A word from the DG: A cryogenic success

The beginning of this month saw the start of a new phase in the LHC project, with its first inauguration, for the LHC cryogenics. This was marked with a symposium in the Globe attended by 178 representatives of the industrial partners and research institutes involved. It also coincided with stable low-temperature operation of the cryogenic plant for sector 7-8, the first sector of the LHC to be cooled down. A look at the LHC web site (http://lhc.web.cern.ch/lhc/) shows this steady operation.

The cryogenic system for the LHC is the largest and most complex ever built, involving many large devices on an industrial scale, where reliability is of paramount importance. The LHC’s energy of 7 TeV required a high magnetic field provided by niobium-titanium coils operating at 1.9 K. This is a new temperature regime for large-scale cryogenics, chosen to make use of the excellent heat-transfer properties of helium in its superfluid state. The final design for the LHC cryogenics had to incorporate both newly ordered and re-used refrigeration plant from LEP operating at 4.5 K, together with a second stage operating at 1.9 K, in a system that could be replicated around the LHC. Cryogenic systems are also important for both the ATLAS and CMS detectors, which use different technologies with helium and argon required for their superconducting magnet systems and for the ATLAS calorimeter.

With the stable operation of the LHC cryogenics for sector 7-8, work has begun on electrical tests. These have involved checking the insulation, continuity etc, before powering up, which is now underway. At the same time, work continues to resolve the problem that was found in March with the inner triplet magnets. The solution proposed to sustain the longitudinal forces generated in the pressure tests is being tested in a set of magnets on the surface. If it proves to work as expected then it will be implemented on other inner triplets in situ underground.

This additional work will be taken into account when the new proposal for the LHC schedule is presented to Council in the week beginning 18 June. I will let you know the conclusions from this meeting when I talk to you on 27 June. Our essential physics goal for the LHC, however, remains to reach a good integrated luminosity – of 1 fb^-1 or more – during 2008.

Robert Aymar