精密扭秤实验中磁场梯度影响研究

Static magnetic field would contribute a very important systematic error source in precise torsion balance experiments. At present in many high precision torsion balance experiments, people only consider the effect of magnetic induction B, but had no analysis of magnetic gradient effect. However, by some preliminary analysis, the magnetic gradient field may produce a torque two order of magnitude higher than that of the thermal noise limit on torsion pendulum, which would be a potential source of systematic error in these experiments. In this project, we would focus on precise measurement of the environment magnetic gradients and magnetic quadrupole moment of torsion balance, and according to the measurement results, we can optimize the design of magnetic shielding. The residues torque acting on torsion pendulum after magnetic shielding was expected to be less than 10^-18Nm, lower than the contribution of thermal noise limit.

静磁场是精密扭秤实验中一个非常重要的干扰源，目前国内外许多高精度扭秤实验只考虑了磁感应强度B的影响，却没有分析磁场梯度的影响。经一些前期初步分析，磁场梯度对扭秤的影响可能会高于热噪声极限两个量级，是一个重要的潜在系统误差源。本项目希望通过采用精密扭秤技术，对实验环境的磁场梯度和扭秤的磁四极矩进行精密测量，从而能够定量评估磁场梯度对精密扭秤实验结果的影响，并根能跟据测量结果，优化磁屏蔽的设计方案。预期应用在使得磁场梯度对扭秤上的力矩能够小于10^-18Nm，低于热噪声极限。

本项目按照计划利用高精度扭秤测试系统完成实验背景磁场梯度的精密测量。在研究人工磁场的梯度场的产生方案的设计与误差分析之后，完成人工磁场梯度场的线圈绕制工作以及相关的检测工作；利用高精度扭秤测试系统，通过相关调制实验，完成矩型扭秤的磁四极矩测量；根据磁四极矩测量结果，并通过有限元等分析方法优化磁屏蔽设计。最终在华中科技大学引力实验中心弱等效原理检验实验中，磁场贡献的力矩噪声低于10^-18Nm，实现项目目标。