Why is helium used in cryogenics?

Helium is used in cryogenics because of its extremely low boiling point, making it ideal for achieving ultra-low temperatures.

Helium is a unique element with some very special properties that make it ideal for use in cryogenics. Cryogenics is the science of producing and managing extremely low temperatures, typically below -150 degrees Celsius. The key to achieving these temperatures is the use of substances that remain liquid at very low temperatures, known as cryogenic fluids.

Helium is one such fluid. It has the lowest boiling point of any element, at -268.93 degrees Celsius, just a few degrees above absolute zero (-273.15 degrees Celsius). This means that helium can be used to cool objects to temperatures close to absolute zero, which is essential in many areas of scientific research.

In addition to its low boiling point, helium has other properties that make it useful in cryogenics. It is chemically inert, meaning it does not react with other substances. This is important because it means that helium can be used to cool sensitive equipment without risk of chemical reactions that could damage the equipment.

Furthermore, helium has a very low viscosity, even at ultra-low temperatures. This means it can flow easily, allowing it to effectively transfer heat away from the object being cooled. It also has a high thermal conductivity, which means it can absorb a lot of heat, further enhancing its cooling capabilities.

Finally, helium is relatively abundant and easy to obtain, making it a practical choice for use in cryogenics. It is extracted from natural gas deposits, where it is produced by the radioactive decay of heavy elements in the Earth's crust.

In summary, helium's extremely low boiling point, chemical inertness, low viscosity, high thermal conductivity, and availability make it the ideal choice for use in cryogenics.