• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.6
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• pp.1035-1038
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• 2007

We designed and manufactured a 1.8T high temperature superconducting(HTS) insert coil for a NMR magnet operated at 4.2 K. Suitable HTS superconductor and HTS coil were carefully designed and developed. We have selected multi-filamentary Bi2223 conductor fabricated by American Superconductor Corporation(AMSC). The selected conductor consists of Bi2223 filaments of 55, silver stabilizer and stainless steel reinforcement tapes. Therefore, it shows good hoop strength as well as compression tolerance. The conductor has a tape cross-section of 0.31mm x 4.8mm. the Bi2223 conductor shows large anisotropy of critical current. The critical current of conductor in magnetic field parallel to the flat surface are much higher than that in magnetic field perpendicular. The HTS coil has an inner diameter of 78 mm, an outer diameter of 127 mm and a coil length of 600 mm. In this paper, the detailed design, fabrication and test results on the HTS insert coil are presented.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.91-94
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• 2002

The conditions of zone-melting method such as a sample travel speed in a furnace, content of Nd422, control of melting temperature, and heat-treatment with/without Ar gas for $NdBa_{2}Cu_{3}O_{7-\delta}$ superconductor was optimized, As a results, a $NdBa_{2}Cu_{3}O_{7-\delta}$ sample with a surface area of $25mm^{2}$ showed a good superconducting properties when its travel speed was 6 mm/h, The improvement of superconductivity added with 10~20 wt% of Nd422 phase increasing pinning effect was also shown. The critical current density, $J_{c}$ was remarkable affected by the condition of heat-treatment temperature of $NdBa_{2}Cu_{3}O_{7-\delta}$superconductor with/without Ar ambient gas.

• Journal of Magnetics
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• v.1 no.1
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• pp.42-45
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• 1996

We have studied the superconductivity of rapidly quenched $YPd_2B_2C$ ribbons. The superconductivity in bulk $YPd_2B_2C$ is completely suppressed by annealing as-cast ingots at hihger temperature, suggesting that the superconducting phase is metastable. The rapidly quenched sample, in the as-quenched state, shows the superconducting transition temperature of about 21 K. Form our magnetic data, the value for the upper critical field $H_c2$ (0) is estimated to be 10 T. The critical current density and the expected specific heat discontinuity $({\Delta}C/{\gamma}{T_c})$ were obtained to be about$10^8A/m^2$ at 10 Oe and 1.55, respectively.

• Progress in Superconductivity and Cryogenics
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• v.8 no.3
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• pp.49-53
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• 2006

A high temperature superconductor (HTS) has been developed for power applications such as power cables, fault current limiters and superconducting magnetic energy storage devices. For such applications it is required to understand the DC voltage-current characteristic of the HTS. which is important in analyzing AC loss and flux flow loss quantitatively. In this work, we have experimentally investigated influence of several factors, e.g. critical current density. degradation and AC external magnetic field, on the DC voltage-current characteristic. The measured results have been discussed in engineering application point of view.

• Electrical & Electronic Materials
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• v.10 no.9
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• pp.869-875
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• 1997

Bi based superconducting thin films were fabricated by 4-target RF magnetron sputtering using the method of controlling the on-off time. These thin films showed better crystal structures. The ratio of Cu/Bi decreased but the critical temperature increased with increasing the temperature of the substrate. High temperature phase low temperature of the substrate. High temperature phase low temperature phase and semiconducting phase can be formed by controlling the on-off time of the shutter respectively.

• Electrical & Electronic Materials
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• v.7 no.4
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• pp.306-311
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• 1994

In this study, the influence of the powder sintering, the 2nd sinteiing and the grinding time on the Superconducting properties in the Bi(Pb)SiCaCuO Superconductor has been studied. From the analysis of SEM and XRD patterns, it was known that the sample prepared by the process of powder sintering has a porous microstructure with the critical temperature(Tc) below 77K, while the sample prepared by the 2nd sintering has a highly oriented microstructure with the Tc above 100K. The Critical Current Density(Jc) of the sample prepared by the 2nd sintering was better than the sample prepared by the process of powder sinteiing, but it's Jc, was low in practical use. Also, the effect of grinding time from 0[min] to 120[min] was investigated. As the grinding time is increased, the samples degraded from high-Tc phase to low-Tc phase and nonsuperconducting phases.

• Progress in Superconductivity and Cryogenics
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• v.4 no.1
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• pp.78-83
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• 2002

Since the KSTAR superconducting magnet structure should be maintained at a cryogenic temperature of about 4 K, even a small amount of heat might be a major cause of the temperature rise of the structure. The Joule heating by eddy currents induced in the magnet structure during the KSTAR operation was found to be a critical parameter for designing the cooling scheme of the magnet structure as well as defining the requirements of the refrigerator for the cryogenic system. Based on the Joule heating calculation, it was revealed that the bulk temperature rise of the magnet coil structure was less than 1 K. The local maximum temperature especially at the inboard leg of the TF coil structure increased as high as about 21 K for the plasma vertical disruption scenario. For the CS coil structure, the maximum temperature was obtained from the PF fast discharging scenario. This means that the vertical disruption and PF fast discharging scenarios are the major scenarios for the design of TF and CS coil structures, respectively. For the reference scenario, the location of maximum temperature spot changes according to the transient current variation of each PF coil.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.790-793
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• 2000

We have fabricated good quality superconducting YBa$_2$Cu$_3$$O_{7-x}$(YBCO) thin films on Hastelloy(Ni-Cr-Mo alloys) metallic substrates with CeO$_2$and BaTiO$_3$buffer layers in-situ by pulsed laser deposition in a multi-target processing chamber. YBCO film with CeO$_2$ single buffer layer shows T$_{c}$ of 71.64 K and the grain size less than 0.1 ${\mu}{\textrm}{m}$. When BaTiO$_3$is used as a single buffer layer, the grain size of YBCO is observed to be larger than that of YBCO/CeO$_2$by 200 times and the transition temperature of the film is enhanced to be about 84 K. CeO$_2$/BaTiO$_3$double buffer layer has been adopted to enhance the superconducting properties, which results in the enhancement of the critical temperature and the critical current density to be about 85 K and 8.4 $\times$ 10$^4$ A/cm$^2$ at 77 K, respectively mainly due to the enlargement of the grain size of YBCO film.ilm.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.11
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• pp.959-962
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• 2000

We have fabricated good quality superconducting YBa$_2$Cu$_3$$O_{7-x}$(YBCO) thin films on Hastelloy(Ni-Cr-Mo alloys) metallic substrates with CeO$_2$and BaTiO$_3$buffer layers in-situ by pulsed laser deposition in a multi-target processing chamber. YBCO film with CeO$_2$single buffer layer shows T$_{c}$ of 71.64 K and the grain size less than 0.1${\mu}{\textrm}{m}$. When BaTiO$_3$ is used as a single buffer layer, the grain size of YBCO is observed to be larger than that of YBCO/CeO$_2$by 200 times and the transition temperature of the film is enhanced to be about 84 K. CeO$_2$/BaTiO$_3$double buffer layer has been adopted to enhance the superconducting properties, which results in the enhancement of the critical temperature and the critical current density to be about 85 K and 8.4$\times$10$^4$ A/$\textrm{cm}^2$ at 77 K, respectively mainly due to the enlargement of the grain size of YBCO film.ilm.

• Progress in Superconductivity and Cryogenics
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• v.23 no.2
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• pp.24-27
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• 2021

This paper presents a design methodology of high-temperature superconducting (HTS) magnets. The magnet consists of several double pancake coils with a variety of wire width. This technique, named Multi-Width, is well known to make efficient use of the superconducting wire. It is common for design of high-temperature superconducting magnets to not only reduce wire consumption used, but also consider the homogeneity of the magnetic field. In this paper, we study a design method that efficiently reduces wire usage while considering magnetic field homogeneity. The design is carried out by calculating the critical current and the critical magnetic field according to the configuration of arranging the thickness of the wire to determine the number of windings. The width of wire comprising the magnet was set to 4 - 12 mm, and the number of double pancake coils was set to an even number to consist of top-down symmetry. To verify the validity of the design, we compared the progress of the design code with a complete enumeration survey. As a case study, we designed a magnet that generates a central magnetic field of 3 T or more in a 240 mm bore in diameter. Optimality can be evaluated by weighing wire consumption and field homogeneity according to the magnet's use or user preference.