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Some of the technological applications of superconductivity include:- the production of sensitive magnetometers based on SQUIDs
- fast digital circuits (including those based on Josephson junctions and rapid single flux quantum technology),
- powerful superconducting electromagnets used in maglev trains, Magnetic Resonance Imaging (MRI) and Nuclear magnetic resonance (NMR) machines, magnetic confinement fusion reactors (e.g. tokamaks), and the beam-steering and focusing magnets used in particle accelerators
- low-loss power cables
- RF and microwave filters (e.g., for mobile phone base stations, as well as military ultra-sensitive/selective receivers)
- fast fault current limiters
- high sensitivity particle detectors, including the transition edge sensor, the superconducting bolometer, the superconducting tunnel junction detector, the kinetic inductance detector, and the superconducting nanowire single-photon detector
- railgun and coilgun magnets
- electric motors and generators[1]
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Magnetic Resonance Imaging (MRI) and Nuclear Magnetic Resonance (NMR)
The biggest application for superconductivity is in producing the large volume, stable, and high magnetic fields required for MRI and NMR. This represents a multi-billion US$ market for companies such as Oxford Instruments and Siemens. The magnets typically use low temperature superconductors (LTS) because high-temperature superconductors are not yet cheap enough to cost-effectively deliver the high, stable and large volume fields required, notwithstanding the need to cool LTS instruments to liquid helium temperatures. Superconductors are also used in high field scientific magnets.High-temperature superconductivity (HTS)
The commercial applications so far for high temperature superconductors (HTS) have been limited.HTS can superconduct at temperatures above the boiling point of liquid nitrogen, which makes them cheaper to cool than low temperature superconductors (LTS). However, the problem with HTS technology is that the currently known high temperature superconductors are brittle ceramics which are expensive to manufacture and not easily formed into wires or other useful shapes.[2] Therefore the applications for HTS have been where it has some other intrinsic advantage, e.g. in
- low thermal loss current leads for LTS devices (low thermal conductivity),
- RF and microwave filters (low resistance to RF), and
- increasingly in specialist scientific magnets, particularly where size and electricity consumption are critical (while HTS wire is much more expensive than LTS in these applications, this can be offset by the relative cost and convenience of cooling); the ability to ramp field is desired (the higher and wider range of HTS's operating temperature means faster changes in field can be managed); or cryogen free operation is desired (LTS generally requires liquid helium that is becoming more scarce and expensive).
HTS-based systems
HTS has application in scientific and industrial magnets, including use in NMR and MRI systems. Commercial systems are now available in each category.[3]Also one intrinsic attribute of HTS is that it can withstand much higher magnetic fields than LTS, so HTS at liquid helium temperatures are being explored for very high-field inserts inside LTS magnets.
Promising future industrial and commercial HTS applications include Induction heaters, transformers, fault current limiters, power storage, motors and generators, fusion reactors (see ITER) and magnetic levitation devices.
Early applications will be where the benefit of smaller size, lower weight or the ability to rapidly switch current (fault current limiters) outweighs the added cost. Longer-term as conductor price falls HTS systems should be competitive in a much wider range of applications on energy efficiency grounds alone. (For a relatively technical and US-centric view of state of play of HTS technology in power systems and the development status of Generation 2 conductor see Superconductivity for Electric Systems 2008 US DOE Annual Peer Review.)
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