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First observation: BEC!

Group: Boshier

Authors and contributors: Aidan Arnold, Calum MacCormick and Malcolm Boshier

[Historical report created from GSU BEC Homepage:]

"BEC was observed in Britain at the University of Sussex on 22nd September. Details of the experiment are as follows:

  • Cold Rb atoms are collected for about 1 minute in a double MOT. The experiment uses two moderate power (50 mW) diode lasers, one providing repump light and the other supplying both sets of trapping beams as well as the pump and probe light.
  • About 3 x 108 atoms are transferred from the MOT to a "baseball" Ioffe-Pritchard trap where they are compressed adiabatically to increase the elastic collision rate (final trap frequencies are 11 and 250 Hz). The atoms are then evaporatively cooled down to the BEC transition temperature.
  • Following their release from the trap, the atoms are allowed to expand ballistically for several ms before detection by absorption imaging with a standard video camera.

We were pleasantly surprised that our first observation of runaway evaporation lead directly to BEC. We have repeatedly observed the BEC signature of a dense narrow spike forming in the center of the cold atom cloud as the atoms are cooled through the BEC transition temperature. Our first condensates are smaller (~2 x 104) than expected for the initial load of the magnetic trap, indicating that there is still considerable room for optimization. Recent results, including images of the condensate, and further details of the experiment can be found on our web page[obsolete].

The Sussex BEC group is Aidan Arnold, Calum MacCormick and Malcolm Boshier."

Posted: 11 Aug 2005     Date: 22 Sep 1998

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