samedi 20 décembre 2014

CERN - LHC filling with liquid helium at 4 kelvin

CERN - European Organization for Nuclear Research logo.

December 20, 2014

CERN gears up to cool LHC down

Last week the cryogenics team at CERN finished filling the arc sections of the Large Hadron Collider (LHC) with liquid helium. The helium, which is injected into magnets that steer particle beams around the 27-kilometre accelerator, cools the machine to below 4 degrees kelvin (-269.15°C).

The process of filling the LHC is an important milestone on the road to restarting the accelerator at higher energy, though it will still take many weeks to cool the entire accelerator to its nominal operating temperature of 1.9 K (-271.3°C).

The electromagnets that steer particle beams around the LHC must be kept cold enough to operate in a superconducting state – the temperature at which electricity can pass through a material without losing energy to resistance. The niobium-titanium wires that form the coils of the LHC’s superconducting magnets are therefore maintained at 1.9 K by a closed liquid-helium circuit. This is colder than the average temperature – 2.7 K – in outer space.

Large Hadron Collider (LHC)

Some 1292 dipole magnets will produce a magnetic field of 8.33 tesla to keep particle beams on course around the LHC's 27-kilometre ring. A current of 11,850 amps in the magnet coils is needed to reach magnetic fields of this amplitude. The use of superconducting materials has proved to be the best – and most cost-effective – way to avoid overheating the coils.


CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.

The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.

Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 20 Member States.

Related link:

Large Hadron Collider (LHC):

Find out more:

Cryogenics at the LHC:

About the higher energy restart:

Image, Text, Credits: CERN/Cian O'Luanaigh/Video: Noemi Caraban Gonzalez.


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