A new method to find out the optimal neutron moderator size based on neutron scattering instrument parameters

Simple and fast analytic method to find out optimal combinations of sizes of neutron moderator and optical system entrance, allowing for the full sample illumination with minimum to none background, is developed. In the case of employing low-dimensional para-hydrogen moderators with enhanced neutron beam brilliance, the method allows to determine the minimum size of moderator, which provides the highest sample flux while keeping the sample fully illuminated. This method can be used during the design of new neutron sources, upgrades of neutron optical systems and moderator replacements.