Superconductors function with almost no electrical resistance, making them useful for a variety of rapidly advancing technological applications. One common application is superconducting electromagnets, which utilize a series of superconducting coils to generate a magnetic field. Additionally, the electric power transmission system takes advantage of the low electrical resistance of superconductors to improve efficiency when transferring and storing electrical energy. Technological applications of superconductivity include:
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 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 electric motors and generators railgun and coilgun magnets fast fault current limiters low-loss power cables the production of sensitive magnetometers based on SQUIDs (superconducting quantum interference devices) fast digital circuits (including those based on Josephson junctions and rapid single flux quantum technology), RF and microwave filters (e.g., for mobile phone base stations, as well as military ultra-sensitive/selective receivers)
Low-temperature superconductivity
Magnetic resonance imaging and nuclear magnetic resonance The biggest application for superconductivity is in producing the large-volume, stable, and high-intensity magnetic fields required for magnetic resonance imaging (MRI) and nuclear magnetic resonance (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. As of 2023, there are some cryogen-free MRI magnets that operate within a safe temperature range for an LTS instrument. Rather than using a cryogen, such as liquid helium or nitrogen, that must be continually replenished, this design utilizes a GM cryocooler, which is a closed system containing helium gas. Through a combination of insulation techniques and a series of cooling stages, the GM cryocooler keeps the magnet at low enough temperatures without the additional cost of refilling a traditional cryogen. The design of this magnet uses superconducting coils to generate an electromagnetic field, which can be used to capture images of the human body. However, unlike a typical MRI magnet, this design is unable to continue functioning as long as a typical cryogen-based MRI magnet in the event of a power outage.
Particle accelerators Because of their low electrical resistance, superconductors are more efficient at producing electromagnetic fields than typical conductors, making them a cost-effective choice for use in physics research. In the first LTS particle accelerators, Nb-Ti was the preferred superconductor because of its ductility and ability to carry a considerable amount of electric current. However, future research is planned regarding the possibility of replacing Nb-Ti with niobium-tin, which is able to carry a greater current but is also more brittle. By overcoming the challenge of designing coils from a brittle material such as Nb-Ti, researchers may be able to develop a more efficient superconducting particle accelerator. Particle accelerators such as the Large Hadron Collider can include many high field electromagnets requiring large quantities of LTS. To construct the LHC magnets required more than 28 percent of the world's niobium-titanium wire production for five years, with large quantities of NbTi also used in the magnets for the LHC's huge experiment detectors.
Magnetic fusion devices During fusion processes, electromagnets can be used to contain plasma. Superconducting electromagnets produce stronger magnetic fields from a lower energy input than their traditional counterparts but also involve higher initial costs. Conventional fusion machines (JET, ST-40, NTSX-U and MAST) use blocks of copper. This limits their fields to 1-3 Tesla. Several superconducting fusion machines are planned for the 2024-2026 timeframe. These include ITER, ARC and the next version of ST-40. The addition of high-temperature superconductors should yield an order of magnitude improvement in fields (10-13 tesla) for a new generation of Tokamaks. The cable-in-conduit (CIC) design for superconductors is also commonly utilized for electromagnetic confinement. The CIC conductor is able to withstand large amounts of force, is efficient at transferring electrical current, and is a good insulator, making it well-suited for use in fusion processes.
Generators Superconducting wires and electromagnetic fields generated from superconducting coils can be utilized in some generators. Superconducting versions of these elements are more efficient than their counterparts, allowing for greater electricity generation from a smaller and lighter generator. The superconducting coils in these generators are typically made from NbTi and are used to generate an electromagnetic field. Since NbTi is a LTS, liquid helium is typically used as a cryogen to keep the generator at a cool enough temperature. This type of superconducting generator has been applied to power offshore wind turbines since the design optimizes energy output from a relatively small and lightweight generator.
Superconducting electromagnet iron separator (SEIS) In coal purification, electromagnets are employed to remove ferromagnetic substances, primarily iron, from coal. Superconductors are more energy-efficient than typical conductors, so they are used to create superconducting coils that generate an electromagnetic field. These LTS coils require cryogenic cooling from liquid helium to safely operate. These superconducting magnets require less energy input and take up a smaller volume than a typical magnet.
High-temperature superconductivity
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