Comparison of periodic and aperiodic supermirrors

The recipe used nowadays in the neutron supermirror production gives aperiodic multilayers, i.e. the layer thickness is changing from bilayer to bilayer. An algorithm recently proposed by V. Ignatovich and Carron gives supermirrors composed of periodic stacks of bilayers. Samples were prepared according to both methods and their measured reflectivity is compared. The effect of different possible faults in manufacturing is investigated by numerical calculations and a quantitative comparison is given for the different supermirror recipes. The results confirm the applicability of both design methods for practical SM production.