A cloud of 10^10 laser-cooled rubidium atoms in a magneto-optical trap (MOT) loaded by a Zeeman slower. This experiment was performed in the cold atom group at Paul Sabatier University, Toulouse, France (LCAR, UMR 5589 of CNRS).
The atoms (that scatter light and appear white on the images) are trapped in a ultra-high vacuum chamber by means of magnetic fields and six laser beams. If one switches off the magnetic field (00:24) one creates “optical molasses”: the atoms are not trapped, but simply cooled in a “viscous” medium made by light.
We can move the cloud by adding an extra magnetic field (00:30 to 00:45). When turning off the source (Zeeman slower), the MOT decays due to background gas collisions (00:45 to 0:54). We then block one trapping laser, which destroys the trapped cloud. When unblocking the beam, new atoms are quickly loaded into the MOT (end of the video).
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