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Construction d'une fontaine double à atomes froids de 87Rb et 133Cs ; Etude des effets dépendant du nombre d'atomes dans une fontaine

Abstract : The definition of the second is based on the cesium atom. To date the best clocks are cold cesium atom fountains. They realize the second with an accuracy of 10^{-15}. Their stability, ultimately limited by quantum projection noise, is typically 6 x 10^{-14}\tau^{-1/2} for
4 x 10^5 detected atoms, and reaches 6 x 10^{-16} after 3 hours of integration. In these conditions the interactions between cold atoms shift the clock frequency by about 3 x 0^{-14}. Technically it is difficult to correct this shift at the 10^{-16} level. This PhD report shows that
^{87}Rb is an interesting alternative to Cs, since its collisional shift is nearly 100 times lower. Firstly we caracterize the performance of the ^{87}Rb fountain that we have constructed during this thesis. Then we model the atom number dependent effects in fountains: the collisional shift and the frequency pulling by the microwave cavity. Both effects are measured simultaneously using a differential method. Modeling the atomic cloud evolution in the fountain allows us to compare our measurements with the theoretical predictions for the s-wave scattering lengths. Comparing the hyperfine frequencies of Rb and Cs in independent fountains allows us to test the drift of the fine structure constant \alpha at the level of 7 x 10^{-15}.year^{-1}. In order to
improve this test we have constructed a dual fountain that can operate with both Rb and Cs. The technical improvements made to this fountain, together with a new procedure for measuring the collisional shift of Cs, should allow us to explore the 10^{-16} range of accuracy for both alkalis.
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https://tel.archives-ouvertes.fr/tel-00001065
Contributor : Yvan Sortais <>
Submitted on : Wednesday, January 30, 2002 - 3:56:49 PM
Last modification on : Thursday, December 10, 2020 - 12:37:09 PM
Long-term archiving on: : Friday, April 2, 2010 - 6:08:50 PM

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  • HAL Id : tel-00001065, version 1

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Yvan R. P. Sortais. Construction d'une fontaine double à atomes froids de 87Rb et 133Cs ; Etude des effets dépendant du nombre d'atomes dans une fontaine. Physique Atomique [physics.atom-ph]. Université Pierre et Marie Curie - Paris VI, 2001. Français. ⟨tel-00001065⟩

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