Dynamic stability and quenching currents of superconducting multifilamentary composites under usual cooling conditions

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Abstract
Although the filaments in a composite are individually stable against the flux jump, the self-field of the conductor as a whole gives rise to stability problems. The way in which flux penetrates into the composite is determined by the apparent thermal and magnetic diffusivities. If the ratio of these two diffusivities is not small, the flux jumps can be slowed down. Therefore, it is too pessimistic to consider only adiabatic conditions in composites as usual. The differential thermal and electrical equations have been solved in the case of a cylindrical composite, taking into account the particular conditions of cooling. Stability of the composite is only achieved if a criterion more optimistic and realistic than the well-known adiabatic criterion is satisfied. Stability curves may be used to predict the degraded quenching currents of a composite in the presence of the flux jump if the thermal diffusivity and the enthalpy of the medium in contact with the conductor are included.