Development of new, non-depolarizating and high reflective coatings based on B-C-N compounds for application in fundamental neutron physics

自由中子的基础物理研究是检验低能标准模型的重要手段之一。这一领域最突出的候选者是寻找电偶极矩和测量中子寿命。利用超冷中子（UCN）进行实验测定的显著改进需要减少系统误差和统计误差。新的超冷中子超热源将使目前的UCN密度（ILL为40/cm 3）提高约10至100倍。与此同时，迫切需要在新的中子导向器和中子存储材料方面取得进展，以便从更高的UCN密度中受益。这里需要优化（最小化）的关键参数是中子的临界速度，这与寻找具有高中子光学势（费米势）和中子损失率的材料直接相关。该项目的主要目标将是开发基于B-C-N化合物的新型涂层材料，使用高浓缩硼11，与10 B相比，它显示出低中子吸收截面。这种类型的化合物可能是UCN运输和储存的突破。它们在基础中子物理学中的使用将显著提高即将到来的实验的性能，如中子电偶极矩（EDM）实验，例如，目前正在保罗谢勒研究所（PSI）进行的n2 EDM实验。

Research in fundamental physics of the free neutron is one of the key tools for testing the standard model at low energies. Most prominent candidates in this field are the search for an electric dipole moment and the measurement of the neutron lifetime. Significant improvements of the experimental determination using ultracold neutrons (UCN) require reduction of both systematic and statistical errors. New, superthermal sources for ultracold neutrons will enhance the present UCN densities (≈ 40/cm3 at ILL) by about a factor of 10 to 100. At the same time, progress in new neutron guides and neutron storage materials is urgently needed in order to benefit from the higher UCN densities. The crucial parameters to optimize (minimize) here are the neutrons’ critical velocity directly connected to a search for materials with high neutron optical potential (Fermi-potential) and the neutron loss rate. The main goal of this project will be the development of new coating materials, based on B-C-N compounds using highly enriched boron 11, which in contrast to 10B shows a low neutron absorption cross section. Compounds of this type may be a breakthrough in UCN transport and storage. Their use in fundamental neutron physics will increase significantly the performances of upcoming experiments like the neutron electric dipole moment (EDM) experiments, e.g., the n2EDM experiment currently under construction at the Paul Scherrer Institute (PSI).