基于静电控制扭摆方案的导体表面电势测量研究

The temporal and spatial variation of surface potential on the conductor, often called Patch effect, has been identified as a significant error source in terrestrial or spaceborn gravitational experiments. In GP-B mission proposed by Stanford University and LISA mission, the Patch effect is one of the largest noise contributors. Therefore, it is significant to investigate the Patch effect. In this item, we propose an electrostatic-controlled torsion pendulum to investigate the Patch effect on conductor. This scheme will combine the scanning capability of the Kelvin probe and the high sensitivity of the torsion pendulum base on the high-precision electrostatic controlled torsion pendulum, in order to measure the distribution of surface potential on conductor with high precision. It expects that the resolution of measuring can achieve 10μV/Hz^1/2 and its spatial resolution achieve 0.1mm order of magnitude. Base on this apparatus, we can explore the physical mechanism of the Patch effect to provide guidance for high precision gravitational experiments on ground or space.

导体表面电势随时间的涨落变化和随空间的非均匀分布称之为Patch效应，该效应是地面和空间高精度引力实验中重要的误差源。在美国斯坦福大学的引力探针GP-B实验和空间引力波探测LISA计划中Patch效应都是最主要噪声来源之一，因此研究Patch效应的产生机理及其抑制方法具有重要的科学意义和应用背景。本项目提出了一种静电控制扭摆系统来研究导体表面的Patch效应。该方案将基于高精度静电控制扭摆系统，结合Kelvin探针方案扫描测量和传统扭秤方案高灵敏度的特点，来实现对导体表面电势分布的精确测量。该系统预计在空间分辨率0.1mm量级上测量精度达到10微伏/Hz^1/2。基于该系统我们可开展Patch效应物理机制的探索研究，为地面和空间的高精度引力实验研究提供指导。

本项目我们提出了一种静电扭摆方案来测量导体表面电势随时间的波动以及其空间分布。项目期间按照设计搭建了一套静电扭摆系统，并且基于该系统实现了弱力测量与执行机标定技术。目前本系统的导体表面电势测量精度为0.5mV/Hz^1/2，主要受限于自准直仪的分辨率水平。拟采用高精度的电容位移传感方式进一步提高电势测量精度。导体表面电势测量技术与高精度扫描技术仍在实验中。该系统实现了探针的悬挂，放宽了实现系统对待测样品的限制，为今后开展对Patch效应的研究提供了高效的平台。现在实验主要完成了原理性验证，为后续继续开展深入的研究奠定了基础。