Development of large-capacity refrigeration at 1.8 K for the Large Hadron Collider at CERN

CERN, the European Laboratory for Particle Physics, is working towards the construction of the Large Hadron Collider (LHC), a high-energy, high-luminosity particle accelerator and collider [1] of 26.7 km circumference, due to start producing frontier physics, by bringing into collision intense proton and ion beams with centre-of-mass energies in the TeV-per-constituent range, at the beginning of the next century. The key technology for achieving this ambitious scientific goal at economically acceptable cost is the use of high-field superconducting magnets using Nb-Ti conductor operating in superfluid helium [2]. To maintain the some 25 km of bending and focusing magnets at their operating temperature of 1.9 K, the LHC cryogenic system will have to produce an unprecedented total refrigeration capacity of about 20 kW at 1.8 K, in eight cryogenic plants distributed around the machine circumference [3]. This has requested the undertaking of an industrial development programme, in the form of a collaboration between CERN and CEA, France, for investigating specific machinery, i.e. very-low pressure cryogenic heat exchangers, volumetric and hydrodynamic compressors, as well as practical and efficient thermodynamic cycles. We report on the aims lines of action and present progress of this ongoing programme.