Measurement of Young´s modulus and shim calculation for LHC prototype dipole magnets

The superconducting coils of LHC prototype dipole magnets wound from a Nb-Ti cable of the Rutherford type are assembled in an aluminium clamping structure, the so called collars. The coils have to be prestressed in order to avoid movements of the superconductor during operation, which may cause quenches. The exact value of the prestress and the uniformity of the prestress over the length are adjusted by the thickness of inserted shims. The basis for prestressing the dipole coils is the precise measurement of the size and the Young´s modulus of the winding. Based on the measurements shims are calculated ensuring the specified prestress of the coil. During shim calculation several corrections of the shim thickness have to be taken into account e.g. corrections due to the deformation of collars. The measurement of Young´s modulus and the shim calculation are presented