Mechanical Design for Robustness of the LHC Collimators

The functional specification of the LHC Collimators requires, for the start-up of the machine and the initial luminosity runs (Phase 1), a collimation system with maximum robustness against abnormal beam operating conditions. The most severe cases to be considered in the mechanical design are the asynchronous beam dump at 7TeV and the 450GeV injection error. To ensure that the collimator jaws survive such accident scenarios, low-Z materials were chosen, driving the design towards Graphite or Carbon reinforced Carbon composites. Furthermore, in-depth thermo-mechanical simulations, both static and dynamic, were necessary. This paper presents the results of the numerical analyses performed for the 450GeV accident case, along with the experimental results of the tests conducted on a collimator prototype in CERN TT40 transfer line, impacted by a 450GeV beam of 3.2e13 protons, with impact transverse offsets from 1 to 5 mm.