The Japanese Spallation Neutron Source Facility is based on a 3 GeV, 1 MW, 25 Hz proton accelerator. It is apart of the High Intensity Proton Accelerator Project that is a joint project between the Tokai Establishment of the Japan Atomic Energy Agency and the High Energy Accelerator Research Organization. Neutronic optimization of the target-moderator-reflector assembly has been conducted assuming that the hydrogen is almost 100% para. Target station design is also underway, and five-year contracts will be made in November this year. Various device development programs, such as neutron-optical devices and detector systems, are also actively underway.
We have been developing a neutron lens and prism based on neutron refractive optics. As a neutron has a magnetic dipole moment, it is accelerated in a magnetic field gradient. Thus, we can control a neutron beam free from beam attenuation using the magnetic field gradient. Moreover, its spin dependence of the acceleration is profitable in the case of using the polarized neutron beam. The sextupole magnetic field functions as a focusing or defocusing lens for neutrons depending on the neutron spin states. The focusing and defocusing effects of a prototype sextupole magnet was experimentally studied. By combining focusing and defocusing functions of the sextupole magnet, we can control the neutron beam shape and divergence more flexibly. Adiabatic and nonadiabatic field connections make it possible to realize the magnetic doublet system. A quadrupole magnetic field functions as a neutron prism, which were experimentally confirmed. The neutron spin and energy dependence of the refracting power is applicable to an analysis of the neutron spin and energy. In this paper, the details of the experimental results of the magnetic devices are described and their applications in the neutron scattering experiment are discussed.
We have developed compound refractive prism for cold neutrons. To prevent an increase in neutron absorption, we have developed prism array like a Fresnel lens. The prism characteristics were investigated with experimental and numerical simulation studies. We achieved transmission of 0.75 and refractive angle of 7.5 mrad for 15 neutrons with 49 layered prism array.