ATLAS solenoid operates underground

A new phase for the ATLAS collaboration started with the first operation of a completed sub-system: the Central Solenoid.

The solenoid was cooled down to 4.5 K from 17 to 23 May. The first current was established the same evening that the solenoid became cold and superconductive. 'This makes the ATLAS Central Solenoid the very first cold and superconducting magnet to be operated in the LHC underground areas!', said Takahiko Kondo, professor at KEK.

Though the current was limited to 1 kA, the cool-down and powering of the solenoid was a major milestone for all of the control, cryogenic, power and vacuum systems-a milestone reached by the hard work and many long evenings invested by various teams from ATLAS, all of CERN's departments and several large and small companies.

Since the Central Solenoid and the barrel liquid argon (LAr) calorimeter share the same cryostat vacuum vessel, this achievement was only possible in perfect collaboration with the LAr cryogenic team. The helium liquifer used previously at CERN has been combined with the new shield refrigerator in order to cool all of the ATLAS magnets, including the giant ATLAS superconducting toroid coils, which are about to be cooled down. Powering up the solenoid to the nominal operating current of 7.6 kA has to wait until the end-cap liquid argon calorimeters have been put in place during the coming months. The solenoid and its proximity cryogenic components and controls were proposed, designed and manufactured by KEK in Japan in close collaboration with CERN.