CERN inaugurates LHC cryogenics
The beginning of June saw the start of a new phase at the LHC project, with the inauguration of LHC cryogenics. This was marked with a symposium in the Globe of Science and Innovation attended by 178 representatives of the research institutes involved and industrial partners. It also coincided with the stable low-temperature operation of the cryogenic plant for sector 7-8, the first sector to be cooled down (CERN Courier May 2007 p5).
The LHC and its large particle detectors make intensive use of superconducting magnets and cryogenics. The LHC helium cryogenic system is the largest and most complex ever built, with more than 160 kW equivalent at 4.5 K and 20 kW at 1.8 K (CERN Courier May 2004 p15). Cryogenic systems are 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 (CERN Courier December 2005 p28).
The system for the LHC involves many industrial-scale devices, where reliability is of paramount importance. The LHC's energy of 7 TeV requires a strong magnetic field, which is provided by niobium-titanium coils operating at 1.9 K. Besides enhancing the performance of the niobium-titanium superconductor, this temperature regime makes use of the excellent heat-transfer properties of helium in its superfluid state. The design for the LHC cryogenics had to incorporate both newly ordered and reused 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.
The main elements for both the accelerator and the detectors are now operational. The large superconducting magnets and liquid argon calorimeters for the ATLAS and CMS experiments have been cooled and tested, and all superconducting magnets for the accelerator have been procured from industry, cold tested at CERN and installed in the ring. The first 3.3 km sector of the machine – one-eighth of the circumference – has been cooled down and tested, permitting the full-scale validation of basic design choices. In particular, thanks to the superfluid helium cooling system, the magnet temperature could be controlled to within 0.1 K over the sector length. The results were recently reported at the CEC 2007 conference in Chattanooga, Tennessee. Although the commissioning work is far from finished, the cyrogenics groups at CERN felt that after 10 years of construction it was now a good time to celebrate, organizing the Symposium for the Inauguration of LHC Cryogenics that took place on 31 May – 1 June at CERN's Globe of Science and Innovation. After an inaugural address by CERN's director-general, Robert Aymar, the programme included 21 presentations of the different aspects of the system, an industrial exhibition by seven companies, and visits to technical sites above and below ground.
The symposium brought together specialists from industry, participating institutes and CERN, all involved in the design and construction of the LHC cryogenic system. Some 20 general and scientific journalists also attended. The event culminated with the formal inauguration and ribbon-cutting by the LHC project leader Lyn Evans and a final buffet. The event was co-sponsored by Air Liquide DTA (France), ISQ (Portugal) and Linde Kryotechnik AG (Switzerland).
• The programme for the symposium can be found at http://indico.cern.ch/internalPage.py?pageId=3&confId=9046.