Dynamics of a Bose-Einstein condensate at finite temperature in an atom-optical coherence filter

The macroscopic coherent tunneling through the barriers of a periodic potential is used as an atom-optical filter to separate the center of mass of the condensate and the thermal components of a 8 7 Rb mixed cloud. We condense in the combined potential of a laser standing wave superimposed on the axis of a cigar-shaped magnetic trap and induce condensate dipole oscillation in the presence of a static thermal component. The oscillation is damped due to the interaction with the thermal fraction and we investigate the role played by the periodic potential in the damping process.