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Description
The Spectrometer Section (SPS) is a critical part of the ongoing High Rigidity Spectrometer (HRS) project at FRIB, Michigan State University. The HRS can accept high rigidity beam up to 8 Tm from FRIB and will significantly enhance the scientific output. One of the key components in the SPS is a large-scale, rectangular-shaped iron-dominated superconducting dipole magnet DS1. The overall dimensions of this large magnet with warm iron yoke are 6.6 meters wide, 4.6 meters tall and 2.835 meters long, with a large primary steel pole gap of 0.6 m. The magnet is to be designed with the ability of steering beams of 8Tm rigidity with a central mid-plane field of ~ 2.26 T and a field inhomogeneity of less than 0.1% within ±0.47 m around geometrical center at bisecting plane. The warm iron primarily shapes the dipole field, field clamps made of ferromagnetic steel were added onto the upstream and downstream sides of the steel to minimize the stray field effect on nearby electronic devices. Superconducting coils made of NbTi conductors were used to excite the magnet, which are located around chamfered primary poles. Large rectangular Wire-In-Channel (WIC) NbTi wire with a bare dimension of 3.25 by 2.02 mm was chosen with several considerations: 1) winding feasibility, 2) power supply requirements of the large cross section of the coil designed and 3) iterative conductor ramp loss studies. The ratio of copper to superconductor in the conductor on average is around 7. To overcome large internal voltage generation during quench at a current near 500 A as well as the limited wire conductor length issue, each of the dipole coils is sub-divided into 3 sub-coil segments. The overall 6 sub-coils for this dipole magnet will be wet wound with Stycast 2850FT and cooled by liquid helium. A circuit with cold diodes for preventing the unbalanced forces on supporting links during certain quench conditions is designed and evaluated. The radial force and stress on epoxy during quench between each of the sub-coils were calculated and analyzed.
