The Study Of Algorithms About Neutron Supermirrors Design

With the development and wide application of neutron scattering and diffracting technology, higher neutron intensity, which arriving at measured samples, is required. Neutron multilayer elements are important tools for improving the utilization range of neutron source. Neutron guide based on aperiodic multilayer instead of Ni single layer can transfer several more times neutrons from the source to the spectrograph without changing the structure of neutron source. In order to achieve the large critical angle of total reflection and high reflectivity, studying the algorithm of neutron supermirrors is necessary and significant.Based on the interactions of neutron and matters, we calculate the neutron index either from the standpoint of wave or classical particle mechanics as the scattering amplitude can be easily related to the actual potential well producing the scattering. The calculation method for the reflectivity of neutron multilayer was explained. According to the method for the reflectivity of imperfect X-Ray multilayer, we discussed the working principle of imperfect neutron multilayer.We presented the method of selecting the multilayer materials for the neutron supermirrors in this paper. With this method we choose Ni/Ti that composes the neutron supermirrors.We introduced three classical design methods of neutron supermirrors. Optimize the key parameters in these methods, and compare the quality of the supermirrors designed by different algorithms. In the situation of considering the effects of interface roughness, we compare the sensitive to the roughness of three algorithms. through comparison ,we acknowledged the RSD'algorithm is the best algorithm for design neutron supermirrors.At last, the influence of film thickness control errors including a stochastic error and a systemic error on the performance of neutron supermirrors is discussed in detail. The results show that a stochastic error should be control within 5%.