Upgrade of the LHC magnet interconnections thermal shielding

• Main Authors: Musso, Andrea, Barlow, Graeme, Bastard Alain, Charrondiere Maryline, Chrul Anna, Damianoglou Dimitrios, Deferne Guy, Dib Gaëlle, Duret, Max, Guinchard, Michael, Prin Hervé, Strychalski Michał, Craen Arnaud Vande, Villiger Gilles, Wright, Loren
• Format: Conference Proceeding
• Language: English
• Subjects: Aluminum; CERN LHC; Conduction cooling; CRYOSTATS; DESIGN; Dismantling; Electric bridges; FIRE HAZARDS; Gas tungsten arc welding; HELIUM; Insulation; Interconnections; Large Hadron Collider; Multilayers; Operators (mathematics); PARTICLE ACCELERATORS; Radiation shielding; Shields; SUPERCONDUCTING MAGNETS; THERMAL SHIELDS; Welding
• ISSN: 0094-243X; 1551-7616
• DOI: 10.1063/1.4860735

The about 1700 interconnections (ICs) between the Large Hadron Collider (LHC) superconducting magnets include thermal shielding at 50-75 K, providing continuity to the thermal shielding of the magnet cryostats to reduce the overall radiation heat loads to the 1.9 K helium bath of the magnets. The IC shield, made of aluminum, is conduction-cooled via a welded bridge to the thermal shield of the adjacent magnets which is actively cooled. TIG welding of these bridges made in the LHC tunnel at installation of the magnets induced a considerable risk of fire hazard due to the proximity of the multi-layer insulation of the magnet shields. A fire incident occurred in one of the machine sectors during machine installation, but fortunately with limited consequences thanks to prompt intervention of the operators. LHC is now undergoing a 2 years technical stop during which all magnet's ICs will have to be opened to consolidate the magnet electrical connections. The IC thermal shields will therefore have to be removed and re-installed after the work is completed. In order to eliminate the risk of fire hazard when re-welding, it has been decided to review the design of the IC shields, by replacing the welded bridges with a mechanical clamping which also preserves its thermal function. An additional advantage of this new solution is the ease in dismantling for maintenance, and eliminating weld-grinding operations at removal needing radioprotection measures because of material activation after long-term operation of the LHC. This paper describes the new design of the IC shields and in particular the theoretical and experimental validation of its thermal performance. Furthermore a status report of the on-going upgrade work in the LHC is given.