Development ofanewneutron spin echo spectrometer using multilayer spin splitters

多层膜自旋分裂器（MSS）是由磁镜、带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状态的中子入射到MSS时，由于平行和反平行分量被不同的层反射，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，这个相位差相当于中子在磁场中的拉莫尔旋进角。本研究的目的是用MSS代替中子自旋回波（NSE）仪中的大磁铁，研制各种新型的NSE仪。在NSE谱仪中，为了取代旋进磁场，一对两个MSS应联合收割机成（++）配置，以避免由于光束发散而导致的偏振度降低。通过磁控溅射技术，获得了均匀性约为7nm的差距层，为NSE光谱仪提供了较低的极化率。相反，真空蒸发技术给我们足够的层均匀性。我们已成功地用MSS’s. d进行了初步的NSE实验。我们研制了小型共振中子自旋翻转器，并成功地获得了频率高达300kHz的NSE信号。这些小型共振自旋翻转器具有低磁场驱动的偏振镜，使我们能够将NSE仪器与其它谱仪（如反射仪或小角衍射仪）结合起来，为了将这些仪器应用于中子源，我们构建了一个系统，根据中子的飞行时间来改变共振自旋翻转器中振荡电流的幅度。

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.