Conventional doping methods that directly add C or a C-bearing species to Mg+B powder have the disadvantage of adding C inhomogeneously, yielding either under-reacted regions or blocking phases. Pre-doped B powder provides a more homogeneous distribution of the C dopant in MgB 2 . Powders containing varying amounts of C were used to produce in-situ MgB 2 strands which showed high values of transport J c (10 4 A/cm 2 at 13.3T). Compared to SiC-added and malic acid-treated strands the pre-doped MgB 2 showed both higher values of B irr and transport J c , indicating that the pre-doping of B leads to more efficient C substitution into the B-sublattice.

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