Bidirectional propagation of cold atoms in a "stadium" shaped magnetic   guide
  We demonstrate the bi-directional propagation of more than 10 7 atoms (87 Rb) around a "stadium" shaped magnetic ring that encloses an area of 10.9 cm 2, with a flux density exceeding 10 11 atoms sec -1 cm -2 . Atoms are loaded into the guide from a 2D + MOT at one side of the "stadium". An optical standing wave pulse is applied to increase the propagation velocity of atoms along the waveguide. The atom sample fills the entire ring in 200 ms when counterpropagating atom sections of the original atom cloud recombine at their initial positions after a full revolution. We discuss a possible extension of this result to a guided atom ring interferometer. 
Saijun Wu, Wilbert Rooijakkers, Pierre Striehl, Mara Prentiss