• Progress in Superconductivity and Cryogenics
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• v.2 no.2
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• pp.1-5
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• 2000

There is the possibility that internal tin processed Nb$_3Sn$ wires are locally heated during the drawing process and the jacketing process. It is important to know the variations in J$_c$ of internal tin processed Nb$_3Sn$ wires caused by local heating. Internal tin processed Nb$_3Sn$ rods were cold worked to 2.28 mm, using the appropriate reduction ratio, and then cut into several pieces. At this stage, wires were locally 50 mm heat zone heated up to 360$^{\circ}C$. The locally heated Nb$_3Sn$ wires were drawn to a final diameter size of 0.81 mm. Others were cold worked successively to 0.81 mm and locally heated with the same conditions. 2 types of locally heat treated wires were wound on Ti-6Al-4V barrels and heat treated for the Nb$_3Sn$ reaction. Local heating of internal tin processed Nb$_3Sn$ wires after the J$_c$ of these wires. However, local heating at an intermediate stage of the drawing process caused a decrease in J$_c$. When the local heating temperatures were higher than melting point of Sn, non-Cu J$_c$'s decreased significantly. A Sn-Cu alloyed boundary appeared after local heating over the melting point of Sn, and caused work hardening and a decrease in the workability.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.496-499
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• 2000

In order to investigate the effect of Ge addition to the Cu Matrix on the microstructure and the critical current density, four kinds of internal tin processed Nb$_3$Sn strands with pure Cu and Cu 0.2, 0.4, 0.6 wt％ Ge alloy were drawn to 0.8 mm diameter. The microstructure and critical current of internal tin processed Nb$_3$Sn wires that were heat treated at temperatures ranging from 68$0^{\circ}C$ to 74$0^{\circ}C$ for 240 h were investigated. The Ge addition to the matrix did not make workability worse. A Ge rich layer in the Cu-Ge matrix suppressed the growth of the Nb$_3$Sn layer and promoted grain coarsening. The greater the Ge content in the matrix, the lower the net Jc result after Nb$_3$Sn reaction heat treatment. There was no significant variation in Jc observed with heat treatment temperature ranging from 68$0^{\circ}C$ to 74$0^{\circ}C$.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 1999.02a
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• pp.14-17
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• 1999

Four designed $Nb_{3}$Sn superconductors have been fabricated in order to investigate the effect of pre-heat treatment for internal tin process. 3 types of sub-elements and 2 types of Sn reservers were fabricated. Diffusion of Sn is better in the strand divided Sn equally than in the strand had one large Sn reserver during pre heat-treatment.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1472-1474
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• 1997

In this study, the $Nb_3Sn$ wire was tried to fabricate by internal tin process to investigate the relationship between the processing parameters in a cold working and the microstructure. The critical current densities of $Nb_3Sn$ wires were evaluated in magnetic fields at 4.2 K. $Nb_3Sn$ compound layer was found to be formed between Nb core and Cu-Sn. The Cu part in the wire transformed to Cu-Sn by the reaction with Sn and the Sn in the Cu-Sn part reacted with Nb.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1556-1558
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• 1999

$Nb_3Sn$ superconducting wires were fabricated in order to investigate the effect of pre-heat treatment for internal tin process. 2 types of Sn reservoir were fabricated. One was arranged one large Sn reservoir in the center of wire, the other arranged several Sn reservoirs inthe wire. Diffusion of Sn is better in the strand divided Sn equally than in the strand had one large Sn reservoir during pre heat-treatment. Critical current was better in the wires divided Sn reservoirs uniformly after whole heat treatment.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.104-107
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• 2001

In order to investigate the effect of Ge addition to the Cu matrix on the microstructure and the critical current density, four kinds of internal tin processed Nb$_3$Sn strands with pure Cu and Cu 0.2, 0.4, 0.6 wt % Ge alloys were drawn to 0.8 mm diameter. The microstructure and critical current of internal tin processed Nb$_3$Sn wires that were heat treated at temperatures ranging from 68$0^{\circ}C$ to 74$0^{\circ}C$ for 240h were investigated. The Ge addition to the matrix did not make workability worse. A Ge rich layer in the Cu-Ge matrix suppressed the growth of the Nb$_3$Sn layer and promoted grain coarsening. The greater the Ge content in the matrix, the lower the net Jc result after Nb$_3$sn reaction heat treatment. There was no significant variation in Jc observed with heat treatment temperature ranging from 68$0^{\circ}C$ to 74$0^{\circ}C$. The values of AC loss of Ge added wires were decreased to 40 % compare with no addition wire. Low AC loss was due to segregation of Ge rich layer in the Cu-Ge matrix. If Ge added wire with thin Nb filaments were fabricated, slow diffusion rate of Sn would be overcome and decreased AC loss that is weak Point of internal tin method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.806-809
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• 2000

A key technology for achieving commercial Nb$_3$Sn superconducting wires may be driven from fabrication Process of big-scale billets. Sub-element billet with diameter of 200 mm was designed and fabricated. This billet was hot-extruded and drawn. Cu stabilizer tube, Nb barrier tube and 19 sub-elements inserted Sn core were composed for strand. There was no breakage in the strand that was constituted with annealed sub-element. It was need that billet had to treat HIP because of remove of voids and goad contact between Cu and Nb filaments. Ta wound sheet was better than Ta tube thor barrier in the strand. Ic of the Nb$_3$Sn wire at 127, 4.2K was over than 120 A.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.11
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• pp.1022-1026
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• 1998

The mutifilamentary $Nb_3$Sn wire containing 135 Nb filaments was manufactured by the internal tin method. The critical current density ($J_C$) in magnetic fields for the wires heat-treated at $660^{/circ}C$ and $700^{/circ}C$ were investigated. The Non-Cu $J_C$ and n-value of 0.82 mm$\phi$ $Nb_3$Sn wire heat-treated at $700^{/circ}C$ for 240 hours was approximately 450 A/$mm^2$ at 12T, 4.2K and 14, respectively. Also the $B_{C2}$ of $Nb_3$Sn wire extrapolated by Kramer plot was 27.2T. The wire heat-treated at $700^{/circ}C$ for 240 hours showed smaller residual tin concentration in the matrix and the larger area of $Nb_3$Sn layer as comparison with the wire heat-treated at $660^{/circ}C$.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.876-878
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• 1999

Internal tin processed Nb3Sn wires with different diameter were locally heated before reaction heat treatment. Local heating at the intermediate state of drawing process decreased the superconducting properties and workability. When the local heating temperatures were higher than melting point of Sn, non-Cu Jc's decreased significantly.

• Progress in Superconductivity and Cryogenics
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• v.18 no.3
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• pp.10-20
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• 2016

The Cable-In-Conduit-Conductor (CICC) for the ITER tokamak Central Solenoid (CS) has undergone design change since the first prototype conductor sample was tested in 2010. After tests showed that the performance of initial conductor samples degraded rapidly without stabilization, an alternate design with shorter sub-cable twist pitches was tested and discovered to satisfy performance requirements, namely that the minimum current sharing temperature ($T_{cs}$) remained above a given limit under DC bias. With consistent successful performance of ITER CS conductor CICC samples using the alternate design, an attempt is made here to revisit the internal electromagnetic properties of the CICC cable design to identify any correlation with conductor performance. Results of this study suggest that there may be a simple link between the $Nb_3Sn$ CICC internal self-field and its $T_{cs}$ performance. The study also suggests that an optimization process should exist that can further improve the performance of $Nb_3Sn$ based CICC.