The principle of superconducting magnet is to use the complete diamagnetism (Messner effect) of superconductor: after entering superconducting state, the magnetic flux lines of external magnetic field will be discharged from the superconductor, so when the magnet approaches the superconductor, it will be strongly repelled, and superconducting magnetic levitation will be realized when the repulsion and gravity cancel.
when applying superconducting materials, if one or more superconducting coils are used to form a device for generating magnetic fields, ordinary superconducting materials are easily affected by magnetic fields and lose superconductivity, so it seems that superconductivity and magnetism cannot be taken into account at the same time. This problem was not solved until the superconductivity of niobium zirconium, niobium titanium and niobium tristin compound materials was discovered in the 196s. Superconducting magnets are such superconductors that keep their magnetism.
Superconducting magnet will not lose energy when it runs under the condition of direct current, and it can generate a huge magnetic field through a strong current. In addition, it has stable magnetism, high uniformity of magnetic field in space, small volume and light weight, so it is widely used. It has important practical functions and great application prospects in the fields of electrician, transportation, medical care, military industry and scientific experiments, and some of them have achieved practical benefits.
At present, magnetic resonance imaging equipment with superconducting magnets has become one of the most popular clinical diagnostic equipment in hospitals, and thousands of magnetic resonance imaging equipment have been used in hospitals all over the world. In addition, scientific instruments such as superconducting nuclear magnetic resonance spectrometer have also become commodities and been widely used.