Design and manufacturing of the SNS accumulator ring and transport system dc magnets

Abstract

The Spallation Neutron Source accumulator ring requires large aperture dipole magnets, strong focusing quadrupole and sextupole magnets, and low field corrector dipole, quadrupole, sextupole, and octopole magnets. All of these magnets will provide a fixed magnetic field throughout the accumulator's fill/storage/extraction cycle. Similar fixed field magnets are also being built for the beam transport lines from the linac and to the target. Because of the high intensity in the accumulator, the magnets must be built with tight tolerances for optimum field quality. Because some of the magnets are powered in strings, those magnets must have tight tolerances and consistent material properties to provide the same integral field from magnet to magnet. Radiation resistance, maintainability, and cost were other major factors in determining the magnets' design. The accumulator ring and transport line lattice design required 32 different magnet types out of the 312 magnets to be installed. This resulted in small quantity procurements that affected the cost of fabrication and testing of the magnets.