Neutron β decay with Ultracold neutrons

本研究工作的目的是用超冷中子（UCN）进行β衰变实验。高密度UCN在UCN实验中是非常理想的。我们研究了散裂中子在超流氦（He-II）中产生UCN。在此基础上，我们建立了一个散裂中子源、重水热中子和冷中子减速器以及用于生产UCN的He-II低温恒温器。我们在新一代UCN源上成功地进行了UCN的制作和观测。我们通过在UCN探测器前放置一个完整的UCN反射器并改变He-II的温度来证实UCN观测。自然保护联盟的统计与预期的一样有所不同。我们研究了UCN检测器的效率，然后在实验瓶中得到了UCN密度。当质子束功率为156 W时，质子束能量小于100 neV时，该值为1.4 UCN/cm^3。UCN密度与格勒诺布尔的UCN密度相比具有竞争力，格勒诺布尔是世界上最大的UCN密度。我们期望通过改进质子束功率、He-II稳压器和中子慢化反射器的配置，UCN密度将大于10000 UCN/cm^3。我们把结果发表在了《物理学》杂志上。启。超冷NeutronSymmetry

The aim of this research work was to carry out a β decay experiment with ultracold neutrons (UCN). High density UCN are highly desirable for the UCN experiment. We have studied UCN production in superfluid helium (He-II) with spallation neutrons. Based on this study, we built a spallation neutron source, thermal and cold neutron moderators with heavy water and a He-II cryostat for the UCN production. We succeeded in the UCN production and observation in the new generation UCN source. We confirmed the UCN observation by placing a complete reflector for UCN in front of a UCN detector and changing the temperature of He-II. UCN counts varied as it was expected. We studied a UCN detector efficiency and then obtained a UCN density in a experimental bottle. The value was 1.4 UCN/cm^3 for UCN energies less than 100 neV at a proton beam power of 156 W. The UCN density is competitive to UCN density at Grenoble which is largest in the world. We expect the UCN density will be larger than 10000 UCN/cm^3 by improvement of the proton beam power, the He-II ctyostat and aneutron moderator reflector configuration. We published the result in Phys. Rev. Lett.Ultracold NeutronSymmetry