Development of Novel Experimental Method by Polarized Neutrons

点击翻译按钮获取中文摘要

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