On May 27, 2003, our team at the
Institute for Experimental Physics at
University achieved Bose-Einstein condensation (BEC) of rubidium
87 in the ground state F=2, mF = 2.
The two pictures are false color and greyscale images of clouds of rubidium atoms at condensation. The narrow peak of the condensate grows out of the broad thermal atom cloud at the critical temperature Tc. These images are taken after 15 ms of time of flight. The pictures are taken along the long axis (z- axis) of our cigar shaped condensate.
Three condensate wavepackets appear instead of a single one because some atoms flip their spin when we turn off the magnetic trap fields. This is due to eddy currents in the metal mount of the magnetic quadrupole coils which produce uncontrolled magnetic fields when the magnetic coils are switched off. The resulting various spin components (here mF = 2, 1, 0) are separated by a magnetic field gradient (Stern-Gerlach effect).
The sickel shaped deformation of the wavepackets is due to the mean field interaction between the atoms.
Trap/ condensate parameters:
Our BEC machine features the magnetic transport concept developed in Munich [Gre00] and is designed for maximum access and flexibility to host demanding experiments. Our apparative concept is particularly advantageous for experiments using 3D optical lattices and high resolution imaging.
The Rb atoms are first collected into a magneto-optical trap (MOT)
in a compact stainless-steel cell and then loaded into a magnetic
quadrupole trap. The quadrupole potential is then moved over a
distance of about 49 cm into an extreme UHV (10-11 mBar)
glass cell using a chain of quadrupole coils. By running suitable
currents through the quadrupole coil pairs the trapping geometry of
the potential is maintained during the transport process, thus
minimizing heating of the trapped atom cloud. The whole apparatus is
designed to be very flat (5 cm) so that the transport coils can be
run with moderate currents (~100 A). Once in the glass cell, the trap
is changed to Ioffe-Pritchard (or TOP) configuration and the atoms
are Bose condensed following standard evaporation methods.
BEC research worldwide
Bose-Einstein condensation in ultracold atomic gases was first realized in 1995 with 87Rb, 23Na, and 7Li. This pioneering work was honored with the Nobel prize 2001 in physics , awarded to Eric Cornell, Carl Wieman, and Wolfgang Ketterle. Since then, the research field has exploded with many groups working on BEC worldwide . Only a few more species could be condensed so far: Hydrogen (1998), 85Rb (2000), metastable 4He (2001), and 41K (2001). There have been several attempts to condense cesium, the Innsbruck experiment is the first one to reach this goal.
We are supported by the Austrian Science Fund (Fonds zur Förderung der wissenschaftlichen Forschung, FWF) in the frame of the Spezialforschungsbereich F15 "Control and Measurement of Coherent Quantum Systems".
last change: 05-12-15 by JH