Selection of the Cross-Section Design for the LHC Main Dipole

With the aim of selecting the most suitable design for the series production of the LHC main dipoles, several possible configurations were analysed with respect to admissible component tolerances and structural stability, field level, field quality, number and weight of parts. Two alternatives designs, featuring common collars made out of aluminium alloy and austenitic steel, respectively, were finally compared in detail. Although both designs are almost equivalent at nominal conditions, the austenitic steel collar structure turned out to be far less sensitive to components dimensional variations. This paper reports the main results of the above evaluations, which lead to the choice of austenitic steel collars for the LHC main dipoles.