Escape of a Josephson vortex trapped in an annular Josephson junction

Experiments on the thermal escape of a Josephson vortex trapped in a magnet ic field-induced potential are reported. The measured critical current stat istics in a wide range of applied magnetic field H shows that the vortex es cape temperature T-e similar or equal to T at large magnetic fields and T-e >> T for small values of H. We have developed a theory of vortex escape wh ich explains the increase of T-e by the presence of a small residual pinnin g in the junction. A peculiar regime when vortex changes its shape in the p rocess of escape is also analyzed. (C) 2000 Elsevier Science B.V. All right s reserved.