Disclosed herein are superconducting wires. The superconducting wires can comprise a metallic matrix and at least one continuous subelement embedded in the matrix. Each subelement can comprise a non-superconducting core, a superconducting layer coaxially disposed around the non-superconducting core, and a barrier layer coaxially disposed around the super-conducting layer. The superconducting layer can comprise a plurality of Nb.sub.3Sn grains stabilized by metal oxide particulates disposed therein. The Nb.sub.3Sn grains can have an average grain size of from 5 nm to 90 nm (for example, from 15 nm to 30 nm). The superconducting wire can have a high-field critical current density (J.sub.c) of at least 5,000 A/mm.sup.2 at a temperature of 4.2 K in a magnetic field of 12 T. Also described are superconducting 4 wire precursors that can be heat treated to prepare super-conducting wires, as well as methods of making super-conducting wires.

A compound superconducting twisted wire includes compound superconducting strands being twisted to form a twisted structure, in which each of the compound superconducting strands includes a compound superconductor part, a reinforcing part and a stabilizing part. The compound superconductor part includes compound superconducting filaments and a first matrix, the compound superconducting filaments each including a compound superconducting phase. The reinforcing part is disposed on an outer circumferential side of the compound superconductor part and includes reinforcing filaments and a second matrix. The stabilizing part is disposed on at least one side of an inner circumferential side and an outer circumferential side of the reinforcing part. A volume ratio of the reinforcing part relative to the compound superconducting strand is larger than a volume ratio of the compound superconductor part relative to the compound superconducting strand.

This compound superconducting precursor wire includes: a compound superconducting precursor portion including a plurality of compound superconducting precursor filaments, and a first matrix precursor having the plurality of compound superconducting precursor filaments embedded therein and including a first stabilizing material; a reinforcing material portion disposed on an outer peripheral side of the compound superconducting precursor portion; and a stabilizing material portion which is disposed on at least one of an inner peripheral side and an outer peripheral side of the reinforcing material portion, and consisting of a second stabilizing material, in which a Vickers hardness (HV) of the stabilizing material portion is 90 or less, and a 0.2% tensile strength of the compound superconducting precursor wire is 200 MPa or more.

In a method for coating a base body, a first target and a second target are arranged in a vacuum chamber. A base body to be coated is arranged in the vacuum chamber is heated to a coating temperature of less than 600 C. During sputtering with sputter gas ions, first target particles are liberated from the first target and second target particles are liberated from the second target and are deposited as coating particles on the base body. A first sputter rate is specified for the first target and a second sputter rate is specified for the second target such that, during the sputtering process, the coating is generated as an A15 phase with an intended stoichiometric ratio of the first target particles to the second target particles. A functional element has a base body and a coating of Nb.sub.3Sn applied directly on the surface of the base body.

In various embodiments, superconducting wires incorporate diffusion barriers composed of Nb alloys or NbTa alloys that resist internal diffusion and provide superior mechanical strength to the wires.

A system and method for treating a cavity comprises arranging a niobium structure in a coating chamber, the coating chamber being arranged inside a furnace, coating the niobium structure with tin thereby forming an Nb.sub.3Sn layer on the niobium structure, and doping the Nb.sub.3Sn layer with nitrogen, thereby forming a nitrogen doped Nb.sub.3Sn layer on the niobium structure.

In various embodiments, superconducting wires incorporate diffusion barriers composed of Nb alloys or NbTa alloys that resist internal diffusion and provide superior mechanical strength to the wires.

A system and method for treating a cavity comprises arranging a niobium structure in a coating chamber, the coating chamber being arranged inside a furnace, coating the niobium structure with tin thereby forming an Nb.sub.3Sn layer on the niobium structure, and doping the Nb.sub.3Sn layer with nitrogen, thereby forming a nitrogen doped Nb.sub.3Sn layer on the niobium structure.