Multiple-channel collimation for improved performance of SANS instruments

Complete text of publication follows. Small Angle Neutron Scattering (SANS) is a powerful technique for the investigation of the submicrometer structure of condensed matter, and has found important applications in materials science and engineering, solid state physics, polymer research and biological sciences. SANS facilities are currently heavily demanded and several new such instruments are planned for installation. However, the existing facilities, due to the design adopted for the layout as well as the mode in which they operate can, in general, be upgraded. An analytical study is presented on the performance of a SANS instrument equipped with a multi-aperture pinhole collimator. This collimation can provide large count rate gains, which might attain one order of magnitude, for the usual resolution required in SANS measurements. Both pulsed and steady-state neutron sources are considered in the study. For pulsed source installation such collimation was found to be ideal because is not only provides the optimisation of count rate and resolution but it also avoids the problem of frame overlap, as relatively small collimation lengths are required. For steady-state neutron source installation the referred optimisation is achieved but the versatility in reciprocal space range becomes reduced. Finally, a new type of honeycomb collimator based on the results presented is proposed. (author)