Atom Optics latest results

Evaporative cooling to BEC (24/02/04)


BEC was observed for the first time at UQ on the morning of Friday 20th February 2004.  This is only the second BEC in Australia, and the third in the southern hemisphere, behind the group of Andrew Wilson at the University of Otago in New Zealand and the group of John Close at the Australian National University.  
BEC at UQ

These are false colour absorption images of the atom cloud after 10ms of ballistic expansion.  From left to right the final RF frequency of the evaporative cooling ramp was 580, 575 and 570kHz.  The atom numbers are 6 x 10^4, 4 x 10^4, and finally 2 x10^4 atoms in a nearly pure condensate.  We estimate the transition temperature was about 250nK.

Below are images of the atoms in the magnetic trap at various stages through the evaporative cooling ramp.

Magnetically trapped atoms

Absorption image of atoms in the compressed magnetic trap. N = 2 x 10^7, T = 240 microKelvin




RF 3MHz

Part way through the evaporation (13MHz -> 3 MHz),
N = 3 x 10^6, T = 50 microKelvin




RF 1MHz

Further into the RF sweep (13Mhz -> 1MHz),
N = 7 x 10^5, T = 7 microKelvin


RF 570kHz

BEC! A condensate forms below the critical temperature of 250 nK.  The diameter of the condensate is about 2 micrometers which is well below the resolution of our imaging system.



Raw image data

The condensate is better viewed after 10ms of ballistic expansion.  These three images are of atom clouds just above, just below and well below the critical temperature. These are the raw date for the 3D false colour images above.

Earlier results

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BEC & QO Group | Department of Physics | University of Queensland
Last updated: Tuesday 24th February 2004