Time Dependence of Persistent Current Effects in the Superconducting HERA Magnets

The higher multipole fields which are generated by persistent eddy currents in the HERA dipole and quadrupole magnets show a logarithmic time dependence for times between 200 s and 4000 s. The persistent current contribution to the main field of the magnets decreases as well. The logarithmic decay rates vary considerably from magnet to magnet and are quite different for superconductors from different manufacturers. Theinfluence of various parameters is investigated.