Field quality in the LHC main quadrupole prototzpe before the cold tests

The field shape harmonics of the first superconducting main quadrupole prototype with the nominal design for LHC have been measured by CEA in Saclay at room temperature with rotating coils. The measurements were made during the quadrupole assembly. They provide information on field-shape quality before the execution of the cold tests. The measured values of the allowed components b6 and b10 differ from those computed for the nominal coil geometry. We show that a displacement of the inner coil blocks may induce this effect. The random components are also considered. We show that their measured values are compatible with a random displacement of the blocks characterised by a standard deviation of about 25mm. Scaling laws for multipoles induced by random displacements are worked out.