WG 6 - TC 90/WG 6

IEC 61788-27:2025 specifies a test method for the twist pitch measurement of Nb‑Ti/Cu and Nb‑Sn/Cu composite superconductors by an untwisting method.
The test method is applicable to Nb‑Ti/Cu and Nb‑Sn/Cu composite superconducting wires with monolithic structures, which have either a round cross section with a diameter ranging from 0,2 mm to 2 mm or a rectangular cross section that is equivalent in area to the round cross‑sectional wires. These wires possess a filament diameter ranging from 6 µm to 200 µm, a twist pitch between 5 mm and 50 mm, and a matrix of copper or copper alloy. This document uses nitric acid to remove the matrix (copper or copper alloy), so the surface of the composite superconducting wire can be plated with a material that is dissolvable by nitric acid.
Though uncertainty can increase, the method can apply to Nb‑Ti/Cu or Nb‑Sn/Cu composite superconducting wires when the parameters of cross-sectional area, filament diameter and twist pitch are out of the limit.
The test method specified in this document is expected to apply to other types of composite superconducting wires after some appropriate modifications.

IEC 61788-12:2013 describes a test method for determining the copper to non-copper volume ratio of Cu/Nb3Sn wires. The test method given hereunder is applicable to Nb3Sn composite superconducting wires with a cross-sectional area of 0,1 mm2 to 3,0 mm2 and a copper to non-copper volume ratio of 0,1 or more. It does not make any reference to the filament diameter; however, it is not applicable to those superconducting wires with their filament, Sn, Cu-Sn alloy, barrier material and other non-copper portions dispersed in the copper matrix or those with the stabilizer dispersed. Furthermore, the copper to non-copper volume ratio can be determined on specimens before or after the Nb3Sn formation heat treatment process. The Cu/Nb3Sn wire has a monolithic structure with a round or rectangular cross-section. Though uncertainty increases, this method may be applicable to the measurement of the copper to non-copper volume ratio of the Cu/Nb3Sn wires whose cross-section and copper to non-copper volume ratio fall outside the specified ranges. This test method may be applied to other composite superconducting wires after some appropriate modifications. This second edition cancels and replaces the first edition published in 2002. It constitutes a technical revision. The main revision is the addition of two new annexes, "Uncertainty considerations" and "Uncertainty evaluation in the test method of the copper to non-copper volume ratio of Nb3Sn composite superconducting wires".

IEC 61788-5:2013 covers a test method for the determination of copper to superconductor volume ratio of Cu/Nb-Ti composite superconducting wires. This test method and the alternate method in Annex are intended for use with Cu/Nb-Ti composite superconducting wires with a cross-sectional area of 0,1 mm2 to 3 mm2, a diameter of the Nb-Ti filament(s) of 2 micrometers to 200 micrometers, and a copper to superconductor volume ratio of 0,5 or more. The Cu/Nb-Ti composite test conductor discussed in this method has a monolithic structure with a round or rectangular cross-section. This test method is carried out by dissolving the copper with nitric acid. Deviations from this test method that are allowed for routine tests and other specific restrictions are given in this standard. Cu/Nb-Ti composite superconducting wires beyond the limits in the cross-sectional area, the filament diameter and the copper to superconductor volume ratio could be measured with this present method with an anticipated reduction of uncertainty. Other, more specialized, specimen test geometries may be more appropriate for conductors beyond the limits and have been omitted from this present standard for simplicity and to retain low uncertainty. The test method given in this standard is expected to apply to other superconducting composite wires after some appropriate modifications. The copper to superconductor volume ratio of composite superconductors is used mainly to calculate the critical current density of superconducting wires. The test with the method given in this International Standard may be used to provide part of the information needed to determine the suitability of a specific superconductor. Moreover, this method is useful for quality control, acceptance or research testing if the precautions given in this standard are observed. This second edition cancels and replaces the first edition published in 2000. It constitutes a technical revision. The main revisions are the addition of two new annexes, "Uncertainty considerations" (Annex E) and "Uncertainty evaluation in test method of copper to superconductor volume ratio of Cu/Nb-Ti composite superconductors" (Annex F).

Describes the test method for determining the copper to non-copper volume ratio of Cu/Nb3Sn wires. The test method given hereunder is applicable to Nb3Sn composite superconducting wires with a cross-sectional area of 0,1 mm2 to 3 mm2 and a copper to non-copper volume ratio of 0,1 or more. It does not make any reference to the filament diameter; however, it is not applicable to those superconducting wires with their filament, Sn, CuSn, barrier material and other non-copper portions dispersed in the copper matrix or those with the stabilizer dispersed. Furthermore, the copper to non-copper volume ratio can be determined on specimens before or after the Nb3Sn formation heat treatment process. This test method may be applied to other composite superconducting wires after some appropriate modifications.

Covers a test method for the determination of copper to superconductor volume ratio of Cu/Nb-Ti composite superconducting wire. The Cu/Nb-Ti composite test conductor discussed in this method has a monolithic structure with a round or rectangular cross-section. This test method is carried out by dissolving the copper with nitric acid. Deviations from this test method that are allowed for routine tests and other specific restrictions are given in this standard.