Bidirectional propagation of cold atoms in a “stadium”-shaped magnetic guide

We demonstrate the bidirectional propagation of more than 10⁷0.3em0exatoms (⁸⁷Rb) around a ``stadium''-shaped magnetic ring that encloses an area of 10.90.3em0excm², with a flux density exceeding 10¹¹0.3em0exatom0.2em0exs^-10.2em0excm^-2. Atoms are loaded into the guide from a two-dimensional (and higher) magneto-optical trap 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 2000.3em0exms when counterpropagating atom sections of the original atom cloud recombine at their initial positions after a full revolution.