Cross-section models of liquid para H2 and solid CH4 for design of an advanced cold-neutron source

(a) Coherent cold-neutron scattering in liquid para-H2 and D2 is described theoretically in terms of a mean field approximation. The cross-section results, both double-differential and total, show good agreement with experimental ones at temperatures between melting and boiling points. (b) A cross-section library (group constant set) of solid and liquid CH4 is generated: 80 groups between 0.1 μeV and 10 eV at 20.4, 50, 90.7 and 111.7 K. It is shown through neutron transport analysis that cold neutron production in a solid CH4 moderator is significant especially at lower temperature as an efficient convertor of fast and thermal neutrons into cold ones