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내부 확산법에 의한 Nb$_3Sn$ 초전도 선재에서 부분 가열이 초전도 특성에 미치는 영향
하동우,오상수,하홍수,이남진,권영길,류강식,Ha, Dong-Woo,Oh, Sang-Soo,Ha, Hong-Soo,Lee, Nam-Jin,Kwon, Young-Kil,Ryu, Kang-Sik 한국초전도저온공학회 2000 한국초전도저온공학회논문지 Vol.2 No.2
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.
Soun P. Kwon 한국초전도저온학회 2022 한국초전도저온공학회논문지 Vol.24 No.2
European efforts to design superconducting conductors for a future tokamak have involved Nb3Sn cable-in-conduit conductor(CICC). Nb3Sn coils which undergo heat treatment to activate the Nb3Sn material are mostly produced through the wind-thenreact route. However, some Nb3Sn coils have been proposed with CICCs of the react-then-wind route. The latter CICCs arephysically constrained due to handling limitations which if not adhered to will result in irrecoverable damage to the Nb3Sn cableinside, nullifying any performance advantage. A group at the Swiss Plasma Center has proposed such CICC designs, constructingsamples and testing them for performance. The characteristics and performance of these react & wind (R&W) CICCs arecompared with the more common wind & react (W&R) CICCs, and it is found that the R&W designs show more extremecharacteristics than typical W&R Nb3Sn CICCs for some parameters that are known to influence CICC performance. Where theR&W CICCs extend the range of those parameters, they also continue trends formed by the W&R CICCs with the parameters. The main observation, however, is that although the current sharing temperature performances of the R&W samples are above theaverage of the W&R samples they were compared to, they are not the highest. A similar observation applies to a cost comparisonof the superconducting material where the R&W CICCs are found to be relatively cheap but not the cheapest. Given these results,clear practical advantages to the R&W CICC design is not evident.
고 자장용 $Nb_3Sn$ 초전도체의 제조기술 및 응용
오상수,류강식 한국전기전자재료학회 1995 電氣電子材料學會誌 Vol.8 No.4
본 고에서는 Nb$_{3}$Sn 초전도선재의 대표적인 제조방법 및 원리 그리고 고자장마그네트 설계시 중요한 요소인 Nb$_{3}$Sn의 자장중 초전도특성 및 기계적특성 등에 대하여 고찰하고자 한다. 또한 Nb$_{3}$Sn 초전도선재의 응용분야로서 몇가지 대표적인 예를 들어 현재 세계적으로 활발하게 진행되고 있는 선진국의 고자장 초전도마그네트와 관련된 연구개발동향을 소개하고자 한다.
CICC manufacturing technology as a factor affecting on their performance during full-size testing
Kaverin, D. The Korea Institute of Applied Superconductivity a 2020 한국초전도저온공학회논문지 Vol.22 No.4
The test results of the ITER toroidal field conductors demonstrated a decrease of the current sharing temperature (Tcs) with an increase in the number of electromagnetic cycles in general. This is associating with several factors. One of them is the superconducting Nb3Sn filaments cracking and another one is the redistribution of the relative deformation of the Nb3Sn strands under Lorentz forces. Despite these factors, some conductors have shown the absence or significantly less degradation of Tcs during electromagnetic cycling. This article considers another possible reason for a more stable conductors Tcs behavior, namely, the local compression of Nb3Sn wires in the cross section of a conductor. In this article presents the results of a quantitative analysis Nb3Sn superconducting filaments cracking of strands extracted from a conductor that has passed electromagnetic cycling and the model of a conductor compaction, as well as calculation results based on this model are presented also.
Oh, S.,Park, S.H.,Lee, C.,Choi, H.,Kim, K. North-Holland 2010 Physica. C, Superconductivity Vol.470 No.2
A comparative study on the effects of heat treatment, especially, the duration of the A15 reaction temperature plateau on the strain dependence of the critical current for an internal-tin processed Nb<SUB>3</SUB>Sn strand has been carried out. The strain dependence of the critical current is measured by a variable temperature Walter spiral probe that we have developed. It was shown that prolonged heat treatment can be a very effective way to improve the strain dependency. For a quantitative analysis, the measured data were analyzed with various proposed scaling laws: the scaling law based on strong-coupling theory, the modified deviatoric strain scaling law, and the interpolative scaling law. We found that there is a slight increase in the critical temperature and a substantial improvement in the maximum pinning force. The origin of improved strain dependency is further discussed.
Suwa, Tomone,Nabara, Yoshihiro,Ozeki, Hidemasa,Hemmi, Tsutomu,Isono, Takaaki,Takahashi, Yoshikazu,Kawano, Katsumi,Oshikiri, Masayuki,Tsutsumi, Fumiaki,Shibutani, Kazuyuki,Nunoya, Yoshihiko,Okuno, Kiyo Institute of Electrical and Electronics Engineers 2015 IEEE transactions on applied superconductivity Vol.25 No.3
<P>Japan Atomic Energy Agency (JAEA) is procuring 100% of the ITER Central Solenoid (CS) conductors. The CS conductor is required to maintain the performance under 60000 pulsed electromagnetic cycles. JAEA tested two internal-tin Nb<SUB>3</SUB>Sn conductors for the CS at the SULTAN test facility. As a result of destructive examination, the twist pitches of both of the cables satisfied requirements of the ITER Organization (IO). The current sharing temperatures T<SUB>cs</SUB> of each sample were 6.6 and 6.8 K before cyclic operation, and the T<SUB>cs</SUB> values were 6.8 and 6.9 K after 9700 electromagnetic cycles, including three warm-up/cooldowns, respectively. The T<SUB>cs</SUB> performance of both samples satisfied the IO requirement. The ac losses of CSKO1-C and CSKO1-D were approximately half of typical bronze-route CS conductors at 2 and 9 T. The ac loss at 45.1 kA after the cycling was 1.5 times higher than that without the transport current. An almost constant strain of the jacket was observed after the test as a result of the residual strain measurement. Therefore, the deformation of the cable might have been homogeneous along the conductor axis. Because of the higher T<SUB>cs</SUB> of CSKO1-D than CSKO1-C, JAEA started the manufacturing of the CS conductor with the same specification as CSKO1-D.</P>
Kozo Osamura,Shutaro Machiya 한국초전도.저온공학회 2019 한국초전도저온공학회논문지 Vol.21 No.2
Practical superconducting wires are designed with a composite structure to meet the desired engineering characteristics by expert selection of materials and design of the architecture. In practice, the local strain exerted on the superconducting component influences the electromagnetic properties. Here, recent progress in methods used to measure the local strain in practical superconducting wires and conductors using quantum beam techniques is introduced. Recent topics on the strain dependence of critical current are reviewed for three major practical wires: Nb3Sn, BSCCO-2223 and REBCO tapes.
Osamura, Kozo,Machiya, Shutaro The Korea Institute of Applied Superconductivity a 2019 한국초전도저온공학회논문지 Vol.21 No.2
Practical superconducting wires are designed with a composite structure to meet the desired engineering characteristics by expert selection of materials and design of the architecture. In practice, the local strain exerted on the superconducting component influences the electromagnetic properties. Here, recent progress in methods used to measure the local strain in practical superconducting wires and conductors using quantum beam techniques is introduced. Recent topics on the strain dependence of critical current are reviewed for three major practical wires: $Nb_3Sn$, BSCCO-2223 and REBCO tapes.
김형찬,오동근,박수현,김기만,Kim, Hyoung-Chan,Oh, Dong-Keun,Park, Su-Hyeon,Kim, Kee-Man,Bruzzone, P. 한국초전도학회 2009 Progress in superconductivity Vol.10 No.2
As a participant taking part in the ITER TF conductor R&D program, we developed two toroidal field conductors with variations of conduit thickness resulting in the different void fraction of the conductors. The estimated void fractions of the conductors are 31% and 33%. In this paper we present the details of the TF conductor development and performance test results of them carried out by the measurement of current sharing temperature under cyclic loading. Regarding the conductor development, the internal-Sn-processed $Nb_3Sn$ strand characteristics, strand cabling, twist pitch and characteristics of the conduit materials are presented. For the understanding of the conductor design and performance, the conductor test results are presented and the effect of the conductor design parameters such as void fraction and twist pitch is discussed based on the results.
KSTAR PF 초전도자석의 크기 및 재료에 따른 결합손실 특성 분석
이현정,추용,이상일,박영민,박현택,오영국,Lee, H.J.,Chu, Y.,Lee, S.,Park, Y.M.,Park, H.T.,Oh, Y.K. 한국초전도저온학회 2009 한국초전도저온공학회논문지 Vol.11 No.3
It is important to predict AC loss in $Nb_3Sn$ and NbTi cable-in-conduit-conductor (CICC) reliably for the design and operation of large superconducting coils. The hysteresis loss in the superconducting filaments and coupling loss within strands and among strands in a cable or composite are dominant ac losses in superconducting magnets. The coupling loss in a superconductor can be characterized by identifying the coupling constant time $n{\tau}$. To reduce the coupling loss, all the strands (superconductor and Cu) in KSTAR (Korea Superconducting Tokamak Advance Research) are chromium plated with thickness of $l{\pm}0.5{\mu}m$. The ac losses of PF1, PF5 and PF6 coils has been measured by calorimetric method while applying trapezoidal current pulses with various ramp rate from 0.5 kA/s to 2 kA/s. The coupling time constants for $Nb_3Sn$ coils are $25{\sim}55$ ms and the values are not co-related with the coil size, the time constants for NbTi coil is 30 ms.