$rm Nb_3rm Sn$Sextupole Magnet for Neutron Beam Focusing

In order to obtain a high-intensity neutron beam for neutron scattering experiments, strong sextupole magnets with large apertures are useful as a focusing element. We have started the development of a Nb₃Sn sextupole magnet for this purpose. The design field strength of the sextupole is 12780 T/m² and the aperture of the coil is 46 mm in diameter. As a first step of the development, three model coils have been made in order to learn about Nb₃Sn technology and to evaluate the fabrication techniques. Single-pole tests of these coils have been performed to assess the conductor stability and training behavior of the Nb₃Sn coils. This paper describes the design of the magnet, the fabrication of the model coils and the results of single-pole tests