Atom Chips in the real World: The role of wire corrugation

Thorsten Schumm

Institut d'Optique, CNRS, Centre Scientific, Bat. 503, 91403 Orsay, France

Atom chips have proven to be a powerfull tool in atom optics. They combine robusteness, simplicity and low power consumption with strong confinement and high flexibility in the design of the trapping geometry. "Real world" limitations of this system are therefore of special interest: losses and heating of atoms close to room temperature metallic surfaces have been theoretically predicted and experimentally observed soon after the first realization of atom chips. An unpredicted phenomenon was the fragmentation of trapped cold atomic clouds or Bose condensates in magnetic microtraps. It has been shown, that this fragmentation is due to static distortions of the curent flow inside the wires, creating a coresponding roughness in the trapping potential. In our work, we present a quantitative analysis of the potential roughness created by micro wires. The trapping potential of a chip trap was probed using cold atoms. We analized the trapping wire and its geometrical edge and surface defects using SEM and AFM techniques. A theoretical model allows us to calculate the potential, that one can expect from such a wire. We find good aggreement between the potential rougness measured with atoms and the one calculated from the wire shape, explaining the fragmentation observed in our experimantal system by geometrical wire deformations. We will present rougness measurements for wires produced by different techniques of microfabrication.