Magnet System

The magnet system for ATLAS consists of four superconducting magnets: the Central Solenoid (CS), and the Barrel Toroid (BT) and two End-Cap Toroids (ECT) that generate the toroidal field of about 1T.

The Central Solenoid generates a 2T field with a current of 7600 A in the superconducting cable. The 5.3 m long coil has an inner radius of 1.2 m. It is a layer coil made of a doped Al stabilized NbTi/Cu rectangular conductor wound on its thin edge inside a 12 mm thin Al support cylinder. It is integrated in the liquid argon cryostat. It was tested up to 8100 A.

The End-Cap Toroids consist each of 5 × 5m2 coil modules madeof 41×12mm2 NbTi/Cu conductor, interlinked by eight so called keystone boxes, see figure below. The castellated shape of the end-cap cryostat makes it possible to rotate the ECTs by 22.5° with respect to the Barrel Toroid. Since the magnetic windings overlap, the ECT is pulled towards the Barrel Toroid with a force going up to about 300 tons.

The Barrel Toroid has eight racetrack coils of 25 × 5m2 size. Thecoils are kept in place by an inner and an outer set of eight rings of struts positioned along the coils. The assembled toroid is resting on 18 feet connected to the floor of the cavern. The coils are wound from 57×12mm2 NbTi/Cu conductor. They have been tested up to a current of 22 kA