Pre-manufacturing Design of the Superconducting Dipole Magnet for the CBM Detector

The CBM detector will research compressed baryon matter on the FAIR facility, GSI, Darmstadt. The superconducting dipole magnet of this detector provides vertical magnetic field with field integral similar to 1 T*m along a beam length of 1 m. The warm bore distance between the dipole coils is 1.44 m. Maximal magnetic field on the superconducting winding is 3.6 T. The stored energy of the magnet is similar to 5 MJ. The superconducting coils having 1.34 m of inner diameter will be made of NbTi wire having Cu/SC ratio of 7/1. The SC wire cross-section bare size is 2.02 mm x 3.25 mm. This wire of 30 km of total length in 6 pieces was manufactured by extrusion monolith technique. The iron yoke having 139 t weight is a part of the CBM magnet. It was manufactured and assembled. The SC coils were designed according the indirect cooling principle. The superconducting winding is embedded in copper case and will be cooled by 4.5 K helium going through the copper tube attached to the copper case. Two dummy coils were manufactured and tested to choose the epoxy impregnation procedure. The cooling helium will circulate between the cryostat containing 150 l of LHe and two coils in thermosyphone regime in single loop. The vapor quality at the outlet of the thermosyphone loop is similar to 10%. The each coil is affected by 3 MN axial force towards the nearest iron yoke. The single cylinder GFRP support strut was designed to withstand this force to have the safety factor > 4 with respect to the ultimate strength and buckling. The GFRP material was chosen and tested.