A Smooth, Inductively Coupled Ring Trap for Atoms
  We propose and numerically investigate a scalable ring trap for cold atoms that surmounts problems of roughness of the potential and end--effects of trap wires. A stable trapping potential is formed about an electrically isolated, conducting loop in an ac magnetic field by time averaging the superposition of the external and induced magnetic fields. We investigate the use of additional fields to eliminate Majorana spin flip losses and to create novel trapping geometries. The possibility of micro--fabrication of these ring traps offers the prospect of developing Sagnac atom interferometry in atom--chip devices. 
P. F. Griffin, E. Riis, and A. S. Arnold