Conceptual Design of the CMS 4 Tesla Solenoid

The detection of new physics signals at the highest luminosities available in proton-proton collisions at LHC requires identification and precise measurement of muons, photons and electrons. Toroidal and solenoidal fields were considered at the beginning of the design. For the CMS detector, the choice of a compact design led to the choice of a strong magnetic field. The most practical magnet that can generate a strong magnetic field is a solenoid. A long (about 13 m) superconducting solenoid of large radius generating a magnetic field of 4 T guarantees good momentum resolution. The magnetic flux is returned via a 1.8 m thick iron yoke of a weight of 12 000 tonnes. The magnetic stored energy is 2.52 GJ and the coil total weight is 500 tonnes. The coil main design features are indirect cooling, pure aluminium stabilisation and mechanically reinforced conductor. It is a four layer winding, composed of 4 axial sections bolted together.