Strain dependence of critical current in advanced Nb3Sn superconductors

Parameters relevant to the strain dependence of critical current Ic have been investigated with emphasis on the correlation with the conductor constitution and heat treatment. Examinations have been made on several advanced Nb3Sn conductors which are in the course of development. The conductors involved are: bronze processed Nb3Sn conductors with third element, internally stabilized conductors, internally reinforced conductors, internal tin diffusion processed conductors and in situ processed conductors. The strain characteristics are specified in terms of precompression strain, reversible limit strain and strain sensitivity of Ic. Improvement of the strain characteristics in these conductors through proper choice of parameters is briefly discussed. Effect of neutron irradiation on the strain dependence of the conductors is also presented. Changes in the mechanical properties of the constituents induced by irradiation alter the strain characteristics of Ic. Role of the third additive element to the irradiation-strain synergistic effect is discussed with emphasis on both the amount and the species of the additive element. (author). 18 refs, 9 figs