Construction of optimized superconducting spin precession magnets for neutron spectroscopy

The design and construction of a superconducting magnet system for a high-resolution neutron spin echo spectrometer. The principal solution for the field shape of optimal precession magnets is B0 cos2(¿z/L). In practical precession magnets, this field shape is approximated by 30 superimposed concentric solenoids with a bore of 80 mm. The required field integral of 1 Tm, providing 104 precession turns, is achieved in a magnet with a length of about 1.5 m. The field in the center is 1.5 T maximum. The relative line integral inhomogeneity of about 10-3 obtained with such a coil is improved to less than 10-6 by two in-beam correction coils. The advanced homogeneity level means that after 10000 precession turns the precession angle remains still well defined without using tedious correction procedures