Ultracold neutron production in polycrystalline deuterium through coherent neutron scattering

C.-Y. Liu, W. Fox, A. Couture, C. M. Lavelle, J. C. Long, P. M. McChesney, M. Makela, G. Manus, C. L. Morris, D. Salvat, A. Saunders, Y. Shin, and A. R. Young

Accepted Tuesday Sep 20, 2011

We present the experimental data of ultracold neutron (UCN) production, and the theoretical model required to understand the temperature dependence of UCN yield in solid D2. To mitigate the shortcomings of the incoherent approximation (IA), we construct the dynamic structure function of polycrystalline ortho-D2 using a Monte-Carlo calculation that performs an average over scattering angles relative to crystal axes in random orientations. The experimental data on the upscattering cross-sections support the new model, and disfavor the old model using IA at the 2s level.