Helium has become the quintessential substance and the most practical fluid in Cryogenics,
exhibiting properties as unique as superfluidity. Understanding helium properties is of paramount
importance to generate low-temperature environments capable of supporting superconductivity.
Hundred years after the first liquefaction of helium by Onnes, numerous fields, including medical imaging, energy storage, high‐energy physics (HEP), and thermonuclear fusion experiments, make use of high‐field superconducting magnets and
superconducting RF cavities cooled by Helium.Giant particle accelerators designed for HEP require large scale
cryogenic processes. A variety of cooling processes permit to operate linear accelerators and synchrotrons,
using two‐phase flows, supercritical or superfluid helium flows. The present talk will describe this fluid mysteries and review examples of large scale cryogenic applications
used at the European Organization for Nuclear Research (CERN) and at the Fermi National Accelerator Laboratory.