AC losses of internally deposited Nb3Ge films

Nb3Ge films deposited on the inside of a copper tube have been measured. The tubular sample was modified into a tape sample for measuring purposes. The total ac losses contain the substrate loss as well as the superconductor loss, and by varying the frequency and the field the two are separated. The plot of the loss vs. the surface roughness indicates that the losses in this case are dominated by the superconducting diffusion layer. The problem presented by the diffusion layer in any partially coated tape is stressed.