用于原子干涉测量的多段圆柱形磁屏蔽装置性能分析及实验研究

Performance analysis and experiment study on multi-sectional cylindrical magnetic shield device used for atom interferometric measurement

地磁场和环境杂散磁场在原子干涉测量过程中会引入测量噪声和系统误差,一般采用将磁屏蔽材料薄板卷曲后焊接成的圆筒逐段拼接起来,以制成足够长度的圆柱形磁屏蔽装置。为了明确这种方法对磁屏蔽性能的影响,详细分析了磁屏蔽层数、轴向及横向焊缝、两端面加盖引起的屏蔽区域剩磁场分布的变化,结果发现4 mm宽的轴向焊缝影响不大,而4 mm宽、相对磁导率较低的水平焊缝会产生明显的漏磁,两端面加盖能降低剩磁场强度但不能增大均匀磁场区域。根据分析结果制作了上抛式冷原子干涉重力仪中干涉区所使用的双层圆柱形磁屏蔽装置,实测结果表明,经退磁后获得的长度为700 mm、不均匀度小于4 nT的均匀磁场区域满足原子干涉测量的需求,与仿真分析也有较好的一致性。

The gravitational and environmental stray magnetic fields will introduce measurement noises and system errors during atom interferometric measurement process. Usually, the magnetic shield material sheets are rolled and welded to become the cylindrical segments, which are spliced to form the cylindrical magnetic shield device with enough length. To clarify the influence of this fabrication method on the magnetic shielding performance, the variations of residual magnetic field distribution in shielding area caused by the number of shield layers, the axial and transverse weld seams and adding caps on both ends of the shield device are analyzed in detail in this paper. The results show that the existence of the axial weld seam with the width of 4 mm has little influence on magnetic shielding, however the presence of the transverse weld seam with the width of 4 mm on the shield with lower relative magnetic permeability will introduce obvious magnetic flus leakage, adding caps on both ends of the shield device may reduce the residual magnetic field intensity, but it can hardly enlarge the region of uniform magnetic field. Based on the analysis results, a dual-layered cylindrical magnetic shield device used for the interference area of the upward-projectile cold atom-interferometry gravimeter was fabricated, and the actual measurement results reveal that a uniform magnetic field region with length of 700 mm and unevenness of 4 nT is obtained after demagnetization, which satisfies the requirements of atom interferometric measurement, and has good consistency with the simulation results.