12  The Union framework: sample environments and multiple scattering

The Union framework, contributed by Mads Bertelsen (University of Copenhagen) [Ber17; BJL17], is a set of components that together allow the description of complex, possibly nested or overlapping, sample environments with multiple scattering, by separating the description of geometry (where matter is) from physical process (what happens to a neutron there). For a conceptual introduction to the framework – volumes, priority, masks, exit volumes, loggers, conditionals, tagging, and the underlying propagation algorithm – see chapter A.5.4. This chapter documents the input parameters of every individual Union component.