Influence of inter-strand electrical and thermal conductivity on stability of Rutherford cables in accelerator magnets

Influence of inter-strand electrical and thermal conductivity on stability of multi-strand superconducting cables is studied theoretically based on a 3-strand cable model. The simulation model takes into account transient heat-transfer characteristics between strand surface and helium, inter-strand current sharing, heat conduction as well as variation of thermal physical properties with temperature and magnetic field. Minimum quench energy is calculated both in case of uniform current distribution and in the case of nonuniform current distribution. The results show that the influence of inter-strand electrical conductivity on minimum quench energy increases as the nonuniformity of current distribution increases. Calculations were performed in view of the special situation of Rutherford cables in dipole magnets for particle accelerators. The results demonstrated that differences in inter-strand contact properties could lead to evident different ramp-rate limitation behavior. It is concluded that serious ramp-rate limitation problem could be avoided by keeping inter-strand electrical and thermal conductivity in a proper range.