Neutron spin echo optics

Recently proposed experiments for neutron spin optics were extensively carried out using a transverse neutron spin echo (NSE) instrument for the neutron optics, which was installed at CN3 guide tube of the cold neutron source at Kyoto University Reactor (KUR). By setting a crystal or a magnetic film in one of the Larmor precession fields, a phase shift and a change of the NSE signals through the sample were observed. The shift of NSE signal through the sample was interpreted as the phase change between ↑ and ↓ spin wave functions of neutron as in the following cases: (1) measurement of refractive index of Si crystal by forward scattering NSE method, (2) measurement of traversal times through a magnetic thin film (Fe, or permalloy) above the critical angle of total reflection by the Larmor clock, (3) neutron spin interference of tunneling neutrons through the magnetic thin films and (4) phase interference of neutron spin wave functions in the forward scattering through a magnetic multilayer in case of the Bragg reflection observed by NSE signals. (author)