a thin film superconductor assembly is disclosed along with a method of fabricating same . the assembly comprises a self - supporting substrate defining at least a portion of a containment for a flow of cryogenic fluid , a dielectric layer adherent to a surface of the substrate , a thin film superconductor adherent to the dielectric layer and a moisture and oxygen impervious electrically insulating coating covering the thin film superconductor . a method of forming such thin film superconductor assembly , wherein the dielectric layer consists essentially of aluminum nitride , comprises growing the aluminum nitride dielectric layer integrally on the surface of the substrate .