扭秤检验牛顿反平方定律新方案研究

Short range tests of the Newton's Gravitational Inverse-Square Law are interesting from several quite different perspectives. Recent attempts at unifying the descriptions of gravity and quantum mechanics predict that Newton's Gravitational Inverse-Square Law will fail below some distance scale, possibly as large as 1mm. Recent measurements of the Dark Energy content of the universe could also imply short-range modifications to gravity. In China, Huazhong University of Science and Technolgy(HUST)in 2007 and 2012, respectively, in the sub-mm, mm range, using the torsion balance with separation-modulation to test the inverse-square law (ISL). The null results achieve the international advanced level. In order to improve the precision of the experiment, we will propose a new torsion balance experimental design. The dominant problem in testing gravitation at short range, is the extreme weakness of gravity. This forces the experimenter to adopt design that maximize the signal and minimize the noise and backgrounds. We will focuse on the noise limit,such as noise limit and measurement noise. Electromagnetic interactions between the test bodies are the primary source of background signals. The new design will distinguish the electromagnetic signal and the non-newtoian force signal, and reduce the impact of the electromagnetic noise effectively. The Newtonian torque and the detection sesitivity in the design will improve to 10^(-18)(Nm), while the experiment base on it can raise the limit of the violation of the inverse-square law by 1 to 2 orders of magnitude.

近距离牛顿反平方定律的实验检验一直是国际上的研究热点与难点，它不仅能为"大统一"理论提供直接的实验依据、寻找预言中的轴子等，也为精密测量技术本身做出贡献。国内的华中科技大学引力实验中心也分别于2007及2012年在亚毫米、毫米区间，利用扭秤间距调制的原理进行了检验，其结果处于国际领先水平。为了能在更高精度上进行实验，本课题将提出新的扭秤密实验方案。我们将分别从扭秤探测中受到的各项基本噪声限制、当前实验遇到的主要干扰项-电磁效应、牛顿力矩的补偿等方面进行有针对的研究。通过合理的设计，使牛顿力矩的效应及扭秤的探测灵敏度达到10^(-18)Nm水平，同时有效降低电磁效应的影响，该方案在亚毫米区间的实验结果可将当前的国际最好上限提高1~2个数量级。

本项目完成了扭秤检验近距离牛顿反平方定律的新方案设计，与目前国内采用以间距调制思路的不同之处在于，我们以密度调制为出发点，控制检验质量与吸引质量之间的间距为固定值，测量两个平板之间非牛顿效应的法向分量，大幅减少因间距改变而引入的静电干扰。同时采用多重对称的设计，控制牛顿效应的影响在5e-18Nm水平，区分了转台驱动频率与待测信号频率，有效减少外界干扰。同时对悬挂扭秤和测量装置进行了噪声分析，确保整个实验装置能在高灵敏度下进行非牛顿信号的探测。整个方案可将作用程为200微米处的当前牛顿反平方上限提高一个量级，随后开展的相关实验也验证了该设计的正确性。