Final design of a compact sweeper magnet for nuclear physics

A superconducting dipole, designed for use as a sweeper magnet for nuclear physics experiments, is being constructed by the NHMFL for operation at the NSCL. The magnet operates At a peak mid-plane field of 3.8 T in a 140 mm gap. A multi-particle beam enters the magnet froth the upstream side. The neutrons continue straight through to a neutron detector. The charged particles are swept 43 degrees on a one meter radius into a mass spectrometer. Extensive model-based computer analysis (MBA) have been applied for optimizing the coils and the stainless steel bobbin with regard to its shape while keeping the strain and the fraction of actual to critical current within reasonable limits. The structural FEM analysis had to address-a variety of complex physical phenomena (composites' with orthotropic material properties, cool down, surface-to-surface contacts, etc.) and the loads due to operation (Lorentz forces) had to be obtained from a parallel/coupled magnetic field analysis. One of the challenges magnet designers face in optimizing magnet systems. is that the detail required to obtain reasonable accuracy is not well known. This paper presents results of the structural design optimization for the sweeper project and evaluates the adequacy of alternative modeling approaches. Also the final magnetic design of the system is,summarized and progress toward fabrication is presented.