A STRATEGY FOR SAMPLING THE FIELD QUALITY OF THE LHC DIPOLES

We have measured the magnetic field of a large fraction of the LHC main dipoles, to date more than 400 in warm conditions and over 100 in cold conditions. Using the available data we analysed the distributions of the main field and higher order field errors in warm and cold conditions, as well as the distribution of the warm-to-cold correlation. Based on this analysis we predict the minimum number of magnets that should be measured in cold conditions to insure that the LHC will meet its goals. The main outcome of this analysis is that cold measurements on a fraction of the order of one third of the total production, i.e. approximately 400 dipoles, will be sufficient to achieve the above objectives.