Escape of a Josephson vortex trapped in an annular Josephson junction

Experiments on the thermal escape of a Josephson vortex trapped in a magnetic field-induced potential are reported. The measured critical current statistics in a wide range of applied magnetic field H shows that the vortex escape temperature Te?T at large magnetic fields and Te?T for small values of H. We have developed a theory of vortex escape which explains the increase of Te by the presence of a small residual pinning in the junction. A peculiar regime when vortex changes its shape in the process of escape is also analyzed.