A heavy load arrives for ALICE

1 November 2003

On 25 September the two large coils for the ALICE dipole magnet arrived at Point 2 of the Large Hadron Collider (LHC) after a 1200 km journey from their manufacturer. The two coils, which are 5 m long, 6 m wide, more than 3 m high, and weigh 20 tonnes each, were manufactured by Sigmaphi in Vannes, France. They will form the dipole magnet of the forward muon arm spectrometer of the ALICE detector.

Even loading the huge coils at Sigmaphi was not a simple task. The overhead crane could not be used to lift the coils plus their supports, so the coils had to be jacked up on rollers and pulled outside the hall, where a mobile crane lifted them onto the trucks. Moreover, the big door of the assembly hall was too small and part of the wall had to be cut open to roll out the coils. Once on the road, detours were necessary because of the height of bridges and so on.

The two coils will be installed within a 780 tonne iron yoke, which has been manufactured in Russia and is on its way to CERN. The dipole magnet will be used to identify high-momentum muon pairs and will be one of the biggest dipoles operating at room temperature. The impressive size and gap width between the poles of 3-4 m is necessary to obtain the required acceptance angle of 9°. The electrical power dissipation will be close to 4 MW, and to reach the nominal field of 0.7 T, it will be powered by a DC power converter providing 6000 A.

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