Commissioning of the CMS Magnet

CMS (Compact Muon Solenoid) is one of the large experiments for the LHC at CERN. The superconducting magnet for CMS has been designed to reach a 4 T field in a free bore of 6 m diameter and 12.5 m length with a stored energy of 2.6 GJ at full current. The flux is returned through a 10 000 t yoke comprising of five wheels and two end caps composed of three disks each. The magnet was designed to be assembled and tested in a surface hall, prior to be lowered at 90 m below ground, to its final position in the experimental cavern. The distinctive feature of the cold mass is the four-layer winding, made from a reinforced and stabilized NbTi conductor. The design and construction was carried out by CMS participating institutes through technical and contractual endeavors. Among them CEA Saclay, INFN Genova, ETH Zurich, Fermilab, ITEP Moscow, University of Wisconsin and CERN. The construction of the CMS Magnet, and of the coil in particular, has been completed last year. The magnet has just been powered to full field achieving electrical commissioning. After a brief reminder of the design and construction the first results of the commissioning are reported in this paper

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CMS coil thermal shields final design

The Compact Muon Solenoid (CMS) is one of the detectors that is under construction in the framework of the Large Hadron Collider (LHC) project at CERN. The design field of the CMS magnet is 4 T in a 6 m diameter and 12.5 m long bore leading to a stored energy of 2.7 GJ. The coil cryogenic system is designed to cool the thermal shields by helium gas at 60 K and protect the cold mass at 4.5 K from the thermal radiation. The thermal shield design must take into account cryogenics, eddy currents, mechanical and realization considerations. This paper presents a detailed analysis of the eddy currents induced in the thermal shield, using a variational formulation of the problem in terms of the electric vector potential and a finite element method. The thermal and mechanical design are then described. (5 refs)