The LHC Incident in Sector 3–4: A Simplified Mechanical Model to Explain the Mechanical Damages

On the 19th of September 2008 during powering tests of the LHC main dipole circuit in sector 3-4 an electrical fault occurred. A part of the most important resulting damages were caused by the displacements of cryostated cold masses due to the effect of an over pressurization in the insulation vacuum enclosure. The relative displacement of the interconnected units was resulting in mechanical and electrical damages. Main objects concerned were the mechanical interconnect and the magnet bus bar system. Furthermore electrical arcs induced open breaches in the helium enclosure. In this paper a simplified dynamic numerical model is described to reproduce the observed mechanical defects. In addition the analysis indicates that only a few parameters are dominating the physical quantities in this very complex event.