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 &times 10⁴.

Atom: ¹³³Cs, |F=3, m_F = +3>

Trap: Levitated crossed dipole trap.

Method:

• 2 &times 10^{8 87}Rb atoms in |1,-1> and 2 &times 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 &microK and PSD ~ 10^-7.
• RF evaporation of the Rb atoms enables the sympathetic cooling of Cs. After 38 seconds of RF evaporation: N_Rb ≈ 4.0 &times 10⁷, N_Cs ≈ 1.4 x 10⁷, T ≈ 60 &microK 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 &microK 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.