Dynamic Stresses in the LHC TCDS Diluter from 7 TeV Beam Loading

In the event of an unsynchronised beam abort, the MSD extraction septum of the LHC beam dumping system is protected from damage by the TCDS diluter. The simultaneous constraints of obtaining sufficient beam dilution while ensuring the survival of the TCDS make the design difficult, with high thermally induced dynamic stresses occurring in the material needed to attenuate the particle showers induced by the primary beam impact. In this paper, full 3D simulations are described where the worst-case beam loading has been used to generate the local temperature rise and to follow the resulting time evolution of the mechanical stresses. The results and the accompanying design changes for the TCDS, to provide an adequate performance margin, are detailed.