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| The Preliminary Progress of Cold Atom Absolute Gravimeter at NIM |
| WANG Shao-kai1,ZHUANG Wei1,ZHAO Yang1,FANG Fang1,LI Tian-chu1,QIAN Jin2,HU Hua2 |
1. National Institute of Metrology, Beijing 100029, China
2. Department of Precision Instrument, Tsinghua University, Beijing 100084, China |
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Abstract The design process and preliminary progress of cold atom absolute gravimeter project in National Institute of Metrology is reported. In first step the design of vacuum physics part, laser-optics and control systems are completed, and now the three parts are working together. The cold atoms are prepared in two-dimensional magneto-optical trap (2D MOT), and three-dimensional magneto-optical trap (3D MOT), and fall freely from the center of 3D MOT while the Raman laser beams split, flip and recombine the wave packets during the process. The vacuum part, placed within two perm alloy magnetic shielding, has a pressure better than 5 × 10-8 Pa. Residual magnetic field strength inside the shield is less than 150 nT. Through comparing, a method is choosed to reduce vibration noise from the isolator siesmometer compensation and long-period spring methods. Co-axial symmetry detection method is used in order to reduce the influence of the Coriolis force on atom interferometric phase. To facilitate the evaluation of systematic error of Coriolis force, the vacuum system is placed on a rotating platform which can rotate 360° easily. About 108 cold atoms are cooled to a temperature of about 6 μK, and the free fall signal of cold atom with a signal to noise ration of 300 without state selection is got.
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| ［1］Louchet-Chauvet A, Farah T, Bodart Q, et al. The influence of transverse motion within an atomic gravimeter［J］. New journal of physics, 2011, 13(13):2007-2009. |
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2015, Vol. 36 
