SUPERCONDUCTING SPIN PRECESSION MAGNETS FOR A NEW NEUTRON SPECTROMETER

The required field shape of optimal Larmor precession magnets to obtai n the best possible homogeneity is B(0)cos(2)(pi z/L). In practice thi s field shape is approximated by 30 superimposed concentric solenoids. The coils are made with an extreme dimensional precision with a typic al error of 10 mu m. A special winding technique in combination with a relatively thin superconducting wire of 230 mu m diameter provided a significant overall accuracy. In this paper the design and constructio n aspects of the superconducting Larmor precession magnets will be dis cussed. Results of the magnetic field optimisation as well as prelimin ary test results of the magnets are presented. However, the ultimate p erformance will be investigated when the magnets are put into operatio n in the new neutron Larmor precession spectrometer at the Institut La ue Langevin.