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Implémentation d'une source d'atomes ultra-froids pour l'amélioration de l'exactitude d'un gravimètre atomique

Abstract : This thesis aims to improve the accuracy of the Cold Atom Gravimeter from LNESYRTE.This gravimeter employs atom interferometry techniques to measure the local gravityacceleration g of free falling Rubidium 87 cold atoms. This gravimeter is the national metrologicalreference meaning that all its biases must be evaluated with the lowest uncertainties. At the beginningof this thesis, the total accuracy budget of 4.3μGal was dominated by the uncertainty onthe wavefront aberration bias which accounted for 4.0μGal. In order to improve the evaluation ofthis effect, we implemented an ultra-cold atom source, with which we performed g measurementsover a wide range of temperatures. The developpment of a complete model of the experiment anda simulation of the impact of the wavefronts on the g measurements allowed us to gain insightson the evaluation of this bias which uncertainty was thus improved by a factor three and is now1.3μGal. Finally the gravimeter participated in the Kibble balance project which goal was tolink the Planck constant to the kg unit. This project needed the determination and transfer ofthe absolute g value. We contributed to the revolution of the International System of Units : thePlanck constant is now fixed and the definition of the kg is modified. This new definition is noweffective since 20 May 2019.
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Romain Karcher. Implémentation d'une source d'atomes ultra-froids pour l'amélioration de l'exactitude d'un gravimètre atomique. Physique Atomique [physics.atom-ph]. Sorbonne Université, 2019. Français. ⟨NNT : 2019SORUS165⟩. ⟨tel-02950853⟩

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