Liquid Helium – The Coldest Liquid on Earth
The boiling point of helium is 4.2 K or -269 °C. Liquid helium is the coldest liquid on earth. It is mainly used as coolant to reach extremely low temperatures. In order to limit product losses, liquid helium is supplied and stored in special cryogenic vessels, so-called dewars. According to the actual demand, Messer offers liquid helium in dewars of different sizes, which range from 50 liters to dewars with a capacity of up to 450 liters. Very large consumers, such as equipment manufactures or major research institutes, may also be supplied by tank containers with a capacity of 40,000 liters.
Applications of Liquid Helium
Most technical applications of liquid helium are related to superconductivity. This is the physical property observed in certain materials that if the material is cooled down below a “critical” temperature, the electrical resistance vanishes. Due to the extremely low transition temperatures of technically used superconductors, they need to be cooled by liquid helium. The most important application of superconductivity is in very powerful superconducting electromagnets. By far the largest applications of liquid helium is the use in magnetic resonance imaging (MRI) and nuclear magnetic romance (NMR) machines, followed by beam-steering magnets used in particle accelerators.
Liquid Helium for Magnetic Resonance Imaging (MRI)
Magnetic resonance imaging (MRI) is a medicinal imaging technique. The MRI scanners use strong magnetic fields, generated by a superconducting magnet. Liquid helium cools the magnet below the critical temperature of the superconducting solenoid coil.
Liquid Helium for Nuclear magnetic resonance spectrometry (NMR)
Nuclear magnetic resonance (NMR) spectroscopy is a technique used to identify and analyze the structure of molecules. The samples are placed in a strong magnetic field, which is generated by a superconducting magnet. Liquid helium is used to cool the magnet so it remains below the critical temperature of the superconducting solenoid coil.
