Scattering Laws and Cross Sections for Moderators and Structure Materials for Calculation of Production and Transport of Cold and Ultracold Neutrons

摘要

For calculation of generation and transport of cold and ultracold neutrons scattering law data for gaseous, liquid and solid H_2 and D_2 as well as for liquid He and some structure materials were derived and applied for transport calculations. The data format of generated scattering laws is ENDF-6. The transport calculations can be performed by both multigroup programs (S_N or Monte Carlo) and with the continuous energy Monte Carlo program MCNP. In case of MCNP the production term of ultra cold neutrons is calculated externally to get sufficient statistical accuracy for UCN transport. Reflection in storage of UCN or in neutron guides is treated by a modified reflection routine. Validation is in progress by comparison of evaluated and measured cross sections and -so far available-calculated and measured neutron spectra and gain factors.