Problems with the external diffusion process for producing Nb3Sn-Cu superconducting wire

Abstract
It has been observed that in the external diffusion process for producing Nb3Sn‐Cu superconducting wire, dewetting of the Sn layer occurs for layer thicknesses on the order of 6 μm and larger. A mechanism for this dewetting is proposed and it is demonstrated that the problem may be eliminated by formation of an oxide skin on the outer surface of the Sn layer.