On August 11th, 2004 we made the first sodium BEC in our setup.
The temperature of the BEC was approximately 200nK, and about 106 atoms were trapped.
Starting from a MOT of 3 billion Na atoms at 400 microK we have on the left after evaporative cooling a thermal cloud of 50 million Na atoms at a temperature of 2 microK. After further cooling we obtain a condensate surrounded by a thermal cloud of 30 million atoms at a temperature of 800 nK (middle). On the right we have a almost pure condensate of 8 million atoms at a temperature of 100 nK.
The set-up for the study of optical lattices is currently under construction. To observe collective effects of atoms in an optical lattice a high density of the atoms is necessary and we are improving the cooling and trapping of the atoms towards this end. Atoms are slowed in the Zeeman slower and compressed in a magneto-optical compressor to a small beam diameter. This beam is deflected by a few degrees and thus separated from the "hot" beam. The "cold" beam is used to load a magneto-optical trap. To increase the density of the atoms in the trap we are exploiting the principle of a so-called "dark" magneto-optical trap. To create the optical lattice we have installed a new laser system with a Coherent Verdi 5W solid-state laser pumping a Coherent 699 dye laser, so the frequency of the lattice becomes tunable. This way we have sufficient intensity to create a deep optical lattice potential.