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.
- 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.