Magnetic field stability of superconducting magnets

A simple qualitative model is proposed to explain the fast initial change of the magnetic field of superconducting magnets which operate in the persistent mode. Using this model the additional component of the transport current which is induced by the decaying screening currents can be represented. The analytical results are in good qualitive agreement with the experimental curves. By a suitable cyclic approach to the frozen-in current it is possible to attain very good stability from the start.