Development of Novel Experimental Method by Polarized Neutrons

在启动这个项目时，我们的目标是建立两个主要的学科：一个是所谓的新版本的中子自旋回波，另一个是中子极化测量。这两种技术都是在劳厄朗之万研究所（ILL）开发的，但ILL的高通量反应堆由于更换反应堆容器而长期关闭。由于日本中子散射科学家渴望开发利用极化中子的实验技术，因此邀请ILL的科学家参与极化中子技术开发项目是一个很好的合作机会。我们一直在努力推动两个主题，我们可以使至少一个非常成功。简要介绍了我们两年来所取得的成果。中子自旋回波（NSE）方法的原理是，除了中子通量的“速度”之外，中子自旋绕稳恒磁场的拉莫尔旋进还可以作为标准“时钟”。当极化时， ...更多信息 中子通过两个磁通道，其中通过两个通道的磁场非常相同。然后在两个通道的中心，中子自旋旋转被迫完全逆转。最终，仅在第二磁通道的出口处的中子极化回到与第一通道的入口处的极化相同的状态，这被称为回波。将这一原理应用于真实的NSE装置中，研究了冷中子源与高分辨中子能谱的结合。在这里，我们通过使用热中子以及三轴光谱仪来挑战新版本的NSE光谱。由于中子速度较大，且样品位置前后的中子路径几何不对称，回波条件难以实现。然而，ILL的科学家们开发了一些新的想法，但他们没有机会通过实验证明。在这个项目中，我们都构建了一个原型NSE机器，它设置在PONTA的三轴光谱仪上（JRR 3的5G端口）。寻找了许多有待解决的问题。最后，我们对中子极化法的性能进行了测试，得出了中子极化法在能量分辨率上具有良好的灵敏度以及中子极化法本身的可行性。因此，我们主要研究了如何提高中子的极化度，并得出结论，极化度是可以得到提高的。少

When we initiated this project, we aimed construction of two main subjects : One is the so called a new version of neutron spin echo, and the other is the neutron polaritometry. Both were already developed at Institute Laue Langevin (ILL), but the High Flux Reactor of ILL have been shut down for long due to the replacement of the reactor vessel.Since Japanese neutron scattering scientists were eager to develop the experimental techniques utilizing polarized neutrons, it is a good opportunity to collaborate with the ILL scientists by inviting to this project of the technical development of polarized neutrons. We have been pushing hard two subjects and we could make at least one very successfully. We explain briefly the results what we have developed in the two years' period.The principle of the Neutron Spin Echo (NSE) method is that the Larmor precession of neutron spin around the steady magnetic field can be used as standard 'clock' besides 'velocity' of neutron flux. When polarized ne … More utrons pass through two magnetic channels in which the magnetic field is very identical through two channels. Then at the center of two channels, neutron spin rotation is forced to completely reverse. Eventually neutron polarization at just the outlet of the second magnetic channel is back to the same state of the polarization at the inlet of the first channel, which is called Echo. This principle was applied to the real NSE machine, with which we investigate the high resolution neutron spectroscopy combined with cold neutron source. Here we challenge a new version of NSE spectroscopy by using thermal neutrons as well as triple axis spectrometer. Since neutron velocity is larger and neutron path is not symmetric geometrically before and after the sample position, the echo condition is hard to realize. However the ILL scientists developed a number of new ideas but they had no chance to prove experimentally. In this project we both constructed a prototype NSE machine, which is set on the 3-axis spectrometer of PONTA (5G port of JRR3). and searched many points to be solved. Finally we have tested the performance of this NSE method and concluded the good sensitivity in energy resolution as well as the feasibility of the novel NSE technique itself.As for the neutron polaritometry, we have encountered unexpected difficulty of getting high quality polarizer, which have been installed at the triple axis spectrometer of TOPAN (6G port of JRR3). Therefore we have investigated how to improve neutron polarization mostly, from which we conclude now that the polarization can be improved as we aimed initially. Less