Abstract
We present a model for the variation of the upper critical field Hc2 with Sn content in A15-type Nb-Sn wires, within the Ginzburg-Landau-Abrikosov-Gor’kov (GLAG) theory frame. Hc2 at the vicinity of the critical temperature Tc is related quantitatively to the electrical resistivity ρ, specific heat capacity coefficient γ and Tc. Hc2 versus tin content is theoretically formulated within the GLAG theory, and generally reproduces the experiment results. As Sn content gradually approaches the stoichiometry, A15-type Nb-Sn undergoes a transition from the dirty limit to clean limit, split by the phase transformation boundary. The H-T phase boundary and pinning force show different behaviors in the cubic and tetragonal phase. We dipict the dependence of the composition gradient on the superconducting properties variation in the A15 layer, as well as the curved tail at vicinity of Hc2 in the Kramer plot of the Nb3Sn wire. This helps understanding of the inhomogeneous-composition inducing discrepancy between the results by the state-of-art scaling laws and experiments.
Highlights
At present, conventional low-temperature superconductors such as Nb3Sn have been extensively applied in high-energy and nuclear physics, as well as in magnetic resonance imaging systems[1]
The scaling field for the critical current reflects the average properties over the wire volume; it relates to the local variation of the critical field dependent on the composition gradient[10]
Cooley and the coauthors simulate the effect of Sn composition gradients on the superconducting properties of powder-in-tube (PIT) Nb3Sn strand, with an ideal structure modeled by concentric shells with varying Sn content[7]
Summary
The calculation results are impressive (Fig. 4): Bc2(0) obtained by Bc2(T0) with EP correction and extrapolated by MDG relation (EP + MDG) is in good agreement with the experiments This validates the above GLAG descriptions, and the MDG description for the temperature dependence of the upper critical field at any composition over the A15 phase field. (1) and (11)] is much higher than the experimental curve and has no restriction to Bc2(0) This is consistent with the view by Orlando et al.[19], who demonstrate that EP corrected PPL has nothing to do with Nb3Sn superconductivity, since the strong EP interaction in Nb3Sn increases largely the Pauli limiting field above its BCS value and the spin-orbit scattering is less involved. This explains why we only take the impurity scattering into account while exclude the spin-orbit scattering
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
