Mechanical Design and Stress Analysis of LPF2: A 12-T Hybrid Common-Coil Dipole Magnet

The Institute of High Energy Physics (IHEP, China) has been engaged in the development of shell-based dipole magnets with a common-coil configuration for the pre-study of the Super proton-proton Collider (SPPC) project. The first subscale magnet LPF1, with two Nb3Sn coils and four NbTi coils, reached a bore field of 10.2 T at 4.2 K. Subsequently a higher safety margin model has been proposed as LPF2, which has six Nb3Sn coils and two NbTi coils to reach a 12-T main field in both apertures with an operating current of 5300 A. The shell and yoke are reused from LPF1, as well as the two Nb3Sn coils and two inner NbTi coils of LPF1. The pre-loaded method of LPF2 is much alike that in LPF1: using the Bladder & Key technology to overcome the Lorentz forces in horizontal and vertical directions and pre-tightening six aluminum rods to pre-load the coil packs in the axial direction. In addition, the strain gauges are positioned at the surface of the aluminum shell to monitor the pre-loading effect. The main design parameters and stress analyses results will be presented.