Conceptual Design of a Large-aperture Dipole Magnet for HL-LHC Upgrade

The development of a large-aperture (120-180 mm) dipole magnet is proposed in the framework of the CERN-KEK cooperation program. The application target is the D1 magnet (separation dipoles) replacement for the HL-LHC (High Luminosity - Large Hadron Collider) upgrade. The Cos-theta type coil cross section and the shell-based structure are adopted in the conceptual design of this magnet. The nominal field is estimated to be 6-10 T at 1.9 K with a 30-mm-width coil arranged in two layers. The candidates of superconductor are Nb3Al, Nb$_{3}$Sn and Nb-Ti. We present the analytical estimation of the key parameters of this magnet, and the magnetic & mechanical simulation results of the actual design, including the field quality in the aperture, the stray field of the magnet, and the stress distribution in the coil.