A method to determine the flexural rigidity of the main dipole for the Large Hadron Collider

The Large Hadron Collider (LHC) superconducting dipole cold mass is a cylindrical structure 15 m long, made of a shrinking cylinder which contains iron laminations and collared coils. This structure, weighing about 28 tons, is horizontally bent by 5 mrad. Its shape should be preserved from the assembly phase to the operational condition at cryogenic temperature. Hence, an accurate comprehension of the mechanical behavior of the cold mass is required. In particular, the flexural rigidity in both horizontal and vertical directions represents one of the foremost properties. To determine the flexural rigidity, deformations of the cold mass induced by the self weight have been measured and compared with the predictions of an analytical structural model. Particular care has been taken in reducing the experimental error by an appropriate fitting procedure.