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Cesium BEC at Durham University

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Group: Cornish

Authors and contributors: D. J. McCarron, D. L. Jenkin, M. P. Koppinger, H. W. Cho and S. L. Cornish

Figure 1: False-color plots of the Bose-Einstein condensation of Cs in a crossed dipole trap. The atom number in the BEC is ~ 4 × 104.

Atom: 133Cs, |F=3, mF = +3>

Trap: Levitated crossed dipole trap.

Method:

  • 2 × 108 87Rb atoms in |1,-1> and 2 × 107 Cs atoms in |3,-3> are loaded into a magnetic quadrupole trap from a UHV MOT. Axial field gradient = 187 G/cm, T ≈ 160 µK and PSD ~ 10-7.
  • RF evaporation of the Rb atoms enables the sympathetic cooling of Cs. After 38 seconds of RF evaporation: NRb ≈ 4.0 × 107, NCs ≈ 1.4 x 107, T ≈ 60 µK and PSD ~ 10-5.
  • 15% of the Cs atoms are transferred into a crossed dipole trap by ramping the axial field gradient down to 29 G/cm. Here T = 10 µK and PSD ~ 10-2.
  • Simultaneously the spin is adiabatically flipped into |3,+3> and a bias field of 22.7 G is applied.
  • Evaporative cooling, by reducing the power of the dipole trap beams and then increasing the axial field gradient to 34 G/cm, over 17 seconds enables us to reach BEC.
  • The onset of BEC is observed with N ~ 105. The pure condensate atom number ~ 4 x 104.


    Figure 2: The team from L to R: Michael Koppinger, Hung Wen Cho, Daniel Jenkin, Simon Cornish and Danny McCarron.

Posted: 05 Jul 2010     Date: 09 Jun 2010



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