Structural Analysis of an Integrated Model of Short Straight Section, Service Module, Jumper Connection and Magnet Interconnects for the Large Hadron Collider

The Short Straight Section (SSS) of the Large Hadron Collider (LHC) may undergo relative displacements between cold-mass and cryostat for the following three reasons: - Fabrication tolerance of interconnection bellows - Global smoothing after pre-alignment - Ground motion in a sector of the LHC tunnel The forces responsible for such displacements stem from finite stiffness of interconnect bellows & metal hoses of the internal piping of the jumper connection and from relatively flexible 'glass fibre reinforced epoxy' (GFRE) composite supports of the cold mass. In addition, the vacuum jacket of the jumper connection and the large sleeves attached to both ends of SSS produce elastic deformations of the cryostat vessel. A unified finite element model consisting of cryostat, large sleeves, vacuum jacket of jumper, interconnection bellows, internal piping of jumper, composite cold supports and alignment jacks has been prepared. The knowledge of the position of the cold mass with respect to its cryostat under various conditions of alignment done using external fiducials mounted on the cryostat is essential. The maximum relative displacement for satisfactory machine operation is 0.1 mm. An SSS with cryogenic jumper connection has been modelled with the aim of assessing this possible displacement.