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精密测量地球表面的重力加速度(g, 常用值9.81 m/s2) 是探测地球重力场的重要途径, 已广泛应用于计量、测绘、地质、地震与资源勘探等领域. 随着我国2000国家重力基本网和中国地壳运动观测网络的建成, 对高精度绝对重力测量的需求日益增加. 为深入研究现有绝对重力测量技术可能存在的系统误差, 并满足国内多个领域对高精度绝对重力仪的迫切需求, 自主研制T-1型可搬运式高精度绝对重力仪样机, 采用经典的真空自由落体方案, 通过激光干涉测量和数据拟合方法获得重力加速度值. T-1型绝对重力仪主要包括以下几部分: 高真空度自由落体装置、小型化激光干涉测量装置、超低频垂直隔振系统、高速信号采集系统、仪器控制与数据处理系统. 绝对重力测量的长度基准为稳频He-Ne激光器, 时间基准为铷原子钟, 这两项现有基准的测量不确定度都优于1 10-9. 测试结果表明, T-1型绝对重力仪在12 h内重力测值的标准差可优于1 upGal (1 upGal = 10-8 m/s2), 测量结果的复现性优于3 upGal, 可实现微伽量级不确定度的精密重力测量, 有望在我国多个关键领域发挥重要应用.The accurate measurement of local gravitational acceleration (g, normal value 9.81 m/s2) is a key approach to the exploration of the gravitational field of the earth, and it has been applied in metrology, geodesy, geodynamics, seismology, and mineral exploration. With the plan of '2000 national gravity network' and 'China crustal motion observation network', highly precision gravity measurement will be increasingly required in the long term. In order to further investigate the possible systematic error of current absolute gravity measurement, and satisfy various requirements for highly accurate gravity observation, the T-1 absolute gravimeter prototype is designed and built at Tsinghua University. The T-1 instrument adopts the classic free-fall scheme to measure the g value by tracking the trajectory of a free-fall motion in vacuum with a laser interferometer. The T-1 absolute gravimeter consists of several sub-systems: high vacuum free-fall chamber, compact laser interferometer, low-frequency vertical vibration isolation, high-speed signal acquisition system, instrument control and data processing system. The length and time standards used in g measurement are stabilized He-Ne laser and rubidium atomic clock respectively. It's well known that both of the two standards have an uncertainty of less than 1 10-9. The practical gravity measurement results of T-1 absolute gravimeter give a standard deviation of the mean of less than 1 upGal (1 up Gal = 10-8 m/s2) in a typical observation within 12 h. And the reproducibility of less than 3 upGal is verified by repeatedly measuring gravity. The T-1 absolute gravimeter is a promising instrument by which highly accurate gravity measurement at a microgal level can be realized, and it is hopefully to be used in many research and application areas.
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Keywords:
- absolute gravity measurement /
- laser interferometer /
- free-fall method
[1] Faller J E 2002 Metrologia 39 425
[2] Wang L J 2009 Atom Optics and Space Physics (Amsterdam: IOS Press) p465
[3] Guo Y G, Huang D L, Fang Y Y, Zhang G Y, Zhou J H, Xu J Y 1988 Acta Geophysica Sinica 31 73 (in Chinese) [郭有光, 黄大伦, 方永源, 张光远, 周景华, 徐进义 1988 地球 31 73]
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[5] Origlia C, Quagliotti D, Berrino G, Corrado G, D'Errico V, Ricciardi G 2008 Annals of Geophysics 51 39
[6] Peter G, Moose R E, Wessells C W, Faller J E, Niebauer T M 1989 Journal of Geophysical Research 94 5659
[7] Niebauer T M, Sasagawa G S, Faller J E, Klopping F 1995 Metrologia 32 159
[8] Peters A, Chung K Y, Chu S 1999 Nature 400 849
[9] Xu X Y, Wang Y Z 1997 Acta Phys. Sin. 46 1062 (in Chinese) [徐信业, 王育竹 1997 46 1062]
[10] Zheng S L, Chen J, Lin Q 2005 Acta Phys. Sin. 54 3535 (in Chinese) [郑森林, 陈君, 林强 2005 54 3535]
[11] Ren L C, Zhou L, Li R B, Liu M, Wang J, Zhan M S 2009 Acta Phys. Sin. 58 8230 (in Chinese) [任利春, 周林, 李润兵, 刘敏, 王谨, 詹明生 2009 58 8230]
[12] Zhang W M, Wang Y, Zhou X H 2008 Progress in Geophysics 23 69 (in Chinese) [张为民, 王勇, 周旭华 2008 地球物理学进展 23 69]
[13] Liu D Z, Li H, Xing L L, Sun S A, Liu Z W, Xiang A M 2007 Journal of Geodesy and Geodynamics 27 88 (in Chinese) [刘冬至, 李辉, 邢乐林, 孙少安, 刘子维, 项爱民 2007 大地测量与地球动力学 27 88]
[14] Svitlov S, Maslyk P, Rothleitner C, Hu H, Wang L J 2010 Metrologia 47 677
[15] Svetlov S 1997 Gravity, Geoid and Marine Geodesy 117 (Berlin: Springer) 47
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[1] Faller J E 2002 Metrologia 39 425
[2] Wang L J 2009 Atom Optics and Space Physics (Amsterdam: IOS Press) p465
[3] Guo Y G, Huang D L, Fang Y Y, Zhang G Y, Zhou J H, Xu J Y 1988 Acta Geophysica Sinica 31 73 (in Chinese) [郭有光, 黄大伦, 方永源, 张光远, 周景华, 徐进义 1988 地球 31 73]
[4] Zhang W M, Zhang C J 2002 Progress in Geophysics 17 180 (in Chinese) [张为民, 张赤军 2002 地球物理学进展 17 180]
[5] Origlia C, Quagliotti D, Berrino G, Corrado G, D'Errico V, Ricciardi G 2008 Annals of Geophysics 51 39
[6] Peter G, Moose R E, Wessells C W, Faller J E, Niebauer T M 1989 Journal of Geophysical Research 94 5659
[7] Niebauer T M, Sasagawa G S, Faller J E, Klopping F 1995 Metrologia 32 159
[8] Peters A, Chung K Y, Chu S 1999 Nature 400 849
[9] Xu X Y, Wang Y Z 1997 Acta Phys. Sin. 46 1062 (in Chinese) [徐信业, 王育竹 1997 46 1062]
[10] Zheng S L, Chen J, Lin Q 2005 Acta Phys. Sin. 54 3535 (in Chinese) [郑森林, 陈君, 林强 2005 54 3535]
[11] Ren L C, Zhou L, Li R B, Liu M, Wang J, Zhan M S 2009 Acta Phys. Sin. 58 8230 (in Chinese) [任利春, 周林, 李润兵, 刘敏, 王谨, 詹明生 2009 58 8230]
[12] Zhang W M, Wang Y, Zhou X H 2008 Progress in Geophysics 23 69 (in Chinese) [张为民, 王勇, 周旭华 2008 地球物理学进展 23 69]
[13] Liu D Z, Li H, Xing L L, Sun S A, Liu Z W, Xiang A M 2007 Journal of Geodesy and Geodynamics 27 88 (in Chinese) [刘冬至, 李辉, 邢乐林, 孙少安, 刘子维, 项爱民 2007 大地测量与地球动力学 27 88]
[14] Svitlov S, Maslyk P, Rothleitner C, Hu H, Wang L J 2010 Metrologia 47 677
[15] Svetlov S 1997 Gravity, Geoid and Marine Geodesy 117 (Berlin: Springer) 47
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