A. Metals C. Critical current density C. Critical field

density available in long length accelerator quality strand has almost doubled. The microstructural and that a reliable conductor-magnet technology can be developed. Two A15 superconductors, Nb3Sn and Nb3Al, are available in con-ductor form and push the available field well beyond 12 T. The development of high performance Nb3Al strand is reviewed else-where in this publication [1]. Nb3Sn technology has also been the subject of a recent historical review by Suenaga [2] and aspects that could clearly work in the field and temperature domain not accessible to Nb–Ti [5] and to show that non-stabilizer critical cur-rent density (Jc) values beyond 2000 A/mm2 at 12 T (4.2 K) could be reached [6]. The PIT technique is extensively reviewed by Godeke elsewhere in this journal [7], while here we concentrate mainly on characterizations that we have made of the Internal Sn (IT) Pro-cess wires. Earlier work of ours in the 1999–2004 time frame on the PIT wires led us to important conclusions about the way that radial inhomogeneities produced by the Sn diffusion step needed to form the Nb3Sn affect the properties of wires. These inhomoge-neities are present in all filamentary conductor designs [8], but to