Mechanical Properties of the CMS Conductor

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 6 m diameter by 12.5 m long free bore, enclosed inside a 10000 ton return yoke. The magnetic field is achieved by a 4-layer superconducting solenoid made of a high purity aluminum (HPA) stabilized Rutherford type superconductor. The magnet is operated at 4.5 K, with a nominal current of 20 kA, for a total stored magnetic energy of 2.7 GJ. Due to the high magnetic forces at nominal field inside the winding pack, the structural component is the conductor itself to get a self-supporting winding structure. The mechanical reinforcement is made from aluminum alloy directly welded to the superconductor by Electron Beam (EB) welding technology before the winding operation. The external support cylinders also take part to the mechanical integrity.At each step of fabrication of the CMS conductor, the mechanical properties of the components and bonding between them are measured by destructive testing on short samples, in complement of continuous monitoring during production. This paper presents the results of the superconducting cable to pure aluminum shear testing, the tensile testing of the EN AW 6082 aluminum reinforcement, the insert to reinforcement shear testing, and the tensile testing of the full conductor before and after heat treatment induced during coil curing. Possible influence of the EB welding on the mechanical properties of the final conductor is investigated. Residual Resistivity Ratio (RRR) measurements of the HPA stabilizer are presented. Mechanical properties and equivalent RRR of the CMS conductor are presented for comparison with conductors of other geometry.

ILC Reference Design Report Volume 4 - Detectors

“…Another technical approach for the reinforcement has been made, in the CMS solenoid, by using a hybrid (or block) configuration, which consists of pure-aluminum stabilized superconductor and high strength aluminum alloy (A6082) blocks at both ends fixed by using electron-beam welding. The hybrid configuration is very useful and practical in large-scale conductors [105,106]. Based on these successful developments of both "uniform reinforcement" and "hybrid configuration" further improvement has been proposed, for future applications, in combining IV-98 ILC Reference Design Report these efforts [106,107] as summarized in Table 5.2, and shown in Figure 5.52.…”

“…The hybrid configuration is very useful and practical in large-scale conductors [105,106]. Based on these successful developments of both "uniform reinforcement" and "hybrid configuration" further improvement has been proposed, for future applications, in combining IV-98 ILC Reference Design Report these efforts [106,107] as summarized in Table 5.2, and shown in Figure 5.52. The central part of the CMS conductor partly composed of pure-aluminum stabilizer may be replaced by a Ni-doped high strength aluminum stabilizer developed for the ATLAS solenoid.…”

Status of the Construction of the CMS Magnet

“…Numerous studies and tests have been performed to understand what will be the yield and ultimate strengths of the conductor at 4.5 K after winding and final heat treatment during the impregnation process. The results taken on the overall section of the as-produced conductor, and , are significantly better than the design values and they are reported in [13]. …”

Experience Gained From the Construction, Test and Operation of the Large 4-T CMS Coil

“…The typical alloy EN AW-6082 has been selected for its high toughness, good extrudability and weldability. The underaged state (T51) allows winding to proceed with a not too stiff conductor, nevertheless resulting after the curing cycle to a T6 temper with further overall increase of the tensile yield strength, reaching at 4.2 K a of 400 MPa and a of 650 MPa, largely sufficient for the application [11], [12] (Fig. 4).…”