The Construction of the Modules Composing the CMS Superconducting Coil

Abstract

Abstract-CMS (Compact Muon Solenoid) is a general-purpose detector designed to run at the highest luminosity at the CERN Large Hadron Collider (LHC). Its distinctive features include a 4 T superconducting solenoid with a 6 m diameter by 12.5 m long free bore, enclosed inside a 10,000-ton return yoke. The construction of the five modules composing the coil is presently under way. The methods for constructing large aluminum alloy mandrels, for winding the reinforced conductor with high accuracy of the winding pack and for impregnating the single large modules (50 t) have been assessed through the construction of a module prototype. The prototype has the same radius as a CMS module (6900 mm outer diameter), but a shorter axial length (670 mm against 2500 for the module). The relevant technological result was the understanding of the methods for obtaining a large coil with a very limited shape deformation ( 2.5 mm on diameter) for allowing the precise mounting of the modules. This paper describes the main technical issues of the prototype and of the construction of the first modules, the geometrical and RT tests performed on them and the common problems related to the series construction of large superconducting coils.

Mechanical Properties of the CMS Conductor

“…The reinforcement resistivity is higher by a factor 1000 compared to the HPA at 5 T and at 4.2 K, consequently the influence of the reinforcement resistivity on is lower than 1%, so the following simplified relationship is obtained: (2) where is the aluminum alloy cross-sectional ratio expressed in percent of the total conductor cross section.…”

“…The CMS magnet main features are a 12.5 m magnetic length, with a 6.36 m diameter aperture, indirectly cooled down and operated at 4.5 K. The magnet is built by winding five modules with four layers of reinforced superconductor, inside a 50 mm thick external cylinder [2]. The 20 kA superconductor consists of a superconducting Rutherford type cable stabilized with High Purity Aluminum (HPA), and mechanically reinforced with two continuous sections of aluminum alloy [3] welded by Electron Beam (EB) technology [4].…”

Commissioning of the CMS Magnet

“…As pointed out in previous papers [3], [4] the CMS solenoid presents three new features with respect to previous detector magnets: -Due to the high ampere-turns required for generating a field of 4 T (46.5 MA), the winding is composed of four layers, instead of the usual one (as in the Aleph or Delphi coils) or maximum two layers (as in ZEUS coil). -The standard conductor, made from a Rutherford cable co-extruded with pure aluminium, is mechanically reinforced with aluminium alloy.…”

“…Furthermore a dedicated fully 1051-8223/$25.00 © 2007 IEEE automated device was developed for a precise positioning of the turns into the winding [4].…”

Status of the Construction of the CMS Magnet

“…Mechanical work is progressing on the two remaining mandrels. Detailed analysis of the module construction and winding is reported in [14].…”