PLD법을 이용한 TmBa₂Cu₃O<SUB>7-x</SUB> 초전도 선재 제작 및 전류전송특성 평가

권오정(O-Jong Kwon),고락길(Rock-Kil Ko),구현(Hyun Koo),배성환(Sung-Hwan Bae),정명진(Myung-Jin Jung),오상수(Sang-Soo Oh),박찬(Chan Park) 대한전기학회 2009 전기학회논문지 Vol.58 No.11

REBa₂Cu₃O7-d(REBCO) coated conductors(REBCO CCs) have been studied for electric power applications which require high current density wires. As long as the critical transition temperature(Tc) is concerned, REBCO CCs with large RE³? ions have been expected to have better current transport properties than those with smaller RE³? ions. For this reason, REBCO's with large RE³? ions which include GdBCO, NdBCO and SmBCO have been mainly considered as the superconducting layer of CCs. On the other hand, REBCO's with smaller RE³? ions are expected to have advantages in the fabrication process of CCs because of the lower melting temperature. But it has not yet been made clear which REBCO is the most suitable for the superconducting layer of CCs. In this study, we investigated the current transport properties of REBCO CCs with small RE³? ion and advantages of using that in the CC fabrication process. Thin films of TmBCO, which has smaller RE³? ion than most other RE³? ions, were fabricated on buffered metal substrate as the superconducting layer of CC by PLD process. TmBCO CC shows critical current density (Jc (77 K, sf) = 2.3 MA/㎠) high enough to be utilized for application in electric power devices. Compared with previous experiments using the same PLD system, deposition temperature was approximately 20 ℃ lower than NdBCO thin films on buffered metal substrates.

Conceptual design of 240 mm 3 T no-insulation multi-width REBCO magnet

Kibum Choi,Jung Tae Lee,Jeseok Bang,Uijong Bong,Jeonghwan Park,Seungyong Hahn 한국초전도.저온공학회 2019 한국초전도저온공학회논문지 Vol.21 No.3

A rare-earth barium copper oxide (REBCO) superconducting magnet was designed using no-insulation (NI) and multi-width (MW) winding techniques. The proposed magnet is comprised of 58 REBCO-wound single pancake coils with a bore size of 240 mm. When the magnet is operated at 20 K, the center magnetic flux density is designed to reach 3 T with an operational current of 169.55 A, 70 % of its critical current. The critical current was evaluated using experimental data of a short REBCO conductor sample. The designed magnet was then simulated using FEM software with uniform current density model. Magnetic field and mechanical properties of the magnet are evaluated using the simulated data. This magnet was designed as one of the base designs for the project “Tesla-Level Magnets with Large Bore Sizes for Industrial Applications” which was initiated in 2019, and will be wound using REBCO wires with the defect-irrelevant-winding (DIW) technique incorporated to reduce the overall manufacturing cost.

Conceptual design of 240 mm 3 T no-insulation multi-width REBCO magnet

Choi, Kibum,Lee, Jung Tae,Bang, Jeseok,Bong, Uijong,Park, Jeonghwan,Hahn, Seungyong The Korea Institute of Applied Superconductivity a 2019 한국초전도저온공학회논문지 Vol.21 No.3

A rare-earth barium copper oxide (REBCO) superconducting magnet was designed using no-insulation (NI) and multi-width (MW) winding techniques. The proposed magnet is comprised of 58 REBCO-wound single pancake coils with a bore size of 240 mm. When the magnet is operated at 20 K, the center magnetic flux density is designed to reach 3 T with an operational current of 169.55 A, 70 % of its critical current. The critical current was evaluated using experimental data of a short REBCO conductor sample. The designed magnet was then simulated using FEM software with uniform current density model. Magnetic field and mechanical properties of the magnet are evaluated using the simulated data. This magnet was designed as one of the base designs for the project "Tesla-Level Magnets with Large Bore Sizes for Industrial Applications" which was initiated in 2019, and will be wound using REBCO wires with the defect-irrelevant-winding (DIW) technique incorporated to reduce the overall manufacturing cost.

R&D trends of high current REBCO conductor

오상수 한국초전도저온학회 2022 한국초전도저온공학회논문지 Vol.24 No.1

So far, large-scale scientific devices such as nuclear fusion tokamaks and high energy circular accelerators were constructed using high-current conductors made of metallic superconducting wires. Recently, as REBCO superconducting wires usable in high magnetic fields have been developed by several companies, researches to apply high current cable type REBCO conductors to next-generation large superconducting magnets were also started. High critical currents of several kA or more in high magnetic fields have been successfully demonstrated on test samples of REBCO cable conductors by several research groups. In this review article, the main features and properties of the representative high current REBCO conductors such as CORC(Conductor On Round Core), TSTC(Twisted Stacked-Tape Cable) and RACC(Roebel-Assembled Coated Conductor), which are currently being developed at abroad are briefly introduced. Research activities of high-current density REBCO MHOS(Multi HTS layers on One Substrate) conductor at KERI, whose structure is different from other cable type REBCO conductors are also shortly introduced.

Current overshoot operation of a REBCO magnet to mitigate SCF

Lee, Changhyung,Hahn, Seungyong,Bang, Jeseok,Cho, Jeonwook,Kim, Seokho The Korean Society of Superconductivity and Cryoge 2018 한국초전도저온공학회논문지 Vol.20 No.4

Due to large in-field current carrying capacity and strong mechanical strength, a REBCO wire has been regarded as a viable high temperature superconductor (HTS) option for high field MRI and > 1 GHz (>23.5 T) NMR magnets. However, a REBCO magnet is well known to have an inherent problem of field inhomogeneity, so-called 'Screening Current induced magnetic Field (SCF)'. Recently, 'field shaking' and 'current overshoot operation' techniques have been successfully demonstrated to mitigate the SCF and enhance the field homogeneity by experiments. To investigate the effectiveness of current overshooting operation technique, a numerical simulation is conducted for a test REBCO magnet composed of a stack of double pancake coils using '2D edge-element magnetic field formulation' combined with 'domain homogenization' scheme. The simulation result demonstrates that an appropriate amount of current overshoot can negate the SCF. To verify the simulation results, current overshoot experiments are conducted for the REBCO magnet in liquid nitrogen. Experimental results also demonstrate the possible application of current overshoot technique to mitigate the SCF and enhance the field homogeneity.

Current overshoot operation of a REBCO magnet to mitigate SCF

이창형,한승용,방재석,조전욱,김석호 한국초전도.저온공학회 2018 한국초전도저온공학회논문지 Vol.20 No.4

Due to large in-field current carrying capacity and strong mechanical strength, a REBCO wire has been regarded as a viable high temperature superconductor (HTS) option for high field MRI and > 1 GHz (>23.5 T) NMR magnets. However, a REBCO magnet is well known to have an inherent problem of field inhomogeneity, so-called ‘Screening Current induced magnetic Field (SCF)’. Recently, ‘field shaking’ and ‘current overshoot operation’ techniques have been successfully demonstrated to mitigate the SCF and enhance the field homogeneity by experiments. To investigate the effectiveness of current overshooting operation technique, a numerical simulation is conducted for a test REBCO magnet composed of a stack of double pancake coils using ‘2D edge-element magnetic field formulation’ combined with ‘domain homogenization’ scheme. The simulation result demonstrates that an appropriate amount of current overshoot can negate the SCF. To verify the simulation results, current overshoot experiments are conducted for the REBCO magnet in liquid nitrogen. Experimental results also demonstrate the possible application of current overshoot technique to mitigate the SCF and enhance the field homogeneity.

Evaluation of electromechanical properties in REBCO CC tapes under transverse compression using anvil test method

Diaz, Mark Angelo,Shin, Hyung-Seop The Korean Society of Superconductivity and Cryoge 2022 한국초전도저온공학회논문지 Vol.24 No.3

One of the major applications of REBCO coated conductor (CC) tapes is in superconducting magnets or coils that are designed for high magnet fields. For such applications, the CC tapes were exposed to a high level of stresses which includes uniaxial tensile or transverse compressive stresses resulting from a large magnetic field. Thus, CC tapes should endure such mechanical load or deformation that can influence their electromechanical performance during manufacturing, cool-down, and operation. It has been reported that the main cause of critical current (I_c) degradation in CC tapes utilized in coil windings for superconducting magnets was the delamination due to transversely applied stresses. In most high-magnetic-field applications, the operating limits of the CC tapes will likely be imposed by the electromechanical properties together with its I_c dependence on temperature and magnetic field. In this study, we examined the influence of the transverse compressive stress on the I_c degradation behaviors in various commercially available CC tapes which is important for magnet design Four differently processed REBCO CC tapes were adopted to examine their I_c degradation behaviors under transverse compression using an anvil test method and a newly developed instantaneous I_c measurement system. As a result, all REBCO CC tapes adopted showed robustness against transverse compressive stresses for REBCO coils, notably at transverse compressive stresses until 250 MPa. When the applied stress further increased, different Ic degradation behaviors were observed depending on the sample. Among them, the one that was fabricated by the IBAD/MOCVD process showed the highest compressive stress tolerance.

Effects of seed geometry on the crystal growth and the magnetic properties of single grain REBCO bulk superconductors

Lee, Hwi-Joo,Park, Soon-dong,Jun, Bung-Hyuck,Kim, Chan-Joong,Lee, Hee-Gyoun The Korea Institute of Applied Superconductivity a 2017 한국초전도저온공학회논문지 Vol.19 No.3

This study presents that the orientation and the geometry of seed affect on the growth behavior of melt processed single grain REBCO bulk superconductor and its magnetic properties. The effects of seed geometry have been investigated for thin $30mm{\times}30mm$ rectangular powder compacts. Single grain REBCO bulk superconductors have been grown successfully by a top seed melt growth method for 8-mm thick vertical thin REBCO slab. Asymmetric structures have been developed at the front surface and at the rear surface of the specimen. Higher magnetic properties have been obtained for the specimen that c-axis is normal to the specimen surface. The relationships between microstructure, grain growth and magnetic properties have been discussed.

REBCO 초전도 박막제조를 위한 Fluorine-free MOD 전구체 용액 개발

김병주,임선원,김호진,홍계원,이희균,Kim, Byeong-Joo,Lim, Sun-Weon,Kim, Ho-Jin,Hong, Gye-Won,Lee, Hee-Gyoun 한국초전도학회 2006 Progress in superconductivity Vol.7 No.2

New precursor solution with dichloroacetic acid (DCA) was developed for fabricating high $J_c$ REBCO film. DCA based-precursor solution was coated on $LaAlO_3$(001) substrate by dip coating method. Processing parameters such as oxygen partial pressure, water vapor, ramping rate and pyrolysis temperature were controlled in order to obtain a good epitaxial film. The film with thickness of 0.5 micrometer was obtained by single coating and no crack was observed at calcined films. Oxygen partial pressure was controlled in the range of $100{\sim}1,000$ ppm and conversion heat treatment was carried out at the temperature range of $705-765^{\circ}C$. A critical transition temperature ($T_c$) of 90 K and a critical transport current density ($J_c$) of $>0.5\;MA/cm^2$ (77 K and self-field) were obtained for the GdBCO film. It is thought that fluorine-free MOD solution using DCA is promising precursor solution for fabricating high quality REBCO films.

Effects of seed geometry on the crystal growth and the magnetic properties of single grain REBCO bulk superconductors

이휘주,박순동,전병혁,김찬중,이희균 한국초전도.저온공학회 2017 한국초전도저온공학회논문지 Vol.19 No.3

This study presents that the orientation and the geometry of seed affect on the growth behavior of melt processed single grain REBCO bulk superconductor and its magnetic properties. The effects of seed geometry have been investigated for thin 30mm x 30mm rectangular powder compacts. Single grain REBCO bulk superconductors have been grown successfully by a top seed melt growth method for 8-mm thick vertical thin REBCO slab. Asymmetric structures have been developed at the front surface and at the rear surface of the specimen. Higher magnetic properties have been obtained for the specimen that c-axis is normal to the specimen surface. The relationships between microstructure, grain growth and magnetic properties have been discussed