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Evaporation par radio-fréquence et condensation de bose-Einstein d'un gaz d'alcalins en régime de champ fort.

Bruno Desruelle 1
1 laboratoire Charles Fabry de l'Institut d'Optique / Optique atomique
LCFIO - Laboratoire Charles Fabry de l'Institut d'Optique
Abstract : We present a new tool for Bose-Einstein condensation using evaporative cooling of magnetically trapped alkali atoms. Our approach is based on the use of ferromagnetic materials to generate the trapping potential. It allows us to obtain a strong confinement at low electrical power (100 W). A preliminary experiment allowed us to validate the ,use of an ironcore electromagnet for magnetic trapping of neutral atoms. We then developed a second generation ofelectromagnet to experimentally study evaporative cooling ofa rubidium 87 gas. A specific feature ofthis setuP is that the atoms are trapped in a high magnetic field, of order 100 Gauss. Beacuse of this high magnetic field, the quadratic Zeeman effect is not negligible and radio-frequency transitions between adjacent Zeeman sublevels are not resonant at the same place. This has dramatic consequences on evaporative cooling in the F=2 state and leads to an interruption of the evaporation process. This was verified through an evaporation experiment with a fixed RF frequency. We also observed that evaporative cooling of a gas trapped in F=m=2 does not allow to cool the atoms below 50 J.!K. On the contrary, the evaporation process is not adversely affected by the quadratic Zeeman effect for the other hyperfine state F=l and we were able to reach Bose-Einstein condensation by cooling the atomic cloud below 150 nK.
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Submitted on : Monday, July 9, 2012 - 4:39:30 PM
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Bruno Desruelle. Evaporation par radio-fréquence et condensation de bose-Einstein d'un gaz d'alcalins en régime de champ fort.. Optique [physics.optics]. Université Paris Sud - Paris XI, 1999. Français. ⟨pastel-00716029⟩

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