Development of higher m supermirrors

Supermirrors are important components of neutron guides used for performing neutron scattering experiments for from the reactor core to the instruments, where the background is low enough to permit measurements of even week signals. We will present the methods used at our facility to produce supermirrors, the trials that we have made to increase the performances of supermirrors and the results obtained from the neutron reflectivity measurements. Using the Hayter and Mook algorithm we have simulated sequences with increasing number of Ni and Ti layers and we have achieved a neutron reflectivity of around 84% for m equal to 3. The next step in improving our facility was to try the reactive sputtering process (by using N and air as sputter gas together with Ar) in order to achieve the deposition of more layers and therefore of higher m-values. X-ray and neutron reflectivity measurements as well as X-ray diffraction and profilometry for the stress analysis were performed in order to determine the proper parameters for the sputtering of Ni. As a consequence we have produced supermirrors with higher m values that were not able to achieve without the reactive sputtering of Ni. Neutron reflectivity measurements for the produced supermirrors show promising results.