Neutron polarisation and polarisation analysis with 10-4 accuracy and design of the beam line for PERC

PERC和其他研究中子衰变相关性的项目目前由于对平均中子束极化的了解，精度限制在10-3水平。在这个项目中，大致单色（∆λ/λ约10%）冷中子束的偏振技术将被推向10-4的水平。这包括开发和测试优化的超级镜面偏振器和能够在高磁场下工作的中子自旋鳍，以及使用3He中子自旋滤波器挑战极化分析的限制。可以预期的是，只有在整个光束线的优化设计中，包括偏振分析，才能获得偏振精度的尝试水平。这是该项目的最终目标，对于新的PERC仪器，还包括中子速度选择器和斩波系统以及中子自旋输运等光束整形组件的优化。

PERC and other projects investigating correlations in neutron beta decay are presently limited in accuracy at the 10-3 level by the knowledge of the average neutron beam polarisation. In this project, techniques for the polarisation of a roughly monochromatic (∆λ/λ about 10%) cold neutron beam will be pushed towards the 10-4 level. This includes developing and testing optimised super mirror polarisers and neutron spin flippers capable of working in high magnetic fields as well as challenging the limits of polarisation analysis using 3He neutron spin filters. It is expected that the attempted level of precision in polarisation can only be obtained in an optimised design of the full beam line, including polarisation analysis. This is the final goal of this project, for the new instrument PERC, and comprises also the optimisation of beam shaping components as neutron velocity selector and chopper system and of neutron spin transport.