  We report on the confinement of a Bose-Einstein condensate in an annular trap
with widely tunable parameters. The trap relies on a combination of magnetic,
optical and radio-frequency fields. The loading procedure is discussed. We
present annular traps with radii adjusted between 20 and 150 micrometers. We
demonstrate the preparation of persistent flows both with a rotating laser
stirrer and with a global quadrupole deformation of the ring.Our setup is well
adapted for the study of superfluid dynamics.
