Analysis of inhomogeneities in Nb3Sn wires by combined SEM and SHPM and their impact on J
 c and T
 c

Pfeiffer, Stephan; Baumgartner, T.; Löffler, Stefan; Stöger‐Pollach, Michael; Hopkins, Simon C.; Ballarino, A.; Eisterer, M.; Bernardi, Johannes

doi:10.1088/1361-6668/acb857

Cited by 5 publications

(20 citation statements)

References 16 publications

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“…To ensure all the outer Nb barrier layer was removed from the irradiated samples before shaping APT tips, EDX analysis was used to measure the amount of Nb which had to be milled away from the external surface of the subelement. In RRP ® wires there has previously been shown to be a weak Sn gradient in concentration through the reacted Nb 3 Sn layer [30]. Taking this into account, APT needles from both the as-received and irradiated samples were taken from similar regions towards the outer edge of the Nb 3 Sn layer, and we expect them to have comparable Sn contents.…”

Section: Samples For Aptmentioning

confidence: 99%

Understanding the nanoscale chemistry of as-received and fast neutron irradiated Nb₃Sn RRP^® wires using atom probe tomography

Wheatley

Baumgartner

Eisterer

et al. 2023

Supercond. Sci. Technol.

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Atom Probe Tomography has been used to study the effect of fast neutron irradiation on the local chemistry of Nb3Sn samples. Two RRP® wires doped with 2 at% Ti were analysed, one in the as-received condition and the other irradiated to a neutron fluence (E>0.1MeV) of 2.82x1022 m-2 in the TRIGA-II reactor. The irradiated sample had a reduced Tc, an increase in Fp, a shift in the peak of the Fp curve suggesting the introduction of secondary point pinning, and an increase in the estimated scaling field B*. Atom Probe Tomography analysis has shown that polycrystalline Nb3Sn has three distinct regions of composition, near stoichiometry Nb3Sn (low Nb), regions with a higher Nb content than expected in equilibrium Nb3Sn (high Nb) and grain boundaries. The summed composition of these three regions lies within the Nb3Sn phase for both the as-received and irradiated samples. The distinct regions of high Nb Nb3Sn demonstrate incomplete diffusion in the as-received sample, and the reduction in volume of these high Nb regions after irradiation implies significant radiation induced diffusion has occurred. The occurrence presence of other features in the atomic-scale chemistry, such as the extent of Cu segregation at grain boundaries, and to three types of dislocation array, and unreacted Nb nanoparticles, are compared between samples.

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Section: Samples For Aptmentioning

confidence: 99%

Understanding the nanoscale chemistry of as-received and fast neutron irradiated Nb₃Sn RRP^® wires using atom probe tomography

Wheatley

Baumgartner

Eisterer

et al. 2023

Supercond. Sci. Technol.

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“…In Figure 5, we fitted this largest publicly available dataset for Nb3Sn conductors fabricated using bronze technology to Equation (15). The deduced parameters were |𝐹 𝑝,𝑚𝑎𝑥 (0)| = 74 ± 3 GN m 3 , and 𝛿 = 175 ± 12 nm .…”

Section: Bronze Technology Samplesmentioning

confidence: 99%

“…The parameters have low dependence (~ 0.87), which indicates that our model (Equation ( 15)) is not over-parameterized. (15). Raw data reported by Marken [42], West et al [43], Fischer [40], Shaw [44], Schauer et al [45], and Scanlan et al [46].…”

Section: Bronze Technology Samplesmentioning

confidence: 99%

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Characteristic Length for Pinning Force Density in Nb3Sn

Talantsev¹,

Valova-Zaharevskaya²,

Deryagina³

et al. 2023

Preprint

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The pinning force density FpJc,B=Jc×B (where Jc is the critical current density and B is the applied magnetic field) is one of the main parameters that characterize the resilience of a superconductor to carry a dissipative-free transport current in an applied magnetic field. Kramer (1973 J. Appl. Phys. 44 1360), and Dew-Hughes (1974 Phil. Mag. 30 293) proposed a widely used scaling law for the pinning force density amplitude: FpB=Fp,max×p+qp+qppqq×BBc2p×1-BBc2q, where Fp,max, Bc2, p, and q are free-fitting parameters. Since the late 1970-s till now, several research groups have reported experimental data on the dependence of Fp,max on the average grain size, d, in Nb3Sn-based conductors. Godeke (2006 Supercond. Sci. Techn. 19 R68) proposed that the dependence obeys the law Fp,maxd=A×ln1d+B. However, this scaling law has several problems, for instance, the logarithm is taken from a non-dimensionless variable, and Fp,maxd&lt;0 for large grain sizes, and Fp,maxd→∞ for d→0. Here, we reanalysed the full inventory of publicly available Fp,maxd data for Nb3Sn conductors and found that the dependence can be described by Fp,maxd=Fp,max0×exp-dδ law, where the characteristic length, δ, varies within a remarkably narrow range, that is, δ=175±13 nm, for samples fabricated by different technologies. The interpretation of the result is based on the idea that the in-field supercurrent flows within a thin surface layer (thickness of δ) near the grain boundary surfaces (similar to London’s law, where the self-field supercurrent flows within a thin surface layer with a thickness of the London penetration depth, λ, and the surface is a superconductor-vacuum surface). An alternative interpretation is that δ represents the characteristic length of the exponential decay flux pinning potential from the dominant defects in Nb3Sn superconductors, which are grain boundaries.

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“…It is assumed that this tin variation is a non-negligible contribution to the disagreement between the scaling laws and the experimental results. To improve the scaling law it is useful to understand how B c2 varies with Sn content (see [21][22][23] for recent advances in composition dependences of superconducting properties), since a Nb 3 Sn conductor has practically tin composition content that covers the full range of A15 phase (generally thought to range from ∼18-25 at.% Sn). Following the approach proposed by the same author [24], we begin with the dependence of GL (Ginzburg-Landau) parameters k on the three independent material parameters that are the transport scattering resistivity r W , m low-temperature coefficient of electronic heat capacity g mJ and transition temperature T c [25].…”

Section: Introductionmentioning

confidence: 99%

A semi-empirical formula for the dependence of upper critical field with component and strain in Nb₃Sn

Xu,

Li,

Salmi

2023

Phys. Scr.

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We include the effects of Sn content β in the scaling law to generalize the upper critical field B c 2 ( T , ε ) function of temperature and strain in Nb3Sn. The basis for this generalization comes from a theory developed by the same author [Scientific Reports 7, 1133 (2017)]. The important assumption in the current work is that, in determining the upper critical field B c 2 , the contributions of strain, temperature and Sn content are independent of each other. It is followed that we write down a semi-empirical expression B c 2 ( T , ε , β ) = B c 2 ( T 0 , ε 0 , β ) s ( ε ) ( 1 − t 1.52 ) where the strain function s ( ε ) and t ≡ T / T c ( ε ) are affected only by strain and temperature, respectively, and the variation of tin content β enters in the function B c 2 through B c 2 ( T 0 , ε 0 , β ) . This separable form of B c 2 ( T , ε , β ) allows one to incorporate Sn content β in the scaling law in a natural way, while this variable is not considered by traditional scaling laws. In addition to this advance, one can see a more flexible function with triple variables which could be an effective tool to fit or predict experiments. As the last but most important outcome, this semi-empirical function instructs one how to understand the role of component content played in scaling behaviors of Nb3Sn, so as to reduce the off-stoichiometric composition inducing discrepancy between the results by scaling laws and experiments.

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Analysis of inhomogeneities in Nb₃Sn wires by combined SEM and SHPM and their impact on J _c and T _c

Cited by 5 publications

References 16 publications

Understanding the nanoscale chemistry of as-received and fast neutron irradiated Nb₃Sn RRP^® wires using atom probe tomography

Understanding the nanoscale chemistry of as-received and fast neutron irradiated Nb₃Sn RRP^® wires using atom probe tomography

Characteristic Length for Pinning Force Density in Nb3Sn

A semi-empirical formula for the dependence of upper critical field with component and strain in Nb₃Sn

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Analysis of inhomogeneities in Nb3Sn wires by combined SEM and SHPM and their impact on J c and T c

Cited by 5 publications

References 16 publications

Understanding the nanoscale chemistry of as-received and fast neutron irradiated Nb3Sn RRP® wires using atom probe tomography

Understanding the nanoscale chemistry of as-received and fast neutron irradiated Nb3Sn RRP® wires using atom probe tomography

Characteristic Length for Pinning Force Density in Nb3Sn

A semi-empirical formula for the dependence of upper critical field with component and strain in Nb3Sn

Contact Info

Product

Resources

About

Analysis of inhomogeneities in Nb₃Sn wires by combined SEM and SHPM and their impact on J _c and T _c

Understanding the nanoscale chemistry of as-received and fast neutron irradiated Nb₃Sn RRP^® wires using atom probe tomography

Understanding the nanoscale chemistry of as-received and fast neutron irradiated Nb₃Sn RRP^® wires using atom probe tomography

A semi-empirical formula for the dependence of upper critical field with component and strain in Nb₃Sn