Axel Griesmaier (Tilman Pfau - group)
A continuous source of ultracold atoms
We have realized a continuous scheme to load ultracold chromium atoms into a magnetic guide. Such a continuous source is one prerequisite for a cw atom laser and has potential as a source for atom lithography using ultracold atoms. We produce a high flux beam of 5x109 ultracold atoms at temperatures on the order of a few tens of microkelvin in radial and a few hundred microkelvin in longitudinal direction and with a directed mean velocity of around 5 m/s. Recently we have demonstrated additional Doppler cooling in the guide which increases the phase space density of the beam by more than an order of magnitude. We propose a scheme based on optical pumping between trapped and anti-trapped Zeeman states that dissipates the directed kinetic energy. At the same time this scheme acts as a "diode" for atoms which allows to load them from the guide into a deep optical trapping potential. We discuss the loading mechanism and its expected efficiency.
