Last cast for the LHC

The first major contract signed for the LHC is drawing to a close. Belgian firm Cockerill Sambre (a member of the Arcelor Group) has just completed production of 50,000 tonnes of steel sheets for the accelerator's superconducting magnet yokes, in what has proved to be an exemplary partnership with CERN.


Philippe Lebrun, Head of the AT Department, Lyn Evans, LHC Project Leader, and Lucio Rossi, Head of the AT-MAS Group, in front of the last batch of steel for the LHC at Cockerill Sambre.

It was a bright red-letter day at the end of May, when Belgian firm Cockerill Sambre of the Arcelor Group marked the completion of one of the largest contracts for the LHC machine by casting the last batch of steel sheets for the LHC superconducting magnet yokes in the presence of LHC Project Leader Lyn Evans, AT Department Head Philippe Lebrun, Magnets and Superconductors (AT-MAS) Group Leader Lucio Rossi and Head of the AT-MAS Group's components centre Francesco Bertinelli. The yokes constitute approximately 80% of the accelerator's weight and, if placed side by side, would stretch over 20 km !

The end of this production run carried special symbolic value as it was the first major contract to be concluded for the LHC machine. "It was a 60 million Swiss franc contract, signed just after the CERN Council approved the LHC project in December 1996," recalls Lucio Rossi.

Cockerill Sambre have supplied 50,000 tonnes of low-carbon steel sheets, which are sent on to another supplier for fine-blanking. Once the components have been fine-blanked and aligned side by side they form the magnet yokes.

The steel was specially developed for CERN's purposes. The sheets were substantially thicker than conventional steel sheets. "Cockerill Sambre managed to produce 5.8 mm thick sheets with excellent magnetic properties," says Lucio Rossi. This exceptional thickness was specified in order to limit the number of fine-blanking operations and, thus, the cost and lead times for both the yoke production and the magnet assembly. In addition, a special treatment process was developed, involving the light oxidation of the sheets at the time of production, in order to prevent corrosion and magnetic coupling. This inexpensive process generated millions of francs' worth of savings because it obviated the need for post-production treatment, which would have been far more expensive. Rossi adds "in the intervening period, Cockerill Sambre have found other commercial applications for this special steel developed for CERN."

Furthermore, in view of the need to obtain sheets of identical grade, CERN opted to entrust the whole contract to a single supplier, and this makes Cockerill Sambre's performance all the more praiseworthy. The firm showed admirable reliability throughout and agreed, for instance, to work with CERN's own control instruments. In 2002, they were awarded the first "Golden Hadron" prize, official recognition that they are among the LHC project's top suppliers.

Several other major contracts are reaching completion, a sure sign that we are entering the final phase of machine construction - production has recently been completed of the 60 km of vacuum pipes in which the LHC beams will circulate. These exceptional 16-m long pipes, made from austenitic steel, had to be continuously extruded and comprise not a single weld in order to ensure perfect leaktightness between the vacuum inside and the superfluid helium outside. This was another challenge taken up by a single firm - DMV of Bergamo, Italy - and there too, the partnership with CERN has been a resounding success.