Structural design and analysis of a compact sweeper magnet for nuclear physics

A superconducting dipole, designed for use as a sweeper magnet in nuclear physics experiments, is being constructed by the NHMFL for operation at the NSCL. The magnet operates at a peak field of 3.8 T in a 140 mm gap. A multi-particle beam enters the magnet from the upstream side. The neutrons continue straight through to a neutron detector. The charged particles are swept 40 degrees on a one-meter radius into a mass spectrometer. To allow space for the exit of the downstream neutron beam, the magnet iron and coil structure are built in a modified "C" configuration. There are two coils of "D" shape, one above and one below the beam. This configuration keeps the magnet compact and removes the need for a negative curvature side. The peak field in the winding is 6.5 T. The net force on the curved leg of a single "D" is 1.6 MN. Design of the structure to contain these forces in a superconducting magnet of such a geometry is presented along with details of stability and quench analysis, field profiles, etc.