Skip to Content

It's freezing in Paris-Nord

[Historical report created from GSU BEC Homepage:]

"BEC was observed in 87Rb, |F, MF> = |2, 2> by the LPL (Laboratoire de Physique des Lasers) group at the Universitй Paris-13 on January 12, 2001.

Our main objective is to compress the BEC cloud into a two-colour evanescent dipole trap in order to reach the quasi 2D quantum gas regime. Our experimental set-up is based on the double MOT scheme: the Ioffe-Pritchard magnetic trap is similar to the QUIC (Quadrupole and Ioffe Configuration) as first demonstrated in the Hänsch group by T. Esslinger and I. Bloch. At the present time, the number of atoms in the condensate is about 105. The absorption images taken at different times of flight clearly show the change of anisotropy.

The experimental details are as follows:

  • The 2 MOTs are 70 cm apart. The second MOT consists of two pair of beams in the horizontal plane and one pair vertical going trough a dielectric slab waveguide. The slab waveguide is to produce evanescent waves and its distance from the QUIC trap is adjustable.
  • Loading: a pushing beam, 120 MHz red detuned from the F = 2 - F = 3 transition is focalized in the first upper MOT. 109 atoms are loaded in the second MOT within 30 seconds.
  • Magnetic trapping: after 5 ms of MOT compression, 10 ms of gradient cooling, optical pumping to the |2, 2> state with respect to the Ioffe coil axis, one third of the initial population is transferred in a quadrupole trap. The quadrupole is adiabatically transferred into the QUIC trap within 2 seconds.
  • QUIC trap characteristics: the magnetic field gradient is 225 G/cm and the curvature is 270 G/cm2 with electrical power less than 150 watts. Axial and radial frequencies are 21 Hz and 300 Hz. The lifetime in the trap is over 90 s.
  • RF evaporation is performed in 45 s with an exponential ramp from 20 MHz down to 1.535 MHz. The RF knife at 1.55 MHz corresponds to the phase transition at 500 nK.

The BEC team members are

  • Yves Colombe
  • Hélène Perrin
  • Brigitte Mercier
  • Vincent Lorent

Michel Gorlicki, Jean-Claude Keller and Martial Ducloy have contributed at various stages of the project.

The laboratory staff who contributed to the experimental work

  • Olivier Lopez and Jean-Yves Chauvet for the electronics
  • Michel Fosse and Gérard Baquè for the specials in machining
  • Thierry Billeton for the specials in optics

For more information visit our web site

or email

Vincent Lorent "