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冷原子团的高斯半径和温度是用来描述冷原子团, 反映冷原子特性的主要参数. 本文提出了一种新型的测量冷原子团高斯半径和温度的方法, 采用过饱和近共振激光束照射冷原子团, 原子由于吸收了光子动量偏离原来的运动轨道, 而不能被探测系统所探测. 根据冷原子团的原子分布规律, 理论上构建了物理模型, 通过改变作用于冷原子团的推除光的尺寸来控制被推除的冷原子数目, 计算得到了不同高斯半径的冷原子团剩余原子数目与推除光尺寸的关系. 以国家授时中心铯原子喷泉为实验平台, 利用横向偏置的刀口光阑在不同下落高度控制作用于冷原子团的推除光尺寸, 测量出不同高度的剩余原子数目随推除光尺寸的变化情况. 应用理论公式拟合实验数据, 最终得到冷原子团在磁光阱中心正下方10 mm和160 mm处的高斯半径分别为(1.54 ± 0.05) mm和(3.29 ± 0.08) mm, 进一步计算得到冷原子团温度为(7.50 ± 0.49) μK. 为了验证刀口法的准确性和可重复性, 在同一实验条件下用刀口法和飞行时间法对冷原子团温度进行了测量与对比, 最终得到两种方法的测量结果基本一致.
The Gaussian radius and temperature of cold atomic cloud are important parameters in describing the state of cold atoms. The precise measuring of these two parameters is of great significance for studying the cold atoms. In this paper, we propose a new method named knife-edge to measure the Gaussian radius and temperature of the cold atomic cloud. A near-resonant and supersaturated laser beam, whose size is controlled by a knife-edge aperture, is used to push away the cold atoms in the free falling process of cold atomic cloud. By detecting the intensity of fluorescence signal, the numbers of residual atoms under different-sized near-resonant beams can be obtained. According to the characteristic of cold atoms′ distribution, we construct a theoretical model to derive the Gaussian radius of cold atomic cloud from the recorded residual atom number and near-resonant beam size. Since the Gaussian radius and temperature of cold atomic cloud are associated with each other, we can finally obtain the temperature of cold atomic cloud through the recorded residual atom number and beam size. By using this method, we successfully measure the Gaussian radii of cold atomic cloud at the heights of 10 mm and 160 mm below the center of 3D-MOT (three dimensional magneto-optical trap) to be (1.54 ± 0.05) mm and (3.29 ± 0.08) mm, respectively. The corresponding temperature of cold atomic cloud is calculated to be (7.50 ± 0.49) μK, which is well consistent with the experimental result obtained by using the time-of-flight method under the same condition. This experiment is conducted on the platform of Cesium atomic fountain clock of National Time Service Center, China. [1] 王义遒 1998 物理 27 131
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Zhang S L 2010 Ph. D. Dissertation (Anhui: University of Science and Technology of China) (in Chinese)
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图 1 刀口法测量冷原子团温度模型
Fig. 1. The model of measuring the temperature of cold atomic cloud by knife-edge method.
图 2 不同高斯半径的剩余原子数与刀口位置关系
Fig. 2. The residual atom number versus knife-edge position with different Gaussian radii.
图 3 刀口法测量冷原子团温度实验装置简图
Fig. 3. The schematic diagram of experimental setup for measuring cold atomic cloud´s temperature by knife-edge method.
图 4 磁光阱中心正下方10 mm (a)和 160 mm (b)处的剩余原子数与刀口位置关系
Fig. 4. The residual atom number versus knife-edge position at height 10 mm (a) and 160 mm (b)under the center of magneto-optical trap.
图 5 冷原子团自由下落飞行时间信号
Fig. 5. The cold atomic cloud´s time-of-flight signal in free falling process.
图 6 刀口法与飞行时间法测量冷原子团温度对比
Fig. 6. The comparison between knife-edge and time of flight methods in measuring cold atomic cloud´s temperature
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[1] 王义遒 1998 物理 27 131
Google Scholar
Wang Y Q 1998 Physics 27 131
Google Scholar
[2] 詹明生 2002 中国科学院院刊 17 407
Zhan M S 2002 BCAS 17 407
[3] 张少良 2010 博士学位论文(合肥: 中国科学技术大学)
Zhang S L 2010 Ph. D. Dissertation (Anhui: University of Science and Technology of China) (in Chinese)
[4] Liu H, Zhang X, Jiang K L, Wang J Q, Zhu Q, Xiong Z X, He L X, Lv B L 2017 Chin. Phys. Lett. 34 020601
Google Scholar
[5] Bauch A 2005 Metrologia. 42 S43
Google Scholar
[6] 卢向东, 李同保, 马艳, 汪黎栋 2009 58 8205
Google Scholar
Lu X D, Li T B, Ma Y, Wang L D 2009 Acta Phys. Sin. 58 8205
Google Scholar
[7] Zhuang Y X, Shi D T, Li D W, Wang Y G, Zhao X N, Zhao J Y, Wang Z 2016 Chin. Phys. Lett. 33 040601
Google Scholar
[8] Liu K K, Zhao R C, Gou W, Fu X H, Liu H L, Yin S Q, Sun J F, Xu Z, Wang Y Z 2016 Chin. Phys. Lett. 33 070602
Google Scholar
[9] Liu C, Zhou S, Wang Y H, Hou S M 2017 Chin. Phys. B 26 113201
Google Scholar
[10] 林弋戈, 方占军 2018 67 160604
Google Scholar
Lin Y G, Fang Z J 2018 Acta Phys. Sin. 67 160604
Google Scholar
[11] Wang Y B, Yin M J, Ren J, Xu Q F, Lu B Q, Han J X, Guo Y, Chang H 2018 Chin. Phys. B 27 023701
Google Scholar
[12] 王谨, 詹明生 2018 67 160402
Google Scholar
Wang J, Zhan M S 2018 Acta Phys. Sin. 67 160402
Google Scholar
[13] 吴长江, 阮军, 陈江, 张辉, 张首刚 2013 62 063201
Google Scholar
Wu C J, Ruan J, Chen J, Zhang H, Zhang S G 2013 Acta Phys. Sin. 62 063201
Google Scholar
[14] 阮军, 王叶兵, 常宏, 姜海峰, 刘涛, 董瑞芳, 张首刚 2015 64 160308
Google Scholar
Ruan J, Wang Y B, Chang H, Jiang H F, Liu T, Dong R F, Zhang S G 2015 Acta Phys. Sin. 64 160308
Google Scholar
[15] 王义遒, 王庆吉, 傅济时, 董太乾 1986 量子频标原理(北京: 科学出版社) 第552页
Wang Y Q, Wang Q J, Fu J S, Dong T Q 1986 Principle of Quantum Frequency Standard (Beijing: Science Press) p552 (in Chinese)
[16] 王义遒 2007 原子的激光冷却与陷俘(北京: 北京大学出版社) 第171页
Wang Y Q 2007 Laser Cooling and Trapping of Atoms (Beijing: Peking University Press) p171 (in Chinese)
[17] 韩燕旭, 王波, 马杰, 校金涛, 王海 2007 量子光学学报 13 30
Google Scholar
Han Y X, Wang B, Ma J, Xiao J T, Wang H 2007 Acta Sin. Quant. Opt. 13 30
Google Scholar
[18] 吴艳 2005 硕士学位论文(杭州: 浙江大学)
Wu Y 2005 M. S. Thesis (Hangzhou: Zhejiang University) (in Chinese)
[19] Chu S, Hollberg L, BjorkholmJ E, Cable A, AshkinA 1985 Phys. Rev. Lett. 55 48
Google Scholar
[20] Lett P D, Watts R N, Westbrook C I, Phillips W D, Gould P L, Metcalf H J 1988 Phys. Rev. Lett. 61 169
Google Scholar
[21] 程成, 曾凤, 程潇羽 2009 光学学报 29 2698
Cheng C, Zeng F, Cheng X Y 2009 Acta Opt. Sin. 29 2698
[22] 陈帅 2004 博士学位论文(北京: 北京大学)
Chen S 2004 Ph. D. Dissertation (Beijing: Peking University) (in Chinese)
[23] Walhout M, Sterr U, Orzel C, Hoogerland M, Rolston S L 1995 Phys. Rev. Lett. 74 506
Google Scholar
[24] 耿涛, 闫树斌, 王彦华, 杨海菁, 张天才, 王军民 2005 54 5104
Google Scholar
Geng T, Yan S B, Wang Y H, Yang H J, Zhang T C, Wang J M 2005 Acta. Phys. Sin. 54 5104
Google Scholar
[25] 王心亮 2017 博士学位论文(北京: 中国科学院大学)
Wang X L 2017 Ph. D. Dissertation (Beijing: University of Chinese Academy of Sciences) (in Chinese)
[26] Wynands R, Weyers S 2005 Metrologia 42 S64
Google Scholar
[27] Brzozowski TM, Maczyńska M, Zawada M, Zachorowski J, Gawlik W 2002 J. Opt. B: Quantum Semiclass. Opt. 4 62
Google Scholar
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