Design, Fabrication and Measurement of Ni/Ti Multilayer Used for Neutron Monochromator

Abstract

Ni/Ti multilayers, which can be used for neutron monochromators, are designed, fabricated and measured. Firstly, their reflectivities are simulated based on the Nevot–Croce model. Reflectivities of two Ni/Ti multilayer mirrors with periods d = 10.3 nm (M1) and d = 7.8 nm (M2) are calculated. In the calculation, the reflectivity of the Ni/Ti multilayer is taken as a function of the grazing angle with different roughness factors δ = 1.0 nm and δ = 1.5 nm. Secondly, these two multilayers are fabricated by the direct current magnetron sputtering technology. Thirdly their structures are characterized by small-angle x-ray diffraction. The roughness factors are fitted to be 0.68 nm and 1.16 nm for M1 and M2, respectively. Finally their reflective performances are measured on the V14 neutron beam line at the Berlin Neutron Scattering Centre (BENSC), Germany. The experimental data show that the grazing angle of the reflected neutron intensity peak increases, but the reflected neutron intensity decreases, with the decreasing periods of the multilayers.