Improved Performance of Multilayer Neutron Monochro- mator by Addition of Hydrogen in Titanium Layer

mator by Addition of Hydrogen in Titanium Layer The current neutron guides and super mirrors are made of alternatively repeating Ni−C and Ti Multilayer(ML) coating. The most important factors required to obtain the highperformance reflectivity from neutron guide or super mirror coating are to select proper materials with the large scattering length density contrast, to regulate the bilayer thickness, and to maintain each layer as smooth and flat as possible. One of the methods to improve the neutron reflectivity is enhancing the contrast between two deposition components. The scattering length densities of Ni, Ti, and H are 9.41 × 10−6Å, −1.95 × 10−6Å, and −2.01× 10−6Å respectively. Therefore, the improvement can be obtained by the addition of hydrogen atoms into Ti layers, to form the titanium hydride (TiH2), the scattering length density of which is ideally −5.14 × 10−6Å. Two parallel sets of multi-layer(ML) films, withand without-hydrogen, were prepared by a magnetron sputtering technique. The number of bilayers(BLs) in each series was varying from 1 to 40, with a typical bilayer spacing of 84Å. All the samples were measured at POSY II, Intense Pulsed Neutron Source, Argonne National Laboratory. The neutron reflectivity comparison between two parallel sets demonstrates that the first order Bragg’s peak intensities of all with-hydrogen samples were significantly elevated by 64 % on average and the maximum intensity was observed up to 56.1 % at the kz = 0.0383 Å . The peak intensities of both Ni/T i and Ni/T iH2 systems were lower than the theoretical as the more layers were deposited. The roughness of the films mainly causes the drop of the reflectivity performance. The blurriness of the interfaces between Ni and Ti layers was observed by Auger Electron Spectroscopy(AES) and the existence of hydrogen in Ti layers shapened the interfaces. The formation of TiH2 in the with-hydrogen samples was confirmed consistently with the data fit analysis onto the neutron reflectivity. The purpose of this work will focus on the neutron reflectivity response, including the data-fits, the correlation between the neutron reflectivity performance and the