Degradation of the Cu Residual Resistivity Ratio in Cr-Plated Composite Nb&lt;sub&gt;3&lt;/sub&gt;Sn Wires

Alknes, P.; Bordini, B.; Bártová, Barbora; Izquierdo, G. Arnau; Cantoni, Marco; Devred, A.; Vostner, A.; Ballarino, A.; Bottura, L.

doi:10.1109/tasc.2015.2402174

Cited by 3 publications

(8 citation statements)

References 18 publications

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“…It is evident that the diffusion coefficients obtained in this work is significantly higher than those in [31] and [32]. If we considered the possible precipitation of Cr during cooling from heat treatment temperature, as suggested by Alknes et al [23], to cause the measured low RRR, the diffusion coefficient would have been even higher. This discrepancy was also observed by Novosilova et al [22] who suggested that diffusion of other elements that co-exist in the Cr coating, such as oxygen, might be the cause.…”

Section: Rrr Experimental Results and Calculationcontrasting

confidence: 42%

“…This discrepancy was also observed by Novosilova et al [22] who suggested that diffusion of other elements that co-exist in the Cr coating, such as oxygen, might be the cause. However, as Alknes et al [23] pointed out, oxygen as a main cause of RRR degradation is not likely. This is because the diffusion coefficient of O in Cu (also listed in table 3) is about six orders of magnitude greater than that of Cr in Cu.…”

Section: Rrr Experimental Results and Calculationmentioning

confidence: 98%

“…It is known that RRR of Cr plated strands decreases with increasing heat treatment time [19][20][21][22][23]. In order to verify that Cr layer is the main contributor to RRR degradation, the Cr layer is removed from a set of x from Cr/Cu interface and at time t can be calculated by a complementary error function [19],…”

Section: Rrr Experimental Results and Calculationmentioning

confidence: 99%

“…This is a very challenging measurement, due to extremely high detection sensitivity needed. Previous measurements by laser mass spectrometer [20], and high sensitivity EDS [23] only had limited success.…”

Section: Rrr Experimental Results and Calculationmentioning

confidence: 99%

“…Moreover, it has been reported that Residual Resistance Ratio (RRR) of Cr plated ITER strands decrease with increasing heat treatment time [19][20][21][22][23]. This has been attributed to Cr diffusion into copper stabilizer.…”

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confidence: 99%

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Influence of heat treatment excursion on critical current and residual resistivity ratio of ITER Nb₃Sn strands

Lü¹,

McGuire²,

Hill³

et al. 2017

Supercond. Sci. Technol.

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Heat treatment is critically important to the performance of Nb3Sn superconducting strands. For very large Nb3Sn magnet coils, such as the International Thermonuclear Experimental Reactor (ITER) Central Solenoid (CS) coils, heat treatment carries risk of temperature and time excursion, which may result in performance degradation. Therefore, it is prudent to study the effect of possible excursion on Nb3Sn performance. In this study, Nb3Sn strands used for ITER CS coils are heat treated at different temperatures for different times. Their critical current, residual resistance ratio and hysteresis losses are measured. It is found that in the range we studied, critical current and hysteresis losses do not change significantly. Residual resistance ratio, however, decreases with increasing heat treatment temperature and time. This is attributed to the diffusion of metallic elements from the plated Cr layer to the copper stabilizer. Based on a model of metallic elements diffusion, a numerical code is developed to predict residual resistance ratio as a function of heat treatment temperature and time.

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Section: Rrr Experimental Results and Calculationcontrasting

confidence: 42%

Section: Rrr Experimental Results and Calculationmentioning

confidence: 98%

Section: Rrr Experimental Results and Calculationmentioning

confidence: 99%

Section: Rrr Experimental Results and Calculationmentioning

confidence: 99%

mentioning

confidence: 99%

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Influence of heat treatment excursion on critical current and residual resistivity ratio of ITER Nb₃Sn strands

Lü¹,

McGuire²,

Hill³

et al. 2017

Supercond. Sci. Technol.

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Statistical analysis of the Nb₃Sn strand production for the ITER toroidal field coils

Vostner¹,

Jewell

Pong

et al. 2017

Supercond. Sci. Technol.

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The ITER toroidal field (TF) strand procurement initiated the largest Nb 3 Sn superconducting strand production hitherto. The industrial-scale production started in Japan in 2008 and finished in summer 2015. Six ITER partners (so-called Domestic Agencies, or DAs) are in charge of the procurement and involved eight different strand suppliers all over the world, of which four are using the bronze route (BR) process and four the internal-tin (IT) process. In total more than 500 tons have been produced including excess material covering losses during the conductor manufacturing process, in particular the cabling. The procurement is based on a functional specification where the main strand requirements like critical current, hysteresis losses, Cu ratio and residual resistance ratio are specified but not the strand production process or layout. This paper presents the analysis on the data acquired during the quality control (QC) process that was carried out to ensure the same conductor performance requirements are met by the different strand suppliers regardless of strand design. The strand QC is based on 100% billet testing and on applying statistical process control (SPC) limits. Throughout the production, samples adjacent to the strand pieces tested by the suppliers are cross-checked ('verified') by their respective DAs reference labs. The level of verification was lowered from 100% at the beginning of the procurement progressively to approximately 25% during the final phase of production. Based on the complete dataset of the TF strand production, an analysis of the SPC limits of the critical strand parameters is made and the related process capability indices are calculated. In view of the large-scale production and costs, key manufacturing parameters such as billet yield, number of breakages and piece-length distribution are also discussed. The results are compared among all the strand suppliers, focusing on the difference between BR and IT processes. Following the completion of the largest Nb 3 Sn strand production, our experience gained from monitoring the execution of the QC activities and from auditing the results from the measurements is summarised for future superconducting strand material procurement activities.

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The Effect of Diffusion Annealing of Nb3Sn-Based Superconductors with Internal Tin Sources on the Conductivity of Stabilizing Copper

Novosilova

Polikarpova

Abdyukhanov

et al. 2021

Phys. Metals Metallogr.

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Degradation of the Cu Residual Resistivity Ratio in Cr-Plated Composite Nb<sub>3</sub>Sn Wires

Cited by 3 publications

References 18 publications

Influence of heat treatment excursion on critical current and residual resistivity ratio of ITER Nb₃Sn strands

Influence of heat treatment excursion on critical current and residual resistivity ratio of ITER Nb₃Sn strands

Statistical analysis of the Nb₃Sn strand production for the ITER toroidal field coils

The Effect of Diffusion Annealing of Nb3Sn-Based Superconductors with Internal Tin Sources on the Conductivity of Stabilizing Copper

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Degradation of the Cu Residual Resistivity Ratio in Cr-Plated Composite Nb<sub>3</sub>Sn Wires

Cited by 3 publications

References 18 publications

Influence of heat treatment excursion on critical current and residual resistivity ratio of ITER Nb3Sn strands

Influence of heat treatment excursion on critical current and residual resistivity ratio of ITER Nb3Sn strands

Statistical analysis of the Nb3Sn strand production for the ITER toroidal field coils

The Effect of Diffusion Annealing of Nb3Sn-Based Superconductors with Internal Tin Sources on the Conductivity of Stabilizing Copper

Contact Info

Product

Resources

About

Influence of heat treatment excursion on critical current and residual resistivity ratio of ITER Nb₃Sn strands

Influence of heat treatment excursion on critical current and residual resistivity ratio of ITER Nb₃Sn strands

Statistical analysis of the Nb₃Sn strand production for the ITER toroidal field coils