Selection of the cross-section design for the LHC main dipole

With the aim of selecting the most suitable design for the series productio n of the LHC main dipoles, several possible configurations were analysed wi th respect to admissible component tolerances and structural stability, fie ld level, field quality, number and weight of parts. Two alternatives desig ns, featuring common collars made out of aluminium alloy and austenitic ste el, respectively, were finally compared in detail. Although both designs ar e almost equivalent at nominal conditions, the austenitic steel collar stru cture turned out to lie far less sensitive to components dimensional variat ions. This paper reports the main results of the above evaluations, which l ead to the choice of austenitic steel collars for the LHC main dipoles.