A high homogeneous field superconducting magnet for Argonne polarized proton target

We have designed and built a superconducting magnet for a large polarized proton target. The magnet consists of a pair of thick Helmholtz coils. Each Helmholtz coil consists of 9 step-subcoils balancing the ampere-turns around the Helmholtz line, thus providing an optimum for field uniformity without the help of Correction coils. This magnet generates 25 kilogausses with field uniformity one part in 10,000 over more than 5 cm diameter spherical target volume. It was designed to allow a large warm bore of 34.5 cm with axial aperture of 96° and between the Helmholtz pair, a wide warm separation of 12.7 cm with transverse aperture of 23°, thus allowing large accessibility to the proton target and for the scattering detectors in high energy scattering experiments.