2D Magnetic Design and Optimization of a 88-mm Aperture 15 T Dipole for NED

The Next European Dipole (NED) activity supported by the European Union aims at the development of a high-performance Nb$_{3}$Sn conductor ( c = 1500A mm 2 @15 T, 4.2 K) in collaboration with European industry and at the design of a highfield dipole magnet making use of this conductor. In the framework of the NED collaboration which coordinates the activity of several institutes,CERNhas contributed to the electromagnetic design study of a cos , layer-type superconducting dipole with an 88 mm aperture that is able to reach 15 T at 4.2 K. Part of the optimization process was dedicated to the reduction of the multipole coefficients so as to improve field quality while keeping an efficient peak-field to main-field ratio. In this paper, we present the optimization of the coil cross-section and of the shape of the iron yoke to reduce saturation-induced field errors during ramp. The effects of persistent magnetization currents are also estimated and different methods to compensate persistent-current-induced field distortions are presented.