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Refroidissement et piégeage d'atomes de chrome

Abstract : This work comes within the scope of obtaining dipolar quantum gases : a Bose-Einstein
condensate of 52Cr and a Fermi sea of 53Cr. The large magnetic moment of 6 µB in the ground state,
the electronic structure in lambda-shape and the presence of a fermionic isotope made chromium attractive
for experiments in the field of ultracold atoms.
The experimental setup constructed looks like a trapping experiment on a usual element. Nevertheless,
specific technical solutions to operate a high-temperature oven or to generate a blue laser
beam at 425.5 nm which is not modulated were chosen. Moreover, two projects which I have carried
out are detailed : the temperature lock of a Fabry Perot cavity and the absorption optics system.
The magneto-optical traps of 52Cr and 53Cr obtained contain respectively 4x10^6 and 5x10^5 atoms
for densities of 8x10^10 and 2.5x10^10 cm−3. These two traps have similar characteristics : a high inelastic
two-body collision rate in the range of 5x10^−9 cm^−3.s^−1 and a one-body loss rate of 169 s^−1 for the
52Cr and of 280 s^−1 for the 53Cr explained by a decay towards metastable states. This latest property
enables to accumulate continuously 2x10^7 atoms of 52Cr and 8x10^5 atoms of 53Cr in the quadrupolar
trap formed by the coils of the magneto-optical trap. The first achievement and characterization of a
simultaneous magneto-optical trap of a mixture 52Cr-53Cr is also shown.
The accumulation of bosonic metastable atoms in an optical trap superimposed to a linear magnetic
trap is studied. This original trap enables to achieve the first optical trap of atoms in metastable
states. In a very short time of 100 ms, the optical trap contains 1.2x10^6 metastable atoms with a
density of 10^11 cm^−3. This result constitutes a fist step towards the realization of a crossed optical
trap where atoms will be polarized and then cooled below the condensation threshold.
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Contributor : Arnaud Pouderous <>
Submitted on : Friday, August 31, 2007 - 11:00:36 AM
Last modification on : Saturday, February 15, 2020 - 1:50:13 AM
Long-term archiving on: : Thursday, April 8, 2010 - 9:33:53 PM

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Arnaud Pouderous. Refroidissement et piégeage d'atomes de chrome. Physique Atomique [physics.atom-ph]. Université Paris-Nord - Paris XIII, 2007. Français. ⟨tel-00169009⟩

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