【作者】 王晴岚；

【导师】 罗俊； 邵成刚；

【作者基本信息】 华中科技大学 ， 精密测量物理， 2012， 博士

【摘要】 牛顿反平方定律作为引力理论的基石之一,描述了小到日常物品大到天体间的相互作用,但在极小范围内它的正确性并没有得到足够高的验证。除此之外,自然界还存在着其他基本相互作用,趋于最朴素的想法,物理学家们致力于寻找一个统一理论去包含所有的相互作用形式。在漫漫统一路途上,出现了如等级问题、宇宙常数问题需要填补的鸿沟。由此提出的弦理论、膜世界理论、M理论等频频预言着额外维的存在,反平方定律在一定范围内将出现破缺。近些年物理学界对反平方定律的实验检验充满了关注,不断刷新的破缺上限也使人们对寻找额外维充满了期待。根据ADD理论中提出的大尺度额外维,当额外维数目n=2时,反平方定律会在亚毫米范围发生破缺,这也使得国际上众多研究小组在这个区间展开高精度的实验检验。扭秤作为极端精密测量工具,在弱力检测领域有着重要的地位,本实验室对扭秤的长期研究及使用为开展反平方定律检验提供了良好的基础。采用间距调制的原理,将扭秤作为检验质量,周期性地改变它与吸引质量之间的间距,测量非牛顿信号的大小。调制过程中,通过合理的设计补偿掉牛顿力矩变化,使实验成为一个“零”检验。本实验室于2007年,在间距176μm-343,um范围内,对检验质量与吸引质量的牛顿力矩补偿水平达到(0.2±2.1)×10-16Nm水平,在95%的置信水平上,给出反平方定律的破缺上限为|α|≤1时,λ≤66μm,能量的统一标度M*≥2.8Tev/c2,该结果非常接近国际上的最好结果。为了能在更高精度上开展实验,进行了以下几点主要改进：1)检验质量与吸引质量之间的间距变化减小到120μm-240μm,提高非牛顿力的强度；2)减少装置中的零散部件,提高定位安装精度,使牛顿力矩的补偿水平提高至10-17Nm量级；3)将调制信号的频率选取在高频区域,提高扭秤的探测灵敏度。基于上述改进,“零”实验的结果可望将当前的最好上限提高一个量级。经过两年的准备,实验于2010年底完成了整体的搭建,并进行了初步的间距调制实验,但在调制频率处实验探测到了非常明显的信号。在排除掉牛顿力矩的影响,并根据当前非牛顿力的上限排除掉它的可能性,经过大量的实验分析,得出干扰信号产生的最主要来源为静电效应。目前正在对静电屏蔽装置、地线干扰、仪器电源波动等进行相应的研究及改进,为下一阶段再次进行间距调制实验而准备。本课题为国家重点研究发展计划(批准号：2010CB832802)的资助。更多还原

【Abstract】 The inverse-square law is a fundamental of theories of gravity, impressively demonstrated from astronomical scales to sub-millimeter scales. However, due to difficulties associated with designing sensitive short-range experiments, the range below1mm was mostly unexplored until a few years ago. Besides that, there are other three fundamental interactions. Connecting gravity with the rest of physics is clearly the central challenge of physics. In an attempt to solve some of the greatest puzzles in physics, namely, the hierarchy problem, the comsmological constant problem, many modern theories of gravity, including string, brane-world theories and M-theories, suggest the existence of extra dimensions. The gravitational force will deviate from Newtonian inverse-square law. In ADD formalism, if the number of extra dimensions is two, it is hoped to find the deviation of inverse-square law in submillmeter range.Torsion pendum as the extreme precision measuring tool in extremely weak force detection plays an important role. By using the torsion pendulum as a test mass, modulate the distance between the test mass and source mass to test the non-Newtonian force. Design a counterbalance mass to decrease the Newtonian force, and such experimental design is so-called null test for the expected signal. In the year2007, we finished experiment in the range176μm～343μm, the results disclosed that the upper limit on non-Newtonian force was λ≤66μm when|a|≤1and the uniform energy M’≥2.8Tev/c2. The net change of the Newton’s torque in experimental range is (0.2±2.1)x10-16Nm. The result nearly reaches the best limit in the world.This thesis describes our improved experiment. Three main improvements have been made to elevate the sensitivity of our torsion pendulum compared with previous by one order. First, the minimal surface separation between test and source mass can be approached as close as120μm by using a thinner electrostatic shielding membrane. Second, the Newtonian gravitational perturbations, due to the modulating motions of the source mass and its supporting glass masses from120μm to240μm, are precisely balanced to the amplitude of10-17Nm. Third, the higher frequencies (than the free oscillation of torsion pendulum) are chosen for the dual modulation of both the expected signal and the calibration gravitational torque. In the latest two years, we have got the preliminary results. The amplitude of the signal is not exactly as we expecte. After lots of experiments, we suppose that the signal is due to the electrostatic effect. Now we are focusing on the improving the electrostatic shielding, decreasing the ground disturbance and the voltage fluctuations on the wires.This work is supported by the National Basic Research Program of China (No.2010CB832802).更多还原