Study of the Protection System for Cos-Theta NED Dipole

The Next European Dipole (NED) Collaboration has the scope to promote the study and development of a high magnetic field (15 T conductor peak field) and large aperture (88 mm) dipole magnet aimed at LHC upgrade and at the next generation colliders. Among different configurations, a classical cosine-theta solution is considered. This magnet will be based on a high current density (J_c around 1500 A/mm² @ 15 T, 4.2 K in the noncopper section) Nb₃ Sn superconductor, and will have a high stored magnetic energy (1.8 MJ/m, i.e. 8 times higher than for one LHC dipole), that makes the magnet protection extremely critical. In this paper we have investigated the quench propagation assuming different dump resistance values and operating conditions (quench heaters efficiency, delay time for the Quench Detector System), in order to optimize the protection system in terms of peak temperatures in the coils and maximum voltage drops. The study is performed by using two quench propagation codes, which exploit different approaches, in order to further validate our conclusions