Abstract:Multifilament Nb 3 Sn superconductor has been produced by the internal tin tube (ITT) approach. The process employs tubular niobium filaments with cores consisting of tin or high tin alloy inside a copper sheath. The niobium annulus of each filament contained eight Nb-47Ti "islands." During the subsequent reaction heat treatments the titanium was diffused out of these islands and throughout the niobium annulus resulting in a calculated titanium concentration of 1.5 wt%. The process holds the promise to minimiz… Show more
“…Figure 18 ( [102]. One way to solve this problem is to move the Ti source away from the core (e.g., distributing Nb-47%Ti rods among the Nb alloy as in [105]).…”
Section: Prospects To Improve Pinning Capacitymentioning
confidence: 99%
“…Since oxide powder is preferably added to the core of each subelement for the ease of wire processing, introduction of Ti to the Sn core as in regular Nb3Sn wires would cause a reaction between Ti and O to form TiO2 [102]. One way to solve this problem is to move the Ti source away from the core (e.g., distributing Nb-47%Ti rods among the Nb alloy as in [105]).…”
Section: Prospects To Improve Pinning Capacitymentioning
Nb3Sn superconductors have significant applications in constructing high-field (> 10 T) magnets. This article briefly reviews development of Nb3Sn superconductor and proposes prospects for further improvement. It is shown that significant improvement of critical current density (Jc) is needed for future accelerator magnets. After a brief review of the development of Nb3Sn superconductors, the factors controlling Jc are summarized and correlated with their microstructure and chemistry. The non-matrix Jc of Nb3Sn conductors is mainly determined by three factors: the fraction of current-carrying Nb3Sn phase in the non-matrix area, the upper critical field Bc2, and the flux-line pinning capacity. Then prospects to improve the three factors are discussed respectively. An analytic model was developed to show how the ratios of precursors determine the phase fractions after heat treatment, based on which it is predicted that the limit of current-carrying Nb3Sn fraction in subelements is ~65%. Then, since Bc2 is largely determined by the Nb3Sn stoichiometry, a thermodynamic/kinetic theory was presented to show what essentially determines the Sn content of Nb3Sn conductors. This theory explains the influences of Sn sources and Ti addition on stoichiometry and growth rate of Nb3Sn layers. Next, to improve flux pinning, previous efforts in this community to introduce additional pinning centers (APC) to Nb3Sn wires are reviewed, and an internal oxidation technique is described.Finally, prospects for further improvement of non-matrix Jc of Nb3Sn conductors are discussed, 2 and it is seen that the only opportunity for further significantly improving Jc lies in improving the flux pinning.
“…Figure 18 ( [102]. One way to solve this problem is to move the Ti source away from the core (e.g., distributing Nb-47%Ti rods among the Nb alloy as in [105]).…”
Section: Prospects To Improve Pinning Capacitymentioning
confidence: 99%
“…Since oxide powder is preferably added to the core of each subelement for the ease of wire processing, introduction of Ti to the Sn core as in regular Nb3Sn wires would cause a reaction between Ti and O to form TiO2 [102]. One way to solve this problem is to move the Ti source away from the core (e.g., distributing Nb-47%Ti rods among the Nb alloy as in [105]).…”
Section: Prospects To Improve Pinning Capacitymentioning
Nb3Sn superconductors have significant applications in constructing high-field (> 10 T) magnets. This article briefly reviews development of Nb3Sn superconductor and proposes prospects for further improvement. It is shown that significant improvement of critical current density (Jc) is needed for future accelerator magnets. After a brief review of the development of Nb3Sn superconductors, the factors controlling Jc are summarized and correlated with their microstructure and chemistry. The non-matrix Jc of Nb3Sn conductors is mainly determined by three factors: the fraction of current-carrying Nb3Sn phase in the non-matrix area, the upper critical field Bc2, and the flux-line pinning capacity. Then prospects to improve the three factors are discussed respectively. An analytic model was developed to show how the ratios of precursors determine the phase fractions after heat treatment, based on which it is predicted that the limit of current-carrying Nb3Sn fraction in subelements is ~65%. Then, since Bc2 is largely determined by the Nb3Sn stoichiometry, a thermodynamic/kinetic theory was presented to show what essentially determines the Sn content of Nb3Sn conductors. This theory explains the influences of Sn sources and Ti addition on stoichiometry and growth rate of Nb3Sn layers. Next, to improve flux pinning, previous efforts in this community to introduce additional pinning centers (APC) to Nb3Sn wires are reviewed, and an internal oxidation technique is described.Finally, prospects for further improvement of non-matrix Jc of Nb3Sn conductors are discussed, 2 and it is seen that the only opportunity for further significantly improving Jc lies in improving the flux pinning.
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