Consolidation of the 13 kA Interconnects in the LHC for Operation at 7 TeV

• Published in: IEEE transactions on applied superconductivity Vol. 21; no. 3; pp. 2376 - 2379
• Main Authors: Verweij, A P, Bertinelli, F, Lasheras, N, Charifoulline, Z, Denz, R, Fessia, P, Garion, C, ten Kate, Herman H J, Koratzinos, M, Mathot, S, Perin, A, Scheuerlein, C, Sgobba, S, Steckert, J, Tock, J.-P, Willering, G P
• Format: Journal Article Conference Proceeding
• Language: English
• Published: New York, NY IEEE 01.06.2011; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Busbars; Copper; Current measurement; Cyclic accelerators and storage rings; Design. Technologies. Operation analysis. Testing; Electrical engineering. Electrical power engineering; Electrical resistance measurement; Electromagnets; Electronics; Exact sciences and technology; Experimental methods and instrumentation for elementary-particle and nuclear physics; Integrated circuits; interconnections; Joints; Large Hadron Collider; Nuclear physics; Physics; Resistance; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Soldering; Superconducting magnets; Various equipment and components; CERN LHC; Shunt; Busbars; Magnet; interconnections; soldering; resistance; Integrated circuit bonding; Dipole circuit; Busbar; Interconnection; Soldered joint; Integrated circuit
• DOI: 10.1109/TASC.2010.2083622
• ISSN: 1051-8223

The accident in the LHC in September 2008 occurred in an interconnection between two magnets of the 13 kA dipole circuit. Successive measurements of the resistance of other interconnects revealed other defective joints, even though the SC cables were properly connected. These defective joints are characterized by a poor bonding between the SC cable and the copper stabilizer in combination with an electrical discontinuity in the copper stabilizer. A quench at the 7-13 kA level in such a joint can lead to a fast and unprotected thermal run-away and hence opening of the circuit. It has therefore been decided to operate the LHC at a reduced and safe current of 6 kA corresponding to 3.5 TeV beam energy until all defective joints are repaired. A task force is reviewing the status of all electrical joints in the magnet circuits and preparing for the necessary repairs. The principle solution is to resolder the worst defective joints and, in addition, to apply an electrical shunt made of copper across all joints with sufficient cross-section to guarantee safe 12-13 kA operation at 7-7.5 TeV. In this paper the various actions that have lead to this solution are presented.