• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
• /
• 2002.02a
• /
• pp.277-280
• /
• 2002

It is well known that the critical current of a HTS tape has anisotropic characteristic in magnetic field. We are interested in critical current density distribution of a HTS tape. We assumed the experimentally obtained Ic-B curves do represent the local properties of HTS tapes and calculated the critical current density distribution of HTS tapes using numerical method. Also we predicted the critical current of the tapes.

• Progress in Superconductivity
• /
• v.12 no.1
• /
• pp.17-22
• /
• 2010

Distribution of local critical temperature and current density in $YBa_2Cu_3O_{7-\delta}$ (YBCO) coated conductors was analyzed using a Low-temperature Scanning Laser Microscopy (LTSLM). We prepared YBCO coated conductors of various bridge types to study the spatial distribution of critical temperature and current density in single and multi bridges. An LTSLM system was modified for a detailed two-dimensional scan without shifting of the sample. We observed a spatial distribution of the critical temperature from the bolometric response, which arises from a focused laser beam at the sample near the superconducting transition. Also we studied the relation between the critical temperature and the current density.

• Progress in Superconductivity
• /
• v.13 no.1
• /
• pp.28-33
• /
• 2011

Distribution of the local critical temperature and current density in YBCO coated conductors were analyzed using Low-temperature Scanning Laser and Hall Probe Microscopy (LTSLHPM). We prepared YBCO coated conductors of various bridge types to study the spatial distribution of the critical temperature and the current density in single and multi bridges. LTSLHPM system was modified for detailed linescan or two-dimensional scan both scanning laser and scanning Hall probe method simultaneously. We analyzed the local critical temperature of single and multi bridges from series of several linescans of scanning laser microscopy. We also investigated local current density and hysteresis curve of single bridge from experimental results of scanning Hall probe microscopy.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09b
• /
• pp.1243-1244
• /
• 2006

Five kinds of double stacked 385 (55 x7) filamentary Bi2212/Ag round wires and 55 filamentary tapes with different Ag ratios (silver area/superconductor area) have been fabricated via PIT method, and the effects of Ag ratio and processing factors on critical current density were studied. The effects of the maximum temperature and average filament diameter on critical current density were also studied. The wire of 0.74 mm diameter having Ag ratio 3.7 showed critical current density of $2,218\;A/mm^2$ at 4.2 K, 0 T.

• Transactions of Materials Processing
• /
• v.29 no.1
• /
• pp.37-43
• /
• 2020

Increasing the critical current density of superconducting wire is one of the difficult challenges in the field of superconductivity. It is well known that the higher volume fraction of uniformly dispersed α-Ti is able to enhance the critical current density of superconducting material NbTi because α-Ti serves as a flux pinning center. The volume fraction of α-Ti highly depends on the grain size of NbTi because α-Ti precipitates at the grain boundaries or triple points. For this purpose, we investigated the effect of initial microstructures of NbTi obtained from hot rolling in various temperature conditions on the critical current density. In addition, subsequent heat treatment was assigned to precipitate α-Ti and groove rolling/cold drawing was adopted to produce a wire with a diameter of about 1.0 mm. It was observed that the band structure was formed after hot rolling at 500~600℃. It was also found that the volume fraction of α-Ti after hot rolling at 500~600℃ was higher and it led to the highest critical current density.

• Transactions on Electrical and Electronic Materials
• /
• v.1 no.1
• /
• pp.12-16
• /
• 2000

In this paper, we analyze self field effects of Bi-2223 tape-stacked cable assuming constant current density in the cross section of stacked cable. Generally, the critical current of Bi-2223 tape-stacked-cable in much less than the total summation of critical currents of each tape, which is mainly due to the self magnetic fields of the cable itself. Therefore, to predict the critical current of Bi-2223 tape-stacked-cable, we needs to analyze the self filed effects on the stacked cable as well as critical current density data(J$\_$C/) of one tape. To make it more complex, the critical current degradation of Bi-2223 tape is an-isotropic; the critical current is lower in the normal magnetic field(to the tape surface) than in the parallel field. In the paper, a novel approach to predict the critical current of a Bi-2223 tape-stacked-cable from a J$\_$C/-B curve of one tape is presented with the assumption of constant current density across the stacked cable, The approach basically includes the load analysis of the stacked tapes, and its usefulness is confirmed by the experimental data.

• Progress in Superconductivity and Cryogenics
• /
• v.12 no.3
• /
• pp.16-20
• /
• 2010

For large scale power applications of HTS conductor, it is getting more important to have a stacked HTS coated conductor with low loss and large current capacity. But it was not easy to measure some electric properties. Stabilizer free YBCO CC for striated/ stacked conductors is easily burned out during the measurement of the critical current density because it has no stabilizer and it is difficult to set-up the current lead and voltage taps because it has many pieces of YBCO CC in a conductor. Instead of direct measuring the critical current of a stacked HTS coated conductor, indirect estimation from measuring a magnetization loss of HTS coated conductor could be useful for practical estimation of the critical current. The magnetization loss of a superconductor is supposed to be affected by a full penetrating magnetic field, and it tends to show an inflection point at the full penetrating magnetic field when we generate the graph of magnetization loss vs. external magnetic field. The full penetrating magnetic field depends on the shape of the conductor and its critical current density, so we can estimate the effective critical current density from measuring the magnetization loss. In this paper, to prove the effectiveness of this indirect estimation of the critical current, we prepared several different kinds of YBCO CC(coated conductor) including a stacked conductor short samples and measured the magnetization losses and the critical currents of each sample by using linked pick up coils and direct voltage measurement with transport current respectively.

• Progress in Superconductivity and Cryogenics
• /
• v.23 no.4
• /
• pp.10-13
• /
• 2021

Recently, cable conductors composed of numerous coated conductors have been developed to transport huge current for large-scale applications, for example accelerators and fusion reactors. Various cable conductors such as CORC (Conductor on round core), Roebel Cable, and TSTC (Twisted stacked tape cable) have been designed and tested to apply for large-scale applications. But, these cable conductors cannot improve the engineering critical current density (J_e) because they are made by simple stacking of coated conductors. In this study, multi-HTS (High temperature superconductor) layers on one substrate (MHOS) wire was fabricated to increase the engineering critical current density by using the exfoliation of superconducting layer from substrate and silver diffusion bonding method. By the repetition of these processes, the 10 m long 6-layer MHOS conductor was successfully fabricated without any intermediate layers like buffer or solder. 6-layer MHOS conductor exhibited a high critical current of 2,460A/12mm-w. and high engineering critical current density of 1,367A/mm² at liquid nitrogen temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.04a
• /
• pp.37-40
• /
• 2002

Superconductor wire fabricated by electrophoresis showed its critical current density depended on parameters such as applied voltage and deposition time. Substrate and suspension solutions. and its properties are also important parameters. When same optimal parameter and condition was used, deposition density of superconductor film affect directly its critical current density. In this study, therefore, electrophoretic deposition technique was utilized for a densification of YBCO superconducting wire, and researches on electrophoretic suspension solutions and additive were experimentally performed for an improvement of the critical current density of fabricated electrophoretically superconducting wire. The samples fabricated in the solution with the additive, 8 vol.% of 1% PEG(1000), showed the highest critical current density.

• Proceedings of the KIEE Conference
• /
• 1997.07a
• /
• pp.260-263
• /
• 1997

In this paper, we describe the mechanical strain effects on the critical current density of HTS (BSCCO) pancake-type-magnet. Firstly the strain of pancake coil is calculated in terms of coil length, which is also a function of angle, and then the critical current density degradation due to strain is calculated along the coil. We assumed that the critical current density degradation pattern is same with that of $Nb_{3}Sn$. We also modelled the effects of magnetic field on the critical curent degradation, and the results are compared with those with null magnetic field.