Time-averaged adiabatic ring potential for ultracold atoms

We report the experimental realization of a versatile ring trap for ultracold atoms. The ring geometry is created by the time-averaged adiabatic potential resulting from the application of an oscillating magnetic bias field to a rf-dressedquadrupole trap. Lifetimes for a Bose-Einstein condensate in the ring exceed 11s and the ring radius was continuously varied from 50 mu m to 262 mu m. An efficient method of loading the ring from a conventional time-averaged orbiting potentialtrap is presented together with a rotation scheme which introduces angular momentum into the system. The ring presents an opportunity to study the superfluid properties of a condensate in a multiply connected geometry and also has applications for matter-wave interferometry.