Effectiveness of a modest sorting of LHC dipoles

It is shown that by sorting a modest number of dipoles, twelve to twenty-four, before installing them in consecutive locations within an arc octant, one can avoid unlucky situations in which the amplitude of various low-order resonance driving terms may exceed the statistically expected value by a factor of two or more. This is possible even for two-in-one dipoles in which there is no correlation between inner and outer field multipoles. Sorting procedures and the èfigure-of-meritè(or èquality factorè) used in the sorting are explained and results for sorting 1) 24 magnets, 2) 18 magnets, and 3) 12 magnets as a sorting group are presented. As a special case, all possible combinations (6!x6! = 518400) for two groups of six magnets each are examined to see its effectiveness.