Abstract
| The use of superconducting composite cables based
on Nb3Sn, an intermetallic compound of Niobium and Tin, is one
of the favorite routes to reach magnetic fields higher than 10 T
in state-of-the-art accelerator magnets. The brittle and nonlinear
nature of the epoxy-impregnated Nb3Sn Rutherford cable makes
challenging to predict its mechanical limits and, consequently, the
overall performance of the magnet. In the case of collared magnet
structures, peak stresses in coils are usually reached during the
collaring procedure performed at room temperature. Hence, it is
essential to extensively study stress distribution within the superconducting coils and at their interfaces with other components during this phase. In this context, a combined experimental/numerical
methodology was developed at CERN to investigate the effects
of the assembling process and geometrical imperfections on the
mechanical response of the collared coil of the 11 T HL-LHC dipole.
The results of the experimental tests were benchmarked against 3-D
non-linear finite element models, using material constitutive laws
that mimicked the non-linear responses of the Nb3Sn cable, and
embedding geometrical imperfections as measured on the tested
components. The proposed methodology, used in the early stages
of superconducting magnets development, may help to identify
limitations in the mechanical design, and understand the impact
of geometrical imperfections and tolerances on stress distribution
in the magnet structures. |