Field-shape variation induced by thermal cycling and excitation in the LHC dipole

The field-shape imperfections measured at room temperature before and after thermal cycling and excitation up to maximum field in three 10 m-long models of the LHC dipole are presented. A systematic variation is observed in the normal sextupole and decapole components. The variation of the other components turns out to be negligible or to randomly vary (as for normal and skew quadrupoles). We show how the systematic variation can be justified by assuming outward radial shift in four blocks of the inner coil. Qualitative tests using Fuji paper confirm this conjecture