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Accurate Calculation of the Height of Cold Atoms Throw-Up
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摘要: 冷原子的上抛高度是上抛顶点至上抛起点的距离，铯原子喷泉钟实验中，向上光向下光频率失谐形成的移动光学黏胶使冷原子团进行了短暂的加速和匀速向上运动。激光关闭后，冷原子团在重力作用下，上抛至顶点然后自由落体至探测区从而被探测光探测。之前的计算忽略了冷原子团的加速和匀速向上运动过程，存在一定的系统误差。结合原子飞行信号实验数据，还原冷原子的三种不同运动过程，精确计算了冷原子的上抛高度，修正了原有的系统误差。Abstract: After the laser trapping and cooling, the cold atoms in a cesium fountain clock undergo a short period of upward acceleration and uniform motion due to the frequency detuning of the upward and the downward lasers. Then, with the cooling laser shut down, the cold atoms keep going up to the apex under the gravity and then fall down to the detection area to be detected by the detection laser. The height of cold atoms throw-up is the distance from the MOT center to the apex. Previous calculations ignored the acceleration and uniform upward movement of the cold atoms, resulting in a systematic error. This paper corrects for the error by considering three different movement processes of the cold atoms and accurately calculates the height of the cold atoms throw-up from the experimental data of the time-of-flight signal.
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Key words:
- cold atoms /
- fountain clock /
- height of throw-up /
- time-of-flight signal /
- accurate calculation
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图 1 计算高度差值与方法0计算高度的关系
Figure 1. Height differences (method 1 - method 0 and method 2 - method 0) versus the height calculated using method 0
表 1 不同方法计算得到上抛高度值 /（mm）
Table 1. Height values calculated using different methods /（mm）
方法0 方法1 方法2 550.0 562.1 557.9 560.0 572.0 568.0 570.0 582.2 578.0 580.0 591.8 588.1 590.0 602.0 598.2 600.0 612.4 608.2 610.0 622.4 618.3 620.0 632.3 628.4 630.0 642.2 638.4 640.0 652.3 648.5 650.0 662.4 658.6 660.0 672.6 668.6 670.0 682.7 678.7 680.0 692.6 688.8 690.0 702.7 698.8 700.0 712.8 708.9 710.0 722.8 719.0 720.0 732.9 729.0 730.0 743.0 739.1 740.0 753.0 749.1 750.0 763.3 759.2 760.0 773.2 769.3 770.0 783.1 779.3 780.0 793.2 789.4 790.0 803.3 799.4 800.0 813.3 809.5 810.0 823.4 819.6 
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