range is device.*[16] These new phenomena make nanotechnol- reached, typically at distances of 100 nanometers or less, ogy distinct from devices which are merely miniaturised the so-called quantum realm. Additionally, a number of versions of an equivalent macroscopic device; such de- physical (mechanical, electrical, optical, etc.) properties vices are on a larger scale and come under the description change when compared to macroscopic systems. One ex- of microtechnology.*[17] ample is the increase in surface area to volume ratio alter- To put that scale in another context, the comparative size ing mechanical, thermal and catalytic properties of ma- of a nanometer to a meter is the same as that of a marble terials. Diffusion and reactions at nanoscale, nanostructures materials and nanodevices with fast ion transport are to the size of the earth.*[18] Or another way of putting it: a nanometer is the amount an average man's beard grows generally referred to nanoionics. Mechanical properties of nanosystems are of interest in the nanomechanics re- in the time it takes him to raise the razor to his face.*[18] search. The catalytic activity of nanomaterials also opens Two main approaches are used in nanotechnology. In the potential risks in their interaction with biomaterials. “bottom-up”approach, materials and devices are built from molecular components which assemble themselves Materials reduced to the nanoscale can show differ- chemically by principles of molecular recognition. In the ent properties compared to what they exhibit on a “top-down”approach, nano-objects are constructed from macroscale, enabling unique applications. For instance, larger entities without atomic-level control.*[19] opaque substances can become transparent (copper); stable materials can turn combustible (aluminium); insolu- Areas of physics such as nanoelectronics, nanomechanics, ble materials may become soluble (gold). A material such nanophotonics and nanoionics have evolved during the as gold, which is chemically inert at normal scales, can last few decades to provide a basic scientific foundation serve as a potent chemical catalyst at nanoscales. Much of nanotechnology. of the fascination with nanotechnology stems from these quantum and surface phenomena that matter exhibits at the nanoscale.*[20] 6.2.1 Larger to smaller: a materials perspective 6.2.2 Simple to complex: a molecular perspective

Main article: Molecular self-assembly

Modern synthetic chemistry has reached the point where it is possible to prepare small molecules to almost any structure. These methods are used today to manufacture a wide variety of useful chemicals such as pharmaceuticals or commercial polymers. This ability raises the question of extending this kind of control to the next-larger level, seeking methods to assemble these single molecules into supramolecular assemblies consisting of many molecules arranged in a well defined manner. These approaches utilize the concepts of molecular self- assembly and/or supramolecular chemistry to automatically arrange themselves into some useful conformation through a bottom-up approach. The concept of molecu- Image of reconstruction on a clean Gold(100) surface, as visu- lar recognition is especially important: molecules can be alized using scanning tunneling microscopy. The positions of the designed so that a specific configuration or arrangement individual atoms composing the surface are visible. is favored due to non-covalent intermolecular forces. The Watson–Crick basepairing rules are a direct result of this, Main article: Nanomaterials as is the specificity of an enzyme being targeted to a single substrate, or the specific folding of the protein itself. Several phenomena become pronounced as the size of the Thus, two or more components can be designed to be system decreases. These include statistical mechanical complementary and mutually attractive so that they make effects, as well as quantum mechanical effects, for exam- a more complex and useful whole. ple the“quantum size effect”where the electronic prop- Such bottom-up approaches should be capable of produc- erties of solids are altered with great reductions in particle ing devices in parallel and be much cheaper than top- size. This effect does not come into play by going from down methods, but could potentially be overwhelmed macro to micro dimensions. However, quantum effects as the size and complexity of the desired assembly in- 42 CHAPTER 6. NANOTECHNOLOGY creases. Most useful structures require complex and ther- This led to an exchange of letters in the ACS publication modynamically unlikely arrangements of atoms. Nev- Chemical & Engineering News in 2003.*[24] Though bi- ertheless, there are many examples of self-assembly ology clearly demonstrates that molecular machine sys- based on molecular recognition in biology, most notably tems are possible, non-biological molecular machines are Watson–Crick basepairing and enzyme-substrate interac- today only in their infancy. Leaders in research on non- tions. The challenge for nanotechnology is whether these biological molecular machines are Dr. Alex Zettl and his principles can be used to engineer new constructs in ad- colleagues at Lawrence Berkeley Laboratories and UC dition to natural ones. Berkeley. They have constructed at least three distinct molecular devices whose motion is controlled from the desktop with changing voltage: a nanotube nanomotor, 6.2.3 Molecular nanotechnology: a long- a molecular actuator,*[25] and a nanoelectromechanical term view relaxation oscillator.*[26] See nanotube nanomotor for more examples. Main article: Molecular nanotechnology An experiment indicating that positional molecular assembly is possible was performed by Ho and Lee at Molecular nanotechnology, sometimes called molecu- Cornell University in 1999. They used a scanning tunnel- lar manufacturing, describes engineered nanosystems ing microscope to move an individual carbon monoxide (nanoscale machines) operating on the molecular scale. molecule (CO) to an individual iron atom (Fe) sitting on Molecular nanotechnology is especially associated with a flat silver crystal, and chemically bound the CO to the the molecular assembler, a machine that can produce a Fe by applying a voltage. desired structure or device atom-by-atom using the principles of mechanosynthesis. Manufacturing in the context of productive nanosystems is not related to, and 6.3 Current research should be clearly distinguished from, the conventional technologies used to manufacture nanomaterials such as carbon nanotubes and nanoparticles. When the term “nanotechnology”was independently coined and popularized by Eric Drexler (who at the time was unaware of an earlier usage by Norio Taniguchi) it referred to a future manufacturing technology based on molecular machine systems. The premise was that molecular scale biological analogies of traditional machine components demonstrated molecular machines were possible: by the countless examples found in biology, it is known that sophisticated, stochastically optimised biological machines can be produced. It is hoped that developments in nanotechnology will make possible their construction by some other means, Graphical representation of a rotaxane, useful as a molecular perhaps using biomimetic principles. However, Drexler switch. and other researchers*[21] have proposed that advanced nanotechnology, although perhaps initially implemented by biomimetic means, ultimately could be based on me- 6.3.1 Nanomaterials chanical engineering principles, namely, a manufacturing technology based on the mechanical functionality of The nanomaterials field includes subfields which develop these components (such as gears, bearings, motors, and or study materials having unique properties arising from structural members) that would enable programmable, their nanoscale dimensions.*[29] positional assembly to atomic specification.*[22] The physics and engineering performance of exemplar de- • signs were analyzed in Drexler's book Nanosystems. Interface and colloid science has given rise to many materials which may be useful in nanotechnology, In general it is very difficult to assemble devices on the such as carbon nanotubes and other fullerenes, and atomic scale, as one has to position atoms on other atoms various nanoparticles and nanorods. Nanomaterials of comparable size and stickiness. Another view, put with fast ion transport are related also to nanoionics * forth by Carlo Montemagno, [23] is that future nanosys- and nanoelectronics. tems will be hybrids of silicon technology and biological molecular machines. Richard Smalley argued that • Nanoscale materials can also be used for bulk ap- mechanosynthesis are impossible due to the difficulties plications; most present commercial applications of in mechanically manipulating individual molecules. nanotechnology are of this flavor. 6.3. CURRENT RESEARCH 43

This DNA tetrahedron*[27] is an artiﬁcially designed nanostruc- ture of the type made in the ﬁeld of DNA nanotechnology. Each edge of the tetrahedron is a 20 base pair DNA double helix, and each vertex is a three-arm junction.

This device transfers energy from nano-thin layers of quantum wells to nanocrystals above them, causing the nanocrystals to emit visible light.*[28]

6.3.2 Bottom-up approaches

These seek to arrange smaller components into more complex assemblies.

• DNA nanotechnology utilizes the speciﬁcity of Watson–Crick basepairing to construct well-deﬁned structures out of DNA and other nucleic acids.

Rotating view of C60, one kind of fullerene. • Approaches from the field of “classical”chemical synthesis (Inorganic and organic synthesis) also aim • Progress has been made in using these materials for at designing molecules with well-defined shape (e.g. * medical applications; see Nanomedicine. bis-peptides [31]). • Nanoscale materials such as nanopillars are some- • times used in solar cells which combats the cost of More generally, molecular self-assembly seeks to traditional Silicon solar cells. use concepts of supramolecular chemistry, and molecular recognition in particular, to cause single- • Development of applications incorporating semi- molecule components to automatically arrange conductor nanoparticles to be used in the next gener- themselves into some useful conformation. ation of products, such as display technology, lighting, solar cells and biological imaging; see quantum • dots. Atomic force microscope tips can be used as a nanoscale“write head”to deposit a chemical upon • Recent application of nanomaterials include a range a surface in a desired pattern in a process called dip of biomedical applications, such as tissue engineer- pen nanolithography. This technique fits into the ing, drug delivery, and biosensors.*[30] larger subfield of nanolithography. 44 CHAPTER 6. NANOTECHNOLOGY

6.3.3 Top-down approaches • Bionanotechnology is the use of biomolecules for applications in nanotechnology, including These seek to create smaller devices by using larger ones use of viruses and lipid assemblies.*[35]*[36] to direct their assembly. Nanocellulose is a potential bulk-scale application.

• Many technologies that descended from conven- 6.3.6 Speculative tional solid-state silicon methods for fabricating microprocessors are now capable of creating fea- These subfields seek to anticipate what inventions nan- tures smaller than 100 nm, falling under the defini- otechnology might yield, or attempt to propose an agenda tion of nanotechnology. Giant magnetoresistance- along which inquiry might progress. These often take a based hard drives already on the market fit this de- big-picture view of nanotechnology, with more emphasis * scription, [32] as do atomic layer deposition (ALD) on its societal implications than the details of how such techniques. Peter Grünberg and Albert Fert re- inventions could actually be created. ceived the Nobel Prize in Physics in 2007 for their discovery of Giant magnetoresistance and contribu- • Molecular nanotechnology is a proposed approach tions to the field of spintronics.*[33] which involves manipulating single molecules in finely controlled, deterministic ways. This is more • Solid-state techniques can also be used to cre- theoretical than the other subfields, and many of its ate devices known as nanoelectromechanical proposed techniques are beyond current capabili- systems or NEMS, which are related to ties. microelectromechanical systems or MEMS. • Nanorobotics centers on self-sufficient machines • Focused ion beams can directly remove material, or of some functionality operating at the nanoscale. even deposit material when suitable precursor gasses There are hopes for applying nanorobots in are applied at the same time. For example, this tech- medicine,*[37]*[38]*[39] but it may not be easy nique is used routinely to create sub-100 nm sections to do such a thing because of several drawbacks of material for analysis in Transmission electron mi- of such devices.*[40] Nevertheless, progress on croscopy. innovative materials and methodologies has been demonstrated with some patents granted about new • Atomic force microscope tips can be used as a nanomanufacturing devices for future commercial nanoscale“write head”to deposit a resist, which is applications, which also progressively helps in the then followed by an etching process to remove ma- development towards nanorobots with the use of terial in a top-down method. embedded nanobioelectronics concepts.*[41]*[42] • Productive nanosystems are “systems of nanosystems”which will be complex nanosystems that pro- 6.3.4 Functional approaches duce atomically precise parts for other nanosystems, not necessarily using novel nanoscale-emergent These seek to develop components of a desired function- properties, but well-understood fundamentals of ality without regard to how they might be assembled. manufacturing. Because of the discrete (i.e. atomic) nature of matter and the possibility of ex- • Molecular scale electronics seeks to develop ponential growth, this stage is seen as the basis of molecules with useful electronic properties. These another industrial revolution. Mihail Roco, one of could then be used as single-molecule components the architects of the USA's National Nanotechnol- in a nanoelectronic device.*[34] For an example ogy Initiative, has proposed four states of nanotech- see rotaxane. nology that seem to parallel the technical progress of the Industrial Revolution, progressing from passive • Synthetic chemical methods can also be used to cre- nanostructures to active nanodevices to complex ate synthetic molecular motors, such as in a so- nanomachines and ultimately to productive nanosys- called nanocar. tems.*[43] • Programmable matter seeks to design materials 6.3.5 Biomimetic approaches whose properties can be easily, reversibly and exter- nally controlled though a fusion of information science and materials science. • Bionics or biomimicry seeks to apply biological methods and systems found in nature, to the study • Due to the popularity and media exposure of the and design of engineering systems and modern tech- term nanotechnology, the words picotechnology and nology. Biomineralization is one example of the sys- femtotechnology have been coined in analogy to it, tems studied. although these are only used rarely and informally. 6.4. TOOLS AND TECHNIQUES 45

6.3.7 Dimensionality in nanomaterials Various techniques of nanolithography such as optical lithography, X-ray lithography dip pen nanolithography, Nanomaterials can be classified in 0D, 1D, 2D and 3D electron beam lithography or nanoimprint lithography nanomaterials. The dimensionality play a major role were also developed. Lithography is a top-down fabri- in determining the characteristic of nanomaterials in- cation technique where a bulk material is reduced in size cluding physical, chemical and biological characteris- to nanoscale pattern. tics. With the decrease in dimensionality, an increase Another group of nanotechnological techniques include in surface-to-volume ratio is observed. This indicate those used for fabrication of nanotubes and nanowires, that smaller dimensional nanomaterials have higher sur- those used in semiconductor fabrication such as deep face area compared to 3D nanomaterials. Recently, ultraviolet lithography, electron beam lithography, fo- two dimensional (2D) nanomaterials are extensively in- cused ion beam machining, nanoimprint lithography, vestigated for electronic, biomedical, drug delivery and atomic layer deposition, and molecular vapor deposition, biosensor applications. and further including molecular self-assembly techniques such as those employing di-block copolymers. The pre- cursors of these techniques preceded the nanotech era, 6.4 Tools and techniques and are extensions in the development of scientific advancements rather than techniques which were devised with the sole purpose of creating nanotechnology and which were results of nanotechnology research. The top-down approach anticipates nanodevices that must be built piece by piece in stages, much as manufactured items are made. Scanning probe microscopy is an important technique both for characterization and synthesis of nanomaterials. Atomic force microscopes and scanning tunneling microscopes can be used to look at surfaces and to move atoms around. By designing different tips for these microscopes, they can be used for carving out structures on surfaces and to help guide self- assembling structures. By using, for example, feature- oriented scanning approach, atoms or molecules can be moved around on a surface with scanning probe microscopy techniques.*[44]*[45] At present, it is expensive and time-consuming for mass production but very Typical AFM setup. A microfabricated cantilever with a sharp suitable for laboratory experimentation. tip is deflected by features on a sample surface, much like in a phonograph but on a much smaller scale. A laser beam reflects In contrast, bottom-up techniques build or grow larger off the backside of the cantilever into a set of photodetectors, al- structures atom by atom or molecule by molecule. These lowing the deflection to be measured and assembled into an image techniques include chemical synthesis, self-assembly and of the surface. positional assembly. Dual polarisation interferometry is one tool suitable for characterisation of self assembled There are several important modern developments. The thin films. Another variation of the bottom-up approach atomic force microscope (AFM) and the Scanning Tun- is molecular beam epitaxy or MBE. Researchers at Bell neling Microscope (STM) are two early versions of scan- Telephone Laboratories like John R. Arthur. Alfred Y. ning probes that launched nanotechnology. There are Cho, and Art C. Gossard developed and implemented other types of scanning probe microscopy. Although MBE as a research tool in the late 1960s and 1970s. conceptually similar to the scanning confocal microscope Samples made by MBE were key to the discovery of the developed by Marvin Minsky in 1961 and the scanning fractional quantum Hall effect for which the 1998 Nobel acoustic microscope (SAM) developed by Calvin Quate Prize in Physics was awarded. MBE allows scientists to and coworkers in the 1970s, newer scanning probe mi- lay down atomically precise layers of atoms and, in the croscopes have much higher resolution, since they are not process, build up complex structures. Important for re- limited by the wavelength of sound or light. search on semiconductors, MBE is also widely used to The tip of a scanning probe can also be used to manip- make samples and devices for the newly emerging field ulate nanostructures (a process called positional assem- of spintronics. bly). Feature-oriented scanning methodology may be a However, new therapeutic products, based on respon- promising way to implement these nanomanipulations in sive nanomaterials, such as the ultradeformable, stress- automatic mode.*[44]*[45] However, this is still a slow sensitive Transfersome vesicles, are under development process because of low scanning velocity of the micro- and already approved for human use in some countries. scope. 46 CHAPTER 6. NANOTECHNOLOGY

6.5 Applications memory thanks to nanotechnology.*[48] Nanotechnol- ogy may have the ability to make existing medical applications cheaper and easier to use in places like the general practitioner's office and at home.*[49] Cars are being manufactured with nanomaterials so they may need fewer metals and less fuel to operate in the future.*[50] Scientists are now turning to nanotechnology in an attempt to develop diesel engines with cleaner exhaust fumes. Platinum is currently used as the diesel engine catalyst in these engines. The catalyst is what cleans the exhaust fume particles. First a reduction catalyst is em- ployed to take nitrogen atoms from NOx molecules in or- One of the major applications of nanotechnology is in the area of der to free oxygen. Next the oxidation catalyst oxidizes nanoelectronics with MOSFET's being made of small nanowires the hydrocarbons and carbon monoxide to form carbon ~10 nm in length. Here is a simulation of such a nanowire. dioxide and water.*[51] Platinum is used in both the reduction and the oxidation catalysts.*[52] Using platinum though, is inefficient in that it is expensive and unsustain- able. Danish company InnovationsFonden invested DKK 15 million in a search for new catalyst substitutes using nanotechnology. The goal of the project, launched in the autumn of 2014, is to maximize surface area and minimize the amount of material required. Objects tend to minimize their surface energy; two drops of water, for example, will join to form one drop and decrease surface area. If the catalyst's surface area that is exposed to the exhaust fumes is maximized, efficiency of the catalyst is maximized. The team working on this project aims to create nanoparticles that will not merge. Every time the surface is optimized, material is saved. Thus, creating these nanoparticles will increase the effectiveness of the ̶ Nanostructures provide this surface with superhydrophobicity, resulting diesel engine catalyst in turn leading to cleaner which lets water droplets roll down the inclined plane. exhaust fumes̶and will decrease cost. If successful, the team hopes to reduce platinum use by 25%.*[53] Main article: List of nanotechnology applications Nanotechnology also has a prominent role in the fast developing field of Tissue Engineering. When designing As of August 21, 2008, the Project on Emerging Nan- scaffolds, researchers attempt to the mimic the nanoscale otechnologies estimates that over 800 manufacturer- features of a Cell's microenvironment to direct its dif- * identified nanotech products are publicly available, with ferentiation down a suitable lineage. [54] For example, new ones hitting the market at a pace of 3–4 per when creating scaffolds to support the growth of bone, * week.*[13] The project lists all of the products in a pub- researchers may mimic osteoclast resorption pits. [55] licly accessible online database. Most applications are Researchers have successfully used DNA origami-based limited to the use of “first generation”passive nano- nanobots capable of carrying out logic functions to materials which includes titanium dioxide in sunscreen, achieve targeted drug delivery in cockroaches. It is said cosmetics, surface coatings,*[46] and some food prod- that the computational power of these nanobots can be ucts; Carbon allotropes used to produce gecko tape; silver scaled up to that of a Commodore 64.*[56] in food packaging, clothing, disinfectants and household appliances; zinc oxide in sunscreens and cosmetics, surface coatings, paints and outdoor furniture varnishes; and cerium oxide as a fuel catalyst.*[12] 6.6 Implications Further applications allow tennis balls to last longer, golf balls to fly straighter, and even bowling balls to become Main article: Implications of nanotechnology more durable and have a harder surface. Trousers and socks have been infused with nanotechnology so that they An area of concern is the effect that industrial-scale will last longer and keep people cool in the summer. manufacturing and use of nanomaterials would have on Bandages are being infused with silver nanoparticles to human health and the environment, as suggested by heal cuts faster.*[47] Video game consoles and personal nanotoxicology research. For these reasons, some groups computers may become cheaper, faster, and contain more advocate that nanotechnology be regulated by govern- 6.7. REGULATION 47 ments. Others counter that overregulation would stifle Researchers have found that when rats breathed in scientific research and the development of beneficial in- nanoparticles, the particles settled in the brain and lungs, novations. Public health research agencies, such as the which led to significant increases in biomarkers for in- National Institute for Occupational Safety and Health are flammation and stress response*[68] and that nanoparti- actively conducting research on potential health effects cles induce skin aging through oxidative stress in hairless stemming from exposures to nanoparticles.*[57]*[58] mice.*[69]*[70] Some nanoparticle products may have unintended conse- A two-year study at UCLA's School of Public Health quences. Researchers have discovered that bacteriostatic found lab mice consuming nano-titanium dioxide showed silver nanoparticles used in socks to reduce foot odor DNA and chromosome damage to a degree “linked to are being released in the wash.*[59] These particles are all the big killers of man, namely cancer, heart disease, then flushed into the waste water stream and may destroy neurological disease and aging”.*[71] bacteria which are critical components of natural ecosys- * A major study published more recently in Nature Nan- tems, farms, and waste treatment processes. [60] otechnology suggests some forms of carbon nanotubes – Public deliberations on risk perception in the US and UK a poster child for the“nanotechnology revolution”– could carried out by the Center for Nanotechnology in Soci- be as harmful as asbestos if inhaled in sufficient quan- ety found that participants were more positive about nan- tities. Anthony Seaton of the Institute of Occupational otechnologies for energy applications than for health ap- Medicine in Edinburgh, Scotland, who contributed to the plications, with health applications raising moral and eth- article on carbon nanotubes said“We know that some of ical dilemmas such as cost and availability.*[61] them probably have the potential to cause mesothelioma. Experts, including director of the Woodrow Wilson Cen- So those sorts of materials need to be handled very care- ”* ter's Project on Emerging Nanotechnologies David Re- fully. [72] In the absence of specific regulation forth- coming from governments, Paull and Lyons (2008) have jeski, have testified*[62] that successful commercialization depends on adequate oversight, risk research strat- called for an exclusion of engineered nanoparticles in food.*[73] A newspaper article reports that workers in a egy, and public engagement. Berkeley, California is currently the only city in the United States to regulate nan- paint factory developed serious lung disease and nanoparticles were found in their lungs.*[74]*[75]*[76]*[77] otechnology;*[63] Cambridge, Massachusetts in 2008 considered enacting a similar law,*[64] but ultimately rejected it.*[65] Relevant for both research on and application of nanotechnologies, the insurability of nanotech- 6.7 Regulation nology is contested.*[66] Without state regulation of nanotechnology, the availability of private insurance for po- Main article: Regulation of nanotechnology tential damages is seen as necessary to ensure that bur- dens are not socialised implicitly. Calls for tighter regulation of nanotechnology have occurred alongside a growing debate related to the human 6.6.1 Health and environmental concerns health and safety risks of nanotechnology.*[78] There is significant debate about who is responsible for the regulation of nanotechnology. Some regulatory agencies currently cover some nanotechnology products and processes (to varying degrees) – by “bolting on”nanotechnology to existing regulations – there are clear gaps in these regimes.*[79] Davies (2008) has proposed a regulatory road map describing steps to deal with these shortcom- ings.*[80] Stakeholders concerned by the lack of a regulatory framework to assess and control risks associated with the release of nanoparticles and nanotubes have drawn parallels with bovine spongiform encephalopathy “( mad cow”dis- A video on the health and safety implications of nanotechnology ease), thalidomide, genetically modified food,*[81] nuclear energy, reproductive technologies, biotechnology, Main articles: Health implications of nanotechnology and asbestosis. Dr. Andrew Maynard, chief science ad- and Environmental implications of nanotechnology visor to the Woodrow Wilson Centerʼs Project on Emerg- ing Nanotechnologies, concludes that there is insufficient Nanofibers are used in several areas and in different prod- funding for human health and safety research, and as a ucts, in everything from aircraft wings to tennis rackets. result there is currently limited understanding of the hu- Inhaling airborne nanoparticles and nanofibers may lead man health and safety risks associated with nanotechnol- to a number of pulmonary diseases, e.g. fibrosis.*[67] ogy.*[82] As a result, some academics have called for 48 CHAPTER 6. NANOTECHNOLOGY

stricter application of the precautionary principle, with • Nanotechnology education delayed marketing approval, enhanced labelling and ad- • Nanotechnology in fiction ditional safety data development requirements in relation to certain forms of nanotechnology.*[83]*[84] • Nanotechnology in water treatment * The Royal Society report [10] identified a risk of • Nanoweapons nanoparticles or nanotubes being released during dis- posal, destruction and recycling, and recommended that • National Nanotechnology Initiative “manufacturers of products that fall under extended pro- • Self-assembly of nanoparticles ducer responsibility regimes such as end-of-life regulations publish procedures outlining how these materials • Top-down and bottom-up will be managed to minimize possible human and envi- • ronmental exposure”(p. xiii). Translational research The Center for Nanotechnology in Society has found • Wet nanotechnology that people respond to nanotechnologies differently, depending on application – with participants in public deliberations more positive about nanotechnologies for en- 6.9 References ergy than health applications – suggesting that any public calls for nano regulations may differ by technology sec- [1] Drexler, K. Eric (1986). Engines of Creation: The Coming tor.*[61] Era of Nanotechnology. Doubleday. ISBN 0-385-19973- 2. [2] Drexler, K. Eric (1992). Nanosystems: Molecular Ma- 6.8 See also chinery, Manufacturing, and Computation. New York: John Wiley & Sons. ISBN 0-471-57547-X. Main article: Outline of nanotechnology [3] Apply nanotech to up industrial, agri output, The Daily Star (Bangladesh), 17 April 2012. [4] Saini, Rajiv; Saini, Santosh; Sharma, Sugandha (2010). • Bionanoscience “Nanotechnology: The Future Medicine”. Jour- • Carbon nanotube nal of Cutaneous and Aesthetic Surgery 3 (1): 32–33. doi:10.4103/0974-2077.63301. PMC 2890134. PMID • Energy applications of nanotechnology 20606992.

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6.11 Text and image sources, contributors, and licenses

6.11.1 Text

• Superconductivity Source: https://en.wikipedia.org/wiki/Superconductivity?oldid=708066892 Contributors: AxelBoldt, Lee Daniel Crocker, CYD, Bryan Derksen, AstroNomer, Andre Engels, DavidLevinson, Quintanilla, Jqt, Azhyd, Waveguy, David spector, Heron, Olivier, Edward, Michael Hardy, Fred Bauder, DopefishJustin, Dominus, Karada, Tiles, Egil, Ahoerstemeier, Stevenj, Theresa knott, Snoyes, Julesd, Glenn, Cimon Avaro, GCarty, Cryoboy, Mxn, Tantalate, Reddi, Stone, Joerg Reiher~enwiki, Hao2lian, DJ Clayworth, E23~enwiki, Furrykef, Taxman, LMB, Fibonacci, Omegatron, Traroth, Topbanana, Pstudier, Pakaran, Phil Boswell, Donarreiskoffer, Robbot, Stephan Schulz, Rorro, Bkell, Hadal, UtherSRG, Robinh, Diberri, Cyberpunks~enwiki, Connelly, Giftlite, DocWatson42, MarkP- Neyer, Harp, Tom harrison, Ferkelparade, Fastfission, Xerxes314, Leonard G., Foobar, Bobblewik, Wmahan, Irarum, Geni, Quadell, Spi- ralhighway, Icairns, Peter bertok, Gerrit, Deglr6328, Deeceevoice, Moxfyre, Reflex Reaction, Zowie, CALR, Discospinster, FT2, Rama, Vsmith, Pavel Vozenilek, Paul August, Andrejj, Kaisershatner, CanisRufus, Kwamikagami, PhilHibbs, Haxwell, Simonbp, Femto, Dalf, Bobo192, BrokenSegue, Enric Naval, Slicky, Kjkolb, Nk, Merope, PaulHanson, GiantSloth, Lightdarkness, Sligocki, Pion, Hu, Velella, Wt- shymanski, Evil Monkey, RJFJR, Cmapm, Dfalkner, Gene Nygaard, Aeronautics, RHaworth, Dandv, StradivariusTV, Oliphaunt, Jeff3000, Jwanders, Alfakim, Firien, Triddle, Someone42, GregorB, Eras-mus, CharlesC, SeventyThree, Christopher Thomas, Graham87, Magis- ter Mathematicae, Jan van Male, Josh Parris, Sjö, Sjakkalle, Rjwilmsi, Seidenstud, Fish and karate, FlaBot, PhilipSargent, Jeepo~enwiki, Gurch, Leslie Mateus, Fosnez, Goudzovski, Skierpage, Chobot, DVdm, Ahpook, Takaaki, Roboto de Ajvol, The Rambling Man, Wave- length, Mollsmolyneux, Bhny, JabberWok, Netscott, Hydrargyrum, CambridgeBayWeather, Salsb, GeeJo, Harksaw, Długosz, RyanLiv- ingston, Ino5hiro, Mkouklis, Nineteenthly, Mccready, Dhollm, Scottfisher, Quarky2001, DeadEyeArrow, Oliverdl, Tonym88, Codell, Searchme, Light current, 2over0, DaveOinSF, Theda, Closedmouth, Bamse, Filou~enwiki, Petri Krohn, JoanneB, Alias Flood, Wylie440, Chaiken, SkerHawx, Kgf0, Children of the dragon, SmackBot, Melchoir, Gilliam, Oscarthecat, Chaojoker, Kmarinas86, Chris the speller, RevenDS, NCurse, Thumperward, Papa November, Complexica, AtmanDave, Kostmo, Dual Freq, Trekphiler, KaiserbBot, TheKMan, LouScheffer, Elendil's Heir, Toomontrangle, Pwjb, Smokefoot, Eynar, DMacks, Paulish, Simon Arnold, Lester, Nbishop, Breadbox, Kuru, John, JorisvS, Smartyllama, Manjish, IronGargoyle, Dicklyon, Spiel496, Citicat, Majormcmuffin, Kvng, Astrobradley, JarahE, KJS77, Brienanni, Japhet, Hmtamza, Tawkerbot2, Chetvorno, CmdrObot, Van helsing, MorkaisChosen, CBM, WMSwiki, Tim1988, Lokal Pro- fil, Phatom87, Britannic~enwiki, Cydebot, Kam42705, Neil Froschauer, Chasingsol, Myscrnnm, Lee, IComputerSaysNo, Arwen4014, Editor at Large, TrevorRC, Matwilko, Raschd, Epbr123, Kubanczyk, Dasacus, Headbomb, Dgies, Dawnseeker2000, Cyclonenim, Court- jester555, Mojohaza1, Casomerville, Yellowdesk, JAnDbot, Quentar~enwiki, Smartcat, Bongwarrior, VoABot II, Ginga2, SineWave, Jjasi, Web-Crawling Stickler, Dirac66, Coolkoon, Limtohhan, Joshua Davis, Schmloof, Xantolus, CommonsDelinker, Pharaoh of the Wizards, Jtw11, Dmrmatt19, Hans Dunkelberg, Uncle Dick, Maurice Carbonaro, Nigholith, MrBell, Eliz81, Bakkouz, Rod57, Bot-Schafter, Tomy- Duby, Anatoly larkin, Wimox, Equazcion, Tevonic, Useight, Qaz123qaz, Bertiethecat, Idioma-bot, JeffreyRMiles, VolkovBot, TXiKiBoT, Neha simon, Calwiki, Hqb, Liquidcentre, JosephJohnCox, OlavN, Sodapopinski, Robert1947, Burntsauce, Elecwikiman, Fischer.sebastian, AlleborgoBot, Shanmugammpl, Runewiki777, Steven Weston, SieBot, Yintan, Vanished User 8a9b4725f8376, FSUlawalumni, Keilana, Hzh, Henry Delforn (old), Onopearls, Anchor Link Bot, Hamiltondaniel, Geoff Plourde, Elliott-rhodes, TubularWorld, Tegrenath, Lar- Ran, ClueBot, Trojancowboy, Fuzzylunkinz, Ctiefel, Techdawg667, VsBot, YBCO, Niceguyedc, Rotational, Cousins.inc, CohesionBot, Jeck1335, Doctorpsi, PixelBot, Bob man801, Lartoven, Brews ohare, Neucleon, Natty sci~enwiki, Doprendek, SchreiberBike, Aitias, Sub- ash.chandran007, Viktor O. Ledenyov, SoxBot III, HumphreyW, LSTech, Tarlneustaedter, Wertuose, BodhisattvaBot, Rror, Ngebbett, Ost316, WikHead, Noctibus, ElMeBot, Addbot, Forscite, AVand, DOI bot, Melab-1, Travisoto, Flning, Jncraton, CanadianLinuxUser, Leszek Jańczuk, CarsracBot, Dr. Universe, K Eliza Coyne, Gwcdt, Lightbot, SPat, Luckas-bot, Yobot, Fraggle81, THEN WHO WAS PHONE?, CinchBug, Csmallw, MassimoAr, AnomieBOT, Cryogenics, Guff2much, Materialscientist, Citation bot, Xqbot, Eep not for fat people, Waleswatcher, NinjaDreams, Janolaf30, Dave3457, GliderMaven, FrescoBot, WikiMcGowan, Tobby72, AlanDewey, Citation bot 1, ASchwarz, Pinethicket, HRoestBot, Schrodingers rabbit, 10metreh, Tom.Reding, Gruntler, Richardc03, Mikespedia, Heller2007, Felix0411, Trappist the monk, Anoop ranjan, Aleitner, Ahsbenton, Agnel P.B., Catcamus, Akoufos, Jiyojolly, Dick Chu, Noommos, Haj33, EmausBot, John of Reading, WikitanvirBot, DonyG, JasonSaulG, Mathew10111, Pascalf, K6ka, Hhhippo, ManosHacker, Medeis, A930913, A.sav, Tls60, Sailsbystars, Nothingbutdreamer, ChuispastonBot, AndyTheGrump, DASHBotAV, WikiBaller, ClueBot NG, Gilderien, Hightc, Widr, Names are hard to think of, Helpful Pixie Bot, Sina.zapf, Mightyname, Nightenbelle, Jubobroff, Bibcode Bot, BG19bot, Virtualerian, Island Monkey, Ymblanter, Andol, WikiHacker187, Mark Arsten, 52 6f 62, Pong711, BattyBot, Bv.vasiliev, Chim02, MahdiBot, Jimw338, Embrittled, Adwaele, Protectionwi, Dexbot, Anandaraja, Oliver brookes, Fittold27, TwoTwoHello, Andy- howlett, Reatlas, Ruby Murray, François Robere, Rabbitflyer, Asik Ram, Monkbot, Trackteur, Jrafner, Aruppillai, Laurencejwolf, Scipsy- cho, OzRamos, KasparBot, Superspin, Shao xc, PJRay and Anonymous: 527 • Meissner effect Source: https://en.wikipedia.org/wiki/Meissner_effect?oldid=707525371 Contributors: Bryan Derksen, William Avery, Jqt, FlorianMarquardt, Michael Hardy, Tim Starling, Julesd, Mxn, Wikiborg, David.Monniaux, Shantavira, PuzzletChung, Rorro, Oji- giri~enwiki, Tobias Bergemann, Nethershaw, Harp, Suspekt~enwiki, Ebear422, Discospinster, Agnistus, ChristophDemmer, Svdmolen, Di- amonddavej, Jaguar2k, Zetawoof, Wricardoh~enwiki, RJFJR, Gene Nygaard, Yansa, Louise Rill, Milez, Vanderdecken, Saperaud~enwiki, Rjwilmsi, Coemgenus, Syndicate, FlaBot, DaGizza, Jernejl, YurikBot, Petiatil, Netscott, David R. Ingham, Quarky2001, Tetracube, Ninly, HereToHelp, Alureiter, Sardanaphalus, SmackBot, Ennorehling, Bluebot, Pieter Kuiper, DHN-bot~enwiki, Sim man, Wen D House, Eynar, Siddharth srinivasan, Eleider, The age of fable, BananaFiend, RekishiEJ, Mr Evil, CapitalR, Ewulp, Kthemank, Nutster, Meisam.fa, Dagger- stab, Sunilvarma.d, WeggeBot, WMSwiki, Cydebot, Robertinventor, Thijs!bot, Headbomb, Electron9, Escarbot, Geelen, Kent Witham, Qwerty Binary, BailesB, Igodard, Johnman239, WLU, Xenocide321, Verdatum, Choihei, Cuzkatzimhut, Larryisgood, Spinningspark, Why Not A Duck, Nibios, AlleborgoBot, Johnvonahlen, SieBot, BotMultichill, Gerakibot, LeadSongDog, Perspicacite, Oxymoron83, R0uge, Cyfal, Dodecagon, Neo., ClueBot, PipepBot, The Thing That Should Not Be, EoGuy, YBCO, Vijayaraj83, Iceman9985, Pixel- Bot, Zomno, Dsmurat, Versus22, XLinkBot, Ost316, Addbot, Vze2wgsm1, LaaknorBot, K Eliza Coyne, Lightbot, Teles, DrFO.Tn.Bot, Legobot, Luckas-bot, Yobot, AnomieBOT, Jim1138, Materialscientist, The High Fin Sperm Whale, Friendofthefoot, V35b, Jacques- bezuidenhout, Almabot, GrouchoBot, Waleswatcher, Shadowjams, FrescoBot, D'ohBot, Citation bot 1, RedBot, Nobody267, Aleitner, Clarkcj12, User071, Dick Chu, AnonNemoVoid, EmausBot, Pgm944, Slightsmile, K6ka, Circuitboardsushi, MisterDub, Martin3141, Mayur, Tls60, ChuispastonBot, RockMagnetist, Llightex, ClueBot NG, Cwmhiraeth, Gareth Griffith-Jones, Jorgecarleitao, Helpful Pixie Bot, Bibcode Bot, Bokbindaren, Qwerty937, Jw2036, Erasmusbee, Embrittled, Hcarter333, TwoTwoHello, FlutteringCarp, Physicisttoo, Monkbot, WordSeventeen, Zordman1 and Anonymous: 127 • Technological applications of superconductivity Source: https://en.wikipedia.org/wiki/Technological_applications_of_ superconductivity?oldid=696096482 Contributors: Quintanilla, Azhyd, Heron, Crenner, LMB, Finlay McWalter, Rorro, Kaiser- shatner, Ultramarine, UTF-8, Wolfe604, Mindmatrix, Rjwilmsi, PhilipSargent, SmackBot, Lainagier, Polonium, Simon Arnold, Jaganath, 6.11. TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES 53

Politepunk, Dycedarg, Dgw, N2e, Simon arnold, Kanags, Rod57, Knulclunk, Flyer22 Reborn, Henry Delforn (old), Techman224, Chem-awb, Mild Bill Hiccup, Auntof6, WikiDao, Forscite, Zahd, SpellingBot, 2D, Janolaf30, FrescoBot, TGCP, Tls60, Thampiajit, G.Kiruthikan and Anonymous: 27 • SQUID Source: https://en.wikipedia.org/wiki/SQUID?oldid=707679432 Contributors: TwoOneTwo, Rmhermen, William Avery, Tzartzam, Twilsonb, RTC, Collabi, Ahoerstemeier, Julesd, Glenn, 4lex, Maximus Rex, Finlay McWalter, Robbot, Rorro, Carnildo, Wizzy, DavidCary, Niteowlneils, Frencheigh, McE~enwiki, Finn-Zoltan, Gzuckier, Symmetry, Jkl, Rich Farmbrough, El C, Walkiped, Slicky, Mr2001, Ynhockey, Bucephalus, Gene Nygaard, Falcorian, Linas, Polyparadigm, Robert K S, GregorB, Dbutler1986, Eteq, Saperaud~enwiki, Rjwilmsi, Eubot, Chobot, Krishnavedala, YurikBot, David Woodward, Gaius Cornelius, DavidConrad, Tjarrett, Tony1, Zwobot, Scottfisher, Kkmurray, Cspalletta, Tyrhinis, SmackBot, Xlez8057, Chaojoker, Chris the speller, Thumperward, Colonies Chris, Tsca.bot, Stevenmitchell, Lostart, Rolinator, Onionmon, DabMachine, Marcusl, Brendanlevy, Tawkerbot2, E goldobin, Zureks, N2e, Sahrin, Supremeknowledge, Dr.enh, Thijs!bot, Arcresu, Tirkfl, Oosh, 1-54-24, Luna Santin, JAnDbot, Skomorokh, Twarge, Ariel., Vzapf, Nono64, Flyguy0507, Rod57, Saryakhran, ArqMage, Holme053, LokiClock, TXiKiBoT, Mercurywoodrose, CoJaBo, Erikev, Andy Dingley, AstroNerd2000, 4RM0~enwiki, Rmn1791, Barriga.a.s, Chem-awb, Trojancowboy, ChandlerMapBot, ParisianBlade, Viktor O. Ledenyov, Dthomsen8, Addbot, Mr0t1633, RPHv, JGKlein, Lightbot, Luckas-bot, Yobot, Aldebaran66, AnomieBOT, Piano non troppo, Crystal whacker, Materialscientist, Citation bot, FrescoBot, Pepper, Citation bot 1, Sheetals magnetics, I dream of horses, Talkirz, Black- baud, SingingZombie, Bobby122, RjwilmsiBot, Hhhippo, ClueBot NG, David C Bailey, Xavier Thibault, Mailme.kpriyadharsan, Helpful Pixie Bot, Bibcode Bot, BG19bot, Cyberbot II, Adwaele, Dexbot, Angufan, Jharrism2, Fedora99, DAsia, HRDVinc and Anonymous: 105 • Maglev Source: https://en.wikipedia.org/wiki/Maglev?oldid=710584440 Contributors: Bryan Derksen, Maury Markowitz, JDG, Rick- yrab, Edward, Patrick, Michael Hardy, Modster, Mahjongg, Delirium, Ahoerstemeier, Mac, Jpatokal, Reddi, Johnh123, Tpbradbury, Pacific1982, Rei, Omegatron, Mackensen, Marc omorain, Bloodshedder, Finlay McWalter, Slawojarek, Shantavira, Robbot, Sdedeo, Pigsonthewing, Chrism, Altenmann, Lowellian, KSweeley, Polonius, Henrygb, Academic Challenger, Blainster, Mattflaschen, Giftlite, DavidCary, Wolfkeeper, BenFrantzDale, Tom harrison, Marcika, Nelso, Chinasaur, RScheiber, Falcon Kirtaran, Python eggs, Bobblewik, Golbez, Alex Libman, Gugganij, Comatose51, SoWhy, Pgan002, Antandrus, Beland, Kusunose, Gunnar Larsson, Kiteinthewind, Maxi- maximax, Houshuang, Englishdude, Mathilda~enwiki, Hellisp, Willhsmit, ArthurDenture, Naus, Calwatch, Trevor MacInnis, Chrisbolt, Snuffkin~enwiki, Jayjg, Freakofnurture, Miborovsky, Indosauros, NathanHurst, Chris j wood, Discospinster, Avriette, Sladen, Clawed, Vsmith, Pmaccabe, Aris Katsaris, Eric Shalov, Michael Zimmermann, Sarrica, Deelkar, Aperculum, MarkS, Bender235, Kaisershatner, FriedBunny, Konstantin~enwiki, Tompw, Huntster, Bletch, Hayabusa future, Shanes, RoyBoy, Yanzi, Bobo192, AmosWolfe, Smalljim, Cmdrjameson, .:Ajvol:., Cwolfsheep, Cavrdg, Slambo, Pearle, Hooperbloob, Foxandpotatoes, Dygituljunky, Yalbik, Merope, Beyondthis- life, Danski14, Mrzaius, Alansohn, Vslashg, 119, Arthena, Slof, 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Exeunt, Cydebot, Ryan, Grammaticus Repairo, Enoch the red, Odie5533, DumbBOT, Chrislk02, YorkBW, Monster eagle, Tornados28, FrancoGG, Thijs!bot, Epbr123, Sonderbro, Diogo Almeida, Kablammo, Gralo, WilliamH, John254, Uv411, Ufwuct, Dark Enigma, Tellyaddict, Cool Blue, Davidhorman, Cooljuno411, Stannered, Niduzzi, AntiVandalBot, WinBot, Chaleyer61, Luna Santin, Seaphoto, Hensu75, XOXOLIZ, Bigtimepeace, Prolog, Qasdfdsaq, Zylorian, Darklilac, A.M.962, Gdo01, Kzaral, Lfstevens, Carewolf, Srihariramadas, Myanw, Cpzilliacus, Gökhan, Ingolfson, Deadbeef, JAnD- bot, MER-C, Mrspaceman, RiseOfTheRev01ution, Plm209, Andonic, Hut 8.5, Zack2007, Acroterion, SteveSims, Gert7, Animaly2k2, Magioladitis, Bongwarrior, VoABot II, Nyq, Wikidudeman, Salinecjr, Jetstreamer, Kuyabribri, JNW, Pixel ;-), Shablog, Catgut, Theroad- islong, Steevm, Elentirmo, IkonicDeath, Acornwithwings, 28421u2232nfenfcenc, Greg Grahame, A3nm, Monalisaoverdrive, Tailsfan2, Glen, Edward321, Filik, Robin S, Lost tourist, Hintswen, Otvaltak, Stephenchou0722, S3000, Atarr, AVRS, Cliff smith, MartinBot, Ghorbanalibeik, The Lord Of The Dance, Halpaugh, Xantolus, Rettetast, Sm8900, FI-psych3, Nickpunt, R'n'B, CommonsDelinker, Qrex123, Cicero UK, Lilac Soul, Tgeairn, J.delanoy, Captain panda, Timtjervis, Uncle Dick, All Is One, Dbiel, MrBell, PhoenixBlitzkrieg, Tdadamemd, Hisagi, LordAnubisBOT, McSly, Grayoshi, Sebwite, Bailo26, Ephebi, Pyrospirit, AntiSpamBot, (jarbarf), Plasticup, Talk- boy11, Gregfitzy, Cobi, Shoessss, Hanacy, KylieTastic, Korranus, SirJibby, Launchpoint, Tiggerjay, Jamesontai, Tellerman, DMCer, Gtg204y, Czarbender, Andy Marchbanks, Mlivesey, Geeked, Izno, KGV, Soccerman11a, Spellcast, Lights, X!, Deor, Netmonger, Kyle kyle is 50, Raphaelmak, VolkovBot, The Wild Falcon, Christophenstein, Jeff G., Alexandria, AlnoktaBOT, SergeyKurdakov, Kyle the bot, Ryan032, Philip Trueman, PNG crusade bot, Matttster37, Oshwah, Malinaccier, Technopat, Kritikos99, Devoxo, Qxz, Someguy1221, DennyColt, Leafyplant, Jackfork, LeaveSleaves, Ephix, Sushiya, Wiae, InfinityAndBeyond, Donald.s.armstrong, Evan575, Andy Dingley, Falcon8765, Iapain wiki, Burntsauce, Typ932, Quevvy, Frksforjesus, Thric3, JMT~enwiki, Tumadoireacht, Finnrind, Lieutenantmudd, SieBot, Moebiusuibeom-en, Jauerback, Noveltyghost, MaltaGC, Jacotto, Theup3985, Swaq, Yintan, Bentogoa, Flyer22 Reborn, Wheel- ieBinner, Number1schumacherfan, Oxymoron83, XxXXMULLIGANXXxx, KoshVorlon, Lightmouse, RW Marloe, Francisco Tevez, 54 CHAPTER 6. NANOTECHNOLOGY

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ChrassLovesEmma, Balsone1990, Kwjbot, Badgernet, Tomshen, Alexius08, Arifhussaintm, ElMeBot, Airplaneman, Shmay, Sachinrocks, RyanCross, Lilgoni, HexaChord, Dark Gaia, Asbian513, Issius, Addbot, ERK, SFKatUMO, Bedrokdamian, Cheaptubes, Some jerk on the Internet, DOI bot, Esmash, Non-dropframe, Captain-tucker, Friginator, Blechnic, Blueelectricstorm, ChrisViper, Ronhjones, Tutter- Mouse, Dr SHOEB82, Mww113, CanadianLinuxUser, Corporate4, AcademyAD, Wælgæst wæfre, MrOllie, Download, Charliebigpota- toes, Chamal N, Figarow, PranksterTurtle, Pechotat, Glane23, Chzz, AnnaFrance, Jasper Deng, AkSahota312, 84user, Numbo3-bot, Naveenlingam, Ronaldo wanna b, Ben Wraith, Tide rolls, Jenita JJ, Lightbot, Gail, Loupeter, Ettrig, Tikar aurum, LuK3, Hoborobo234, Legobot, Math Champion, Luckas-bot, Nanojames, Yobot, 2D, Tohd8BohaithuGh1, Les boys, II MusLiM HyBRiD II, Nallimbot, Ame- liorationBot, Tempodivalse, AnomieBOT, Andrewrp, IRP, Piano non troppo, Mattjharrison, AdjustShift, Soxwon, Kingpin13, Law, Flewis, Timspencer1, Materialscientist, Elmmapleoakpine, Syke22, Citation bot, OllieFury, NanoIQP, Roux-HG, ArthurBot, Gammara- ptor, Nanoorg, 1234eatmoore, Xqbot, TheAMmollusc, Cpichardo, 450hondarider, Rice888, Sionus, Anoxonian, Addihockey10, JimVC3, NHL09addict, Capricorn42, Jeffrey Mall, Erpreeti, Mrba70, Luckyleafus, P99am, Almabot, Mrmattyboy, Nayvik, Nanodic, Saeed5252, Adecoco, RibotBOT, Nanoshel, Zenith87, Logger9, SteveKSmith, Likemike232, Kirsted, Shadowjams, StimsonsGhetto1, WhatisFeel- ings?, Reaver789, Reimarspohr, Mxb design, Antorourke, FrescoBot, Baz.77.243.99.32, Prettyperky, Nmedard, Illustria, Gatorguy13, Emiles93, Michael93555, Recognizance, Colin Ryan, Nickvalcke, D'ohBot, Smevy, VI, Gleeson 44, A Real Live One, Jamesooders, Arcendet, Intelligentsium, Ryza0708, Mimzy1990, MacMed, I dream of horses, Abani79, Notedgrant, Dr-b-m, RedBot, MastiBot, Fauncet, Serols, SpaceFlight89, Wizkid291, Fartherred, Dmberube, Jauhienij, Oklahombre, FoxBot, Aakashrajain, Ertugrul.Bülbül, Mathiasoutrae- gus, Trappist the monk, Maercli, DriveMySol, Shinels12, Kamleshshah21, Vrenator, Kishan88, Devonmbr, IVila, Tbhotch, Twocentsplain, Dennimen, Cmarz, RjwilmsiBot, Ouji-fin, TjBot, Ayaazzz, Chemyanda, Me10113, Socialjest404, Petermcelwee, DASHBot, EmausBot, John of Reading, Beatnik8983, Dewritech, RA0808, Markopetek, NotAnonymous0, Solarra, Tommy2010, Wikipelli, NanoTechReader, K6ka, Ilikepie121, Thecheesykid, Mz7, Ida Shaw, Fæ, Kokopellimama, Bob123456788, Sthubertus, Looscan, RaptureBot, Firesnake1995, Donner60, Jasbirsingheng, Vimal samuthiravel, Rangoon11, LikeLakers2, LZ6387, Efiiamagus, Petrb, ClueBot NG, Nanoink1, Manubot, Singhmahendra20, Rebeccarz, Veritasvoswiki, Mite veles, 123Hedgehog456, O.Koslowski, Morpheus1st, Muon205, Priyaviji, Karen- nano, Helpful Pixie Bot, KD888, Bibcode Bot, Reinstenanoventures, Nick205228, Waterball391, Lowercase sigmabot, BG19bot, Virtua- lerian, Citronen95, Ymblanter, Wasbeer, Vagobot, Wiki13, Ewigekrieg, MusikAnimal, Amp71, Mark Arsten, Ingmar.lippert, Cadiomals, Shisha-Tom, BattyBot, Mdann52, Cyberbot II, Padenton, IjonTichyIjonTichy, Dexbot, Webclient101, Mogism, JZNIOSH, Leafonesky, Lugia2453, Frosty, Detabudash, Poopshady, Funny2002, DATCAM, Shashwat gokhe, Nanops nanotechnology, Eyesnore, Eahille, Aflusty, Cibits, Firestorme50, CensoredScribe, Haminoon, Fasantos, Thevideodrome, LatinumPulchrum, Williamleach510, Saeid196721, Gahar- 56 CHAPTER 6. NANOTECHNOLOGY

war, Conde.bio, Mahusha, Monkbot, Nano.pfpa, SantiLak, Trackteur, FNI214, BraveAce, James69696969, Urquijog, AMResearchNext1, Nanotech33, Ofkingskinga, Upadhyayakishor, Manusvelox, Orduin, Wyclef Nzavi, Soltan715, CPPOLS, Pitchcapper, Ebrakeﬁeld23, Tutormatic, Abierma3, Aadam469, Ibukharix, Coolkjk, Dimapoet, Aryansaw03, Y2N1-09631, Zebrapolar, KasparBot, Onthegay, Ru- biksCube7, Boisewired, Pengyulong7, Hfslt, PeinTwen, Lr0^^k, Fabiochu, James Hare (NIOSH), TomTomRenRen, DirtyRotten, Om- nidrone, Goshtasbc, Jrober22 and Anonymous: 2001

6.11.2 Images • File:A-simple-and-fast-fabrication-of-a-both-self-cleanable-and-deep-UV-antireflective-quartz-1556-276X-7-430-S1.ogv Source: https://upload.wikimedia.org/wikipedia/commons/6/6d/A-simple-and-fast-fabrication-of-a-both-self-cleanable-and-deep-UV-antireflective-quartz-1556-276X-7-430-S1. ogv License: CC BY 2.0 Contributors: Kim J, Jeong H, Lee W, Park B, Kim B, Lee K (2012). “A simple and fast fabrication of a both self-cleanable and deep-UV antireﬂective quartz nanostructured surface”. Nanoscale Research Letters. DOI:10.1186/1556-276X-7-430. PMID 22853428. Original artist: Kim J, Jeong H, Lee W, Park B, Kim B, Lee K • File:AFMsetup.jpg Source: https://upload.wikimedia.org/wikipedia/commons/5/5e/AFMsetup.jpg License: CC BY 2.5 Contributors: http://kristian.molhave.dk Original artist: yashvant • File:A_maglev_train_coming_out,_Pudong_International_Airport,_Shanghai.jpg Source: https://upload.wikimedia.org/ wikipedia/commons/d/d1/A_maglev_train_coming_out%2C_Pudong_International_Airport%2C_Shanghai.jpg License: Public domain Contributors: Originally from en.wikipedia; description page is (was) here Original artist: User Alex Needham (own photography) on en.wikipedia • File:Achermann7RED.jpg Source: https://upload.wikimedia.org/wikipedia/commons/c/c7/Achermann7RED.jpg License: Public domain Contributors: Los Alamos National Laboratory, http://www.sandia.gov/news-center/news-releases/2004/micro-nano/well.html Orig- inal artist: Marc Achermann • File:Ambox_current_red.svg Source: https://upload.wikimedia.org/wikipedia/commons/9/98/Ambox_current_red.svg License: CC0 Contributors: self-made, inspired by Gnome globe current event.svg, using Information icon3.svg and Earth clip art.svg Original artist: Vipersnake151, penubag, Tkgd2007 (clock) • File:Atomic_resolution_Au100.JPG Source: https://upload.wikimedia.org/wikipedia/commons/e/ec/Atomic_resolution_Au100.JPG License: Public domain Contributors: ? Original artist: ? • File:Birmingham_International_Maglev.jpg Source: https://upload.wikimedia.org/wikipedia/commons/f/f5/Birmingham_ International_Maglev.jpg License: CC BY-SA 3.0 Contributors: Own work Original artist: MaltaGC • File:C60_Buckyball.gif Source: https://upload.wikimedia.org/wikipedia/commons/3/32/C60_Buckyball.gif License: CC BY 3.0 Con- tributors: Crystal Viewer Tool on www.nanoHUB.org. Link: http://nanohub.org/resources/8793 Original artist: Saumitra R Mehrotra & Gerhard Klimeck • File:C60a.png Source: https://upload.wikimedia.org/wikipedia/commons/4/41/C60a.png License: CC-BY-SA-3.0 Contributors: Trans- ferred from en.wikipedia to Commons. Original artist: The original uploader was Mstroeck at English Wikipedia Later versions were uploaded by Bryn C at en.wikipedia. • File:CERN-cables-p1030764.jpg Source: https://upload.wikimedia.org/wikipedia/commons/c/cc/CERN-cables-p1030764.jpg License: CC BY-SA 2.0 fr Contributors: Own work Original artist: Rama • File:Chūō_Shinkansen_map.png Source: https://upload.wikimedia.org/wikipedia/commons/b/b5/Ch%C5%AB%C5%8D_ Shinkansen_map.png License: CC BY-SA 3.0 Contributors: Own work Original artist: Hisagi (氷鷺) • File:Commons-logo.svg Source: https://upload.wikimedia.org/wikipedia/en/4/4a/Commons-logo.svg License: CC-BY-SA-3.0 Contribu- tors: ? Original artist: ? • File:Comparison_of_nanomaterials_sizes.jpg Source: https://upload.wikimedia.org/wikipedia/commons/a/ae/Comparison_of_ nanomaterials_sizes.jpg License: CC BY-SA 3.0 Contributors: http://www.mdpi.com/1422-0067/15/5/7158 Original artist: Sureshbup • File:Crystal_energy.svg Source: https://upload.wikimedia.org/wikipedia/commons/1/14/Crystal_energy.svg License: LGPL Contribu- tors: Own work conversion of Image:Crystal_128_energy.png Original artist: Dhatﬁeld • File:Cvandrhovst.png Source: https://upload.wikimedia.org/wikipedia/commons/0/08/Cvandrhovst.png License: CC-BY-SA-3.0 Con- tributors: ? Original artist: ? • File:DC_SQUID.svg Source: https://upload.wikimedia.org/wikipedia/commons/4/47/DC_SQUID.svg License: CC BY-SA 3.0 Contrib- utors: Own work Original artist: Miraceti • File:DNA_tetrahedron_white.png Source: https://upload.wikimedia.org/wikipedia/commons/a/ad/DNA_tetrahedron_white.png Li- cense: CC BY-SA 3.0 Contributors: Own work Original artist: Antony-22 • File:ECOBEE.jpg Source: https://upload.wikimedia.org/wikipedia/commons/a/a3/ECOBEE.jpg License: CC BY-SA 4.0 Contributors: Own work Original artist: Minseong Kim • File:EfektMeisnera.svg Source: https://upload.wikimedia.org/wikipedia/commons/b/b5/EfektMeisnera.svg License: Public domain Contributors: Inspiration: Image:EXPULSION.png Original artist: Piotr Jaworski, PioM EN DE PL; POLAND/Poznań • File:Ehrenfest_Lorentz_Bohr_Kamerlingh_Onnes.jpg Source: https://upload.wikimedia.org/wikipedia/commons/9/99/Ehrenfest_ Lorentz_Bohr_Kamerlingh_Onnes.jpg License: Public domain Contributors: http://www.luf.nl/site/start.asp?hoofdcategorieID=2& paginaID=365 Original artist: Unknown • File:Flag_of_Germany.svg Source: https://upload.wikimedia.org/wikipedia/en/b/ba/Flag_of_Germany.svg License: PD Contributors: ? Original artist: ? 6.11. TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES 57

• File:Flag_of_Japan.svg Source: https://upload.wikimedia.org/wikipedia/en/9/9e/Flag_of_Japan.svg License: PD Contributors: ? Origi- nal artist: ? • File:Flag_of_the_People'{}s_Republic_of_China.svg Source: https://upload.wikimedia.org/wikipedia/commons/f/fa/Flag_of_the_ People%27s_Republic_of_China.svg License: Public domain Contributors: Own work, http://www.protocol.gov.hk/flags/eng/n_flag/ design.html Original artist: Drawn by User:SKopp, redrawn by User:Denelson83 and User:Zscout370 • File:Flyingsuperconductor.ogg Source: https://upload.wikimedia.org/wikipedia/commons/f/f4/Flyingsuperconductor.ogg License: CC- BY-SA-3.0 Contributors: self made at the Technorama, Winterthur, Switzerland Original artist: Andel Früh • File:Folder_Hexagonal_Icon.svg Source: https://upload.wikimedia.org/wikipedia/en/4/48/Folder_Hexagonal_Icon.svg License: Cc-by- sa-3.0 Contributors: ? 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• File:Series_L0.JPG Source: https://upload.wikimedia.org/wikipedia/commons/a/ac/Series_L0.JPG License: CC BY-SA 3.0 Contribu- tors: Own work Original artist: Saruno Hirobano • File:Squid_prototype.jpg Source: https://upload.wikimedia.org/wikipedia/commons/b/b9/Squid_prototype.jpg License: Public domain Contributors: from NASA, Stanford University. originally uploaded at en.wikip. original description page is/was here[1]. Original artist: original uploader en:User:Slicky • File:Squid_prototype2.jpg Source: https://upload.wikimedia.org/wikipedia/commons/d/db/Squid_prototype2.jpg License: Public domain Contributors: from NASA, Stanford University. originally uploaded at en.wikip. original description page is/was here[1]. Original artist: original uploader en:User:Slicky • File:Stickstoff_gekühlter_Supraleiter_schwebt_über_Dauermagneten_2009-06-21.jpg Source: https://upload.wikimedia.org/ wikipedia/commons/3/3c/Stickstoff_gek%C3%BChlter_Supraleiter_schwebt_%C3%BCber_Dauermagneten_2009-06-21.jpg License: CC BY-SA 3.0 Contributors: Own work Original artist: Henry Mühlpfordt • File:Stylised_Lithium_Atom.svg Source: https://upload.wikimedia.org/wikipedia/commons/e/e1/Stylised_Lithium_Atom.svg License: CC-BY-SA-3.0 Contributors: based off of Image:Stylised Lithium Atom.png by Halfdan. Original artist: SVG by Indolences. Recoloring and ironing out some glitches done by Rainer Klute. • File:Symbol_book_class2.svg Source: https://upload.wikimedia.org/wikipedia/commons/8/89/Symbol_book_class2.svg License: CC BY-SA 2.5 Contributors: Mad by Lokal_Profil by combining: Original artist: Lokal_Profil • File:Symbol_list_class.svg Source: https://upload.wikimedia.org/wikipedia/en/d/db/Symbol_list_class.svg License: Public domain Con- tributors: ? Original artist: ? • File:Telecom-icon.svg Source: https://upload.wikimedia.org/wikipedia/commons/4/4e/Telecom-icon.svg License: Public domain Con- tributors: ? Original artist: ? • File:Threshold_formation_nowatermark.gif Source: https://upload.wikimedia.org/wikipedia/commons/4/43/Threshold_formation_ nowatermark.gif License: Public domain Contributors: Own work Original artist: Saumitra R Mehrotra & Gerhard Klimeck, modified by Zephyris • File:Timeline_of_Superconductivity_from_1900_to_2015.svg Source: https://upload.wikimedia.org/wikipedia/commons/b/bb/ Timeline_of_Superconductivity_from_1900_to_2015.svg License: CC BY-SA 4.0 Contributors: Own work Original artist: PJRay • File:Transrapid-emsland.jpg Source: https://upload.wikimedia.org/wikipedia/commons/0/0f/Transrapid-emsland.jpg License: Public domain Contributors: Own work Original artist: Állatka • File:Transrapid.jpg Source: https://upload.wikimedia.org/wikipedia/commons/9/9b/Transrapid.jpg License: CC-BY-SA-3.0 Contribu- tors: Transderred from dewiki Original artist: Stahlkocher • File:Unbalanced_scales.svg Source: https://upload.wikimedia.org/wikipedia/commons/f/fe/Unbalanced_scales.svg License: Public domain Contributors: ? Original artist: ? • File:Wikibooks-logo-en-noslogan.svg Source: https://upload.wikimedia.org/wikipedia/commons/d/df/Wikibooks-logo-en-noslogan. svg License: CC BY-SA 3.0 Contributors: Own work Original artist: User:Bastique, User:Ramac et al. • File:Wikiquote-logo.svg Source: https://upload.wikimedia.org/wikipedia/commons/f/fa/Wikiquote-logo.svg License: Public domain Contributors: ? Original artist: ? • File:Wikiversity-logo.svg Source: https://upload.wikimedia.org/wikipedia/commons/9/91/Wikiversity-logo.svg License: CC BY-SA 3.0 Contributors: Snorky (optimized and cleaned up by verdy_p) Original artist: Snorky (optimized and cleaned up by verdy_p) • File:Wiktionary-logo-en.svg Source: https://upload.wikimedia.org/wikipedia/commons/f/f8/Wiktionary-logo-en.svg License: Public domain Contributors: Vector version of Image:Wiktionary-logo-en.png. Original artist: Vectorized by Fvasconcellos (talk · contribs), based on original logo tossed together by Brion Vibber

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