Superconducting magnet refers to a general term for superconducting coils and their cryogenic containers. The superconducting magnet is the most important core component of the superconducting suspension railway. The propulsion, suspension and guiding force of the vehicle are all generated by the superconducting coil. Like permanent magnets, superconducting magnets can provide a stable magnetic field, and superconducting magnets can also provide high-intensity magnetic fields that ordinary permanent magnets cannot provide, which is why maglev railways use superconducting magnets. Due to the development of high-temperature superconductors, superconductivity occurs at liquid nitrogen temperature (78K), which greatly improves the performance of superconducting materials. However, as the superconducting material used in the maglev railway, the critical current of the high-temperature superconducting material under the high-intensity magnetic field cannot meet the requirements.
China came out
At 8:00 on September 19, 2007, the Beijing Spectrometer superconducting magnet of the large particle detector of the Beijing Electron Positron Collider Major Reconstruction Project (BEPCⅡ) successfully reached 10,000 Gauss (20,000 times the Earth’s magnetic field), and the current reached 3368 amps, the maximum energy storage reaches 10 million joules, which has reached the design target. The superconducting magnet was independently developed by the Institute of High Energy Physics, Chinese Academy of Sciences. It is one of the key components of the Beijing Spectrometer, mainly including superconducting coils, cryostats, cold substances and electromagnetic force suspension support structures and valve boxes.
Making superconducting magnets is not just a matter of magnetic materials. It is difficult to explain this aspect clearly in a short article. Since the content of this aspect is very meaningful in magnetic applications, it is specially explained briefly. Obtaining a flux density above 2 (Tesla) (a magnetic field of 1.6X10′ Amp/m) is rather difficult with an electromagnet with an iron core. If a hollow solenoid with a superconducting coil is used, a high magnetic flux density of about 3~15 (Tesla) can be obtained. This device is mainly used in research work, such as hydrogen cloud chamber, MHD power generation, electron microscope , nuclear magnetic resonance, closed plasma (nuclear fusion power generation) and so on. If the train reaches a speed of 500 kilometers per hour, the method of magnetic levitation can be used to suspend the train off the ground. As long as it is driven once, the train can move forward continuously. The key to realizing this scheme is to use superconducting magnets.
(1) The current transmission resistance in the coil of the superconducting magnet is zero, and it can conduct strong currents that cannot be conducted by ordinary wires;
(2) It can generate a strong magnetic field of up to ten Tesla, which is extremely beneficial to greatly improve the sensitivity and resolution of the nuclear magnetic resonance spectrometer. At the same time, the uniformity and stability of the magnetic field are also very good, which is ideal for modern spectrometers. magnet;  (3) The field strength is high and stable and uniform. At present, the superconducting magnet spectrometer is generally around 200N~00MG, and the maximum can reach 600MG.