Investigation Of The Electrostatic Force Contribution In The Short Range Test Of Non-newtonian Forces

In classical electrodynamics, it is generally believed that a conductor is an equipotential body, and the surface potential of a conductor is identical. However, along with the development of measurement technology, people gradually found there are potential differences on the surface of conductor. It is caused by the differences in the physical and chemical properties and the impact of environment. This phenomenon is called patch effect, which changes the electrostatic force between conductors, and becomes an important background noise in short range and high precision gravity experiments.The test of non-Newtonian forces is aimed to verify the Newtonian Gravitational Inverse Square Law(ISL) with high precision and obtain the constrains on the deviations. With the continuous improvement of experimental precision, people found obvious electrostatic interaction due to the patch effect, becomes an important error in this kind of experiments. In order to obtain better upper constrains on the deviation of ISL, we may need to find accurate and effective method to evaluate the contribution of the patch electrostatic force in the experiment.At present, many groups have established various models to calculate the patch electrostatic force. However, these models do not give accurate and rigorous results. In addition, the calculation methods are so complicated that cannot be applied to the analysis of experimental data.In this thesis, we mainly use the finite element method to calculate the spatial distribution of electrostatic force signal in the test of non-Newtonian forces, which based on the measurement of the conductor surface potential. When comparing the calculated results with the experimental measured signal, we found their distribution patterns are the same in general, but cannot match to each other. To understand the mismatch, we analyze the potential measurement method used in our experiment. We find the measured result of this method is not accurate, and we think the inaccuracy of potential measurement leads to deviation when we evaluate electrostatic force signal. It is why the calculated electrostatic force doesn't coincide with the experimental signal. Based on these analyses, we proposed that we may measure the surface potential by a conventional Kelvin probe whose system error is small. In addition, we need to make marks on the surface of source mass so that we can perform the non-Newtonian force test at the exact same region where the surface potential is measured.