Quasi-Adiabatic External State Preparation of Ultracold Atoms in Microgravity

The Cold Atom Laboratory on the International Space Station produces ultracold gases of rubidium and potassium in a tight magnetic trap near the surface of a magnetic chip. In order to use these samples in long-duration field-free experiments, the atoms must be moved away from the chip, expanded to larger volume, and released from the trap. We describe how these goals can be achieved using quasi-adiabatic techniques. For rubidium atoms, we demonstrate a displacement of 0.6 mm and expansion into a trap with a mean oscillation frequency of 6.4 Hz. The center-of-mass release velocity and the condensate expansion velocity are about 0.2 mm/s each. An unexpectedly large background magnetic field gradient is observed, which limits the usable interaction time for the released atoms.