Mechanical dynamic analysis of the LHC arc cryo-magnets

The arcs of the Large Hadron Collider (LHC) will contain around 1700 main superconducting dipoles and quadrupoles. The long and heavy magnets are placed on fragile composite support posts inside a cryostat to reduce the heat in-leak to the magnets super fluid helium bath. The presence of such fragile components like the support posts, the beam position monitors and the corrector magnets make the cryo-magnets very difficult to handle and transport. Furthermore, keeping the geometry of the cryo-magnets unchanged (in the range of 0.1 mm) throughout the various transports and handling is essential for the good functioning of the future LHC. A detailed dynamic analysis was performed to determine the behavior of the cryo-magnets under all the handling and transport conditions and to choose the related optimum parameters. The results of finite element modal calculations as well as experimental modal analyses are presented and compared. The maximum accelerations admissible during transport with several types of vehicle were computed. The accelerations experienced by both types of cryo-magnets were measured during real transport with different vehicles. The dynamic deformation of the support posts in the cryo-dipole was also measured. The methodologies of these analyses and their results are reported as well as the resulting specification for the transport during the LHC installation.