Field quality analysis of the next generation IR quadrupole for the LHC

Lawrence Berkeley National Laboratory (LBNL) is carrying out a conceptual design study of a Nb₃Sn quadrupole for the next generation LHC Interaction Region (IR). The choice of a gradient of 205 T/m and an increased bore size of 90 mm represents a promising strategy towards increasing the luminosity up to an ultimate goal of 2.3 × 10³⁴ cm^-2s^-1. At the present time Nb₃Sn is the only conductor with sufficient current density for this application. Coil designs with either two or four layers are being considered. Previous studies have examined cable and coil parameters, systematic harmonics, support structure and quench protection system. In this paper the issue of field quality is further discussed.