Development ofanewneutron spin echo spectrometer using multilayer spin splitters

多层自旋分离器(MSS)是由磁镜、间隙层和非磁镜组成的多层膜。当处于磁平行和反平行分量叠加态的中子入射到MSS时，由于平行和反平行分量被不同的层反射，所以在两个自旋分量之间引入了相位差。从量子力学的观点来看，这一位相差相当于磁场中中子的拉莫尔进动角。本研究的目的是将中子自旋回波(NSE)仪器中的巨型磁铁替换为MSS，并研制出各种类型的新型自旋回波仪器。研究结果如下：a.为了取代NSE光谱仪中的进动磁场，应将一对MSS组合成(++)型，以避免由于束流发散而导致的极化降低。通过磁控溅射技术，MSS中的GaP层的均匀性约为7 nm，这为NSE光谱仪提供了低偏振度。相反，真空蒸发技术给了我们足够的层均匀度。我们利用MSS的S.D.成功地进行了NSE的初步实验。我们研制了小型共振中子自旋翻转装置，并成功地获得了频率高达300 kHz的NSE信号。这些小型共振自旋翻转装置，加上低磁场驱动的偏振镜，使我们能够与其他光谱仪，如反射仪或小角衍射仪相结合。为了将这些NSE仪器应用于散裂中子源，我们构建了根据中子飞行时间改变共振自旋自旋翻转装置中共振电流的幅度的系统。

The multilayer spin splitter (MSS) is a multilayer consisting of a magnetic mirror, gap layer, and a non-magnetic mirror. When a neutron in a superposing state of magnetic parallel and anti-parallel component is incident to the MSS, a phase difference is introduced between the two spin components since the parallel andanti-parallel component is reflected by the different layer. This phase difference is equivalent to the Larmor precession angles of neutron in a magnetic field, in the quantum mechanical point of view. The aim of this study is to replace the huge magnet in neutron spin echo (NSE) instrument by MSS, and develop various types of new spin echo instruments.The results obtained in the present study are as follows :a. To replace precession magnetic field in NSE spectrometer, a pair of two MSS's should combine in (++) configuration so as to avoid the reduction of polarization due to beam divergence.b. Via magnetron sputtering technique, the homogeneity of the gap layer in MSS is about 7nm, which gives low polarisability for NSE spectrometer.c. On the contrary, vacuum evaporation technique gives us enough layer homogeneity. We have succeeded toperform preliminary NSE experiment using MSS 's.d. We have developed small resonance neutron spin flippers and succeeded to get NSE signal with the frequency up to 300kHz. These small resonance spin flippers, with low-magnetic field driven polarizing mirror, enables us to combine NSE instruments with other spectrometers, such as, reflectometers or small angle diffractometers.In order to apply these NSE instruments to spallation neutron source, we constructed the system to change the amplitude of the ocsillating current in resonance spin flipper according to the flight time of neutrons.