多晶氘中的相干中子散射及其对超冷中子产生的意义
Coherent Neutron Scattering in Polycrystalline Deuterium and its Implications for Ultracold Neutron Production
摘要：
本文提出了一种计算固体材料（用于实际中子源）中的中子截面的方法，该方法具有较大的相干散射贡献。特别地，多晶ortho-D $_2$的动态结构函数S（Q，$ω$）使用Monte-Carlo计算来评估，所述Monte-Carlo计算在相对于随机取向的晶轴的散射角上执行平均。该方法使用的解析色散函数与力常数来自单晶D $_2$的中子散射数据的轴对称力张量的框架。由此产生的二维地图的S（Q，$ω$）捕获的声子分支的细节，以及分子的旋转，可以直接从多晶D $_2$上的非弹性中子散射的数据进行比较。利用这些高分辨率信息计算了超冷中子（UCN）的产生和上散射损失的绝对截面。所得的散射截面显着不同，特别是对于UCN上散射，从以前的预测使用的方法集中在非相干近似。
英文摘要：
This paper presents a calculation of the neutron cross-sections in solid materials (used in practical neutron sources) with a large coherent scattering contribution. In particular, the dynamic structure function S(Q, $ω$) of polycrystalline ortho-D$_2$ is evaluated using a Monte-Carlo calculation that performs an average over scattering angles relative to crystal axes in random orientations. This method uses an analytical dispersion function with force constants derived from neutron scattering data of single crystal D$_2$ in the framework of an axially symmetric force tensor. The resulting two dimensional map of S(Q, $ω$) captures details of the phonon branches as well as the molecular rotations, that can be compared directly to data from inelastic neutron scattering on polycrystalline D$_2$. This high resolution information is used to calculate the absolute cross-sections of production and upscattering loss of ultracold neutron (UCN). The resulting scattering cross-sections are significantly different, especially for UCN upscattering, from the previous predictions using the approach centered on the incoherent approximation.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
