Analysis of the mechanical behavior of an 11.5 T Nb3Sn LHC dipole magnet according to the ring collar concept

This paper report that, according to the CERN-LHC reference design, 10 tesla twin-aperture NbTi dipoles will be built with split collars that enclose both apertures. As part of the development program towards and experimental 11.5 tesla Nb3Sn LHC dipole magnet, the mechanical implications of an alternative collar concept have been studied with a finite element analysis. In this concept ring shaped collars are shrunk on each finished single aperture coil, thus providing the necessary room-temperature prestress. This system results in a major improvement of the stress distribution in the collars. Introduction of friction at the sliding planes can cause reopening of the gap between the yoke halves during excitation. This depends strongly on the value of the friction coefficients