<title>Characterization of neutron mirrors and supermirrors using x-ray and neutron measurements</title>

Abstract

Neutron mirrors and super-mirrors (Ni/Ti, NiC/Ti, Ni/TiH and NiC/TiH) are prepared on borkron (float) glasses or silicon wafers. The period d of the multilayers can be obtained by using small angle x-ray diffraction like those obtained with the white neutron beam measurements made at SACLAY. Large-angle x-ray diffractions can give the structures of the materials, namely, amorphous or crystalline states, and the textures. X-ray rocking curves can further determine the degree of texture perfection. By mixing carbon into nickel layers, the crystalline size of Ni was reduced. As a consequence, smoother interfaces are expected and indeed have been confirmed by x-ray reflectivity in NiC/Ti multilayers. This effect is observed directly by cross-sectional sampled transmission electron microscopy. Nickel still had a cubic structure after mixing the carbon. The addition of a small amount of carbon into the nickel layers can increase in neutron scattering length density by several percentages, but hexagonal Ni3C can only yield a 0.5% improvement as compared with pure nickel. Putting hydrogen into the titanium layers not only made the neutron scattering length density more negative but it also prevented interdiffusion between the nickel and titanium layers. In order to compare their thermal stability, three multilayers, Ni/Ti (100 layers), NiC/Ti(100 layers) and NiC/TiH (20 layers), were chosen to be annealed at different temperatures. Then x-ray diffractions were used to study the structures of their layers. All these characterization are essential at the beginning of the fabrication of neutron mirrors and supermirrors.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.