Production, manipulation and cooling of a guided beam of ultracold atoms |
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ATOM LASER Thanks to RF outcoupling, it is already feasible to extract a coherent matter wave (Fig. 1) from a Bose-Einstein condensate (BEC). Coherent beams obtained in this fashion are nothing but pulsed atom lasers, pulsed in this sense means that one needs to achieve again and again BEC in order to manipulate the outcoupled beam. The major restriction for future developments is the available mean flux of atoms and the limited rate of repetition: actually, to achieve BEC one needs to load a magnetic trap, and then to perform forced evaporative cooling, which takes typically tens of seconds. By contrast, the goal of our experiment is to produce a continuous coherent beam of cold atoms, much more intense than those based on standard BEC. |
Fig.
1 : Atom laser gallery
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BASICS This
experiment, started in september 1999, consists in injecting pre-cooled
atoms into a magnetic guide, in order to implement evaporative cooling
along the guide. Our aim is to Bose condense atoms in the tranverse
ground state of the guide, realizing a monomode beam. This kind of
source enables the study of superfluidity in reduced-dimension traps
and paves the way for future applications such as nanolithography,
metrology,... In figure 2, we summarize different regimes in terms of
brightness and phase space density obtained so far for cold atomic
beams, where the path when evaporative cooling is applied is marked in
green. |
Fig 2 : Brightness as a function of phase space density. |
PRELIMINARY STUDIES Preliminary
theoretical studies have
been done by our group, they mainly show that a
significant gain in brightness is reachable for a magnetic guide of a
few meters. Moreover, longitudinal coherence is induced by interactions
and can be significantly higher than the de Broglie wavelength. Note
furthermore that the expected output flux is of the order of 107
atoms/s, higher by more than two or three orders of magnitude with
respect to
the mean flux obtained from traditional BEC.
Ref.: Evaporative cooling of an atomic beam, E. Mandonnet, A. Minguzzi, R. Dum, I. Carusotto, Y. Castin, and J. Dalibard, Eur. Phys. J. D 10, 9 (2000). |
We acknowledge funds supporting our activity |
Last update : september 26th (2007) | webmaster : dgo (at)
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