Reliability oriented optimisation of the magnet interconnects in the LHC

by C. Garion

Thursday 20 Jun 2002, 14:15 → 15:15 Europe/Zurich

LHC Auditorium (CERN)

To achieve the maximum beam energy in the LHC, the accumulated length of spatial zones dedicated to the interconnections between the main cryo-magnets has been limited to 3 % of the total magnetic length in the Arcs and Dispersion Suppressors. Such a low ratio leads to a very compact design of systems and sub-systems situated in the LHC interconnections. The requirements concerning reliability of the LHC interconnections are very tight since the availability of the collider for physics cannot be compromised. One of the most important systems housed in the LHC interconnections is the thermal contraction/expansion compensation system (bellows expansion joints). In order to cope with the space limitations a deliberate choice, supported by a mathematical optimisation, was made and the LHC bellows expansion joints work in highly inelastic regime called the low-cycle fatigue. All deformation developed during cool-down and warm-up of the collider is localised in the interconnections (the accumulated value of thermal contraction approaches 70 m for LHC Arcs and DS). The failure modes, related to the response of the compensation system at cryogenic temperatures, are grouped into three categories: material failures (micro-damage and phase transformations), structural failures (instability modes) and fatigue failures (low cycle fatigue). All the above listed phenomena, which influence the reliability of the LHC interconnections, are analysed and evaluated.

Note: The seminar will be given in French