material which is also an adequate thermal conductor for uniform cooling of the composite conductor also most applications of the composite conductor require that the composite conductor be formed into a cable or wire the barrier 32 must be formed from a material which will maintain its properties after high temperature processing of the composite hyperconductor through extrusion rolling or other cross sectional area reduction processes conventional aluminum alloy matrices are relatively easy to process into wire however if the high purity aluminum hyperconductor is in contact with a conventional aluminum alloy matrix at the elevated temperatures required for cross sectional area reduction of the composite into a cable or wire migration of elements from the alloy into the high purity core would contaminate the high purity core increasing the residual resistivity of the core while the use of dispersion strengthened aluminum alloys as the matrix would reduce the amount of contamination during processing the ideal material for barrier 32 would also function as a diffusion barrier to prevent contamination of the high purity aluminum core while permitting use of conventional aluminum alloys as the matrix material fig4 depicts a preferred embodiment of a multifilamentary lightweight cryogenic conductor 34 consisting of filaments 36 of a hyperconducting material preferably high purity aluminum a matrix 38 provides strength for the composite to compensate for the low mechanical strength of the high purity aluminum filaments a barrier 40 surrounds each of.