Effect of interfacial roughness correlation on diffuse scattering intensity in a neutron supermirror

Maruyama, Ryuji   ; Yamazaki, Dai  ; Ebisawa, Toru*; Soyama, Kazuhiko  

Neutron supermirrors are one of the most useful multilayer devices in neutron experiments since a polychromatic neutron beam can be reflected. The diffuse intensity from a supermirror has to be suppressed since it causes a serious problem of low signal to background noise in focusing systems. The diffuse intensity can be decreased by more than an order of magnitude by adopting NiC/Ti multilayers instead of conventional Ni/Ti multilayers, which leads to a high performance focusing system with a diffuse intensity down to the order of 10 of the specular intensity. In this study, in order to obtain the mechanism that controls the diffuse intensity from a supermirror, we investigated the crystal structure of Ni and NiC monolayers and the interface structure of Ni/Ti and NiC/Ti multilayers and demonstrated that a multilayer with a large vertical correlation length and a small lateral correlation length effectively suppresses the diffuse intensity from a supermirror.