摘要
极化中子散射技术是中子散射实验技术中的一种,是当前探索物质微观结构的有力手段.在极化中子散射实验中,磁场是重要的环境因素直接影响中子极化率的传播和样品所处的环境.用于极化中子的零磁场环境是实现完全极化分析和精确极化调控的必要条件,需要通过精确的磁场屏蔽和约束实现.针对目前前沿的混合材料磁屏蔽原理,开展磁场屏蔽的有限元分析,同时通过中子极化动力学计算进行验证.研究展示经过优化的极化中子零磁场屏蔽体的屏蔽效果,以及设计参数与屏蔽效果的关系,并对屏蔽体的实际磁场约束效果进行了测量验证.
Polarized neutron scattering,as one of the experimental techniques of neutron scattering,is a powerful tool for exploring the microstructure of matter.In polarized neutron scattering experiments,magnetic field maintains and guides the neutron polarization,and determines the sample magnetic environment.For complex magnetic sample,it is often necessary to apply zero-field environment at the sample position,so that general polarization analysis becomes feasible.To achieve effective zero-field environment for polarized neutron experiment,carefully designed magnetic field is required.In this work,we demonstrate a zero-field sample chamber designed for polarized neutron experiment by utilizing both permalloy material and high-TC superconducting films.This design adopts a simple and lowmaintenance'deep-well'shape to achieve effective shielding.The study uses finite element simulation method to analyze the effect of dimensions on the magnetic field shielding performance of the device of the model,including height,arm length,opening radius,and superconductor distance.At optimal dimensions,the designed zero field chamber achieves an internal magnetic field integral of 0.67 G·cm along the neutron path under the geomagnetic field condition.The maximum neutron depolarization for 0.4 nm neutrons is 0.76%,which sufficient for general polarization analysis application.The finite element method simulation results are examined by neutron Bloch equation dynamics simulations and in-lab measurement.Based on the established effective zero-field shielding design,we further discuss the relationship between magnetic field shielding and the dimensions of the device.The application of the device to spectrometers and the future improvement in the device structure are also discussed.
作者
曾滔
董雨晨
王天昊
田龙
黄楚怡
唐健
张俊佩
余羿
童欣
樊群超
Zeng Tao;Dong Yu-Chen;Wang Tian-Hao;Tian Long;Huang Chu-Yi;Tang Jian;Zhang Jun-Pei;Yu Yi;Tong Xin;Fan Qun-Chao(Key Laboratory of High Performance Scientific Computation,School of Science,Xihua University,Chengdu 610039,China;Institute of High Energy Physics,Chinese Academy of Sciences,Beijing 100049,China;Spallation Neutron Source Science Center,Dongguan 523803,China;University of Chinese Academy of Sciences,Beijing 100049,China;Sino-French Institute of Nuclear Engineering and Technology,Sun Yat-sen University,Zhuhai 519082,China)
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2023年第14期58-68,共11页
Acta Physica Sinica
基金
国家重点研发计划(批准号:2020YFA0406000)
国家自然科学基金(批准号:12075265,U2032219)
广东省基础与应用基础研究基金(批准号:2021B1515140016)
东莞市引进创新创业领军人才计划(批准号:20191122)
广东省自然科学杰出青年基金(批准号:2021B1515020101)资助的课题。
关键词
磁场屏蔽
极化中子技术
拉莫尔进动
有限元分析
magnetic field shielding
polarized neutron technique
Larmor precession
finite element analysis
