• Progress in Superconductivity
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• 제13권1호
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• pp.28-33
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• 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.

• Progress in Superconductivity
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• 제11권2호
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• pp.128-134
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• 2010

The magnetic flux profiles in SmBCO and YBCO coated conductors(CC) in the presence of the external field were comparatively investigated by magneto-optic image and scanning hall probe measurements. The current distributions calculated by using the inversion method from measured field profiles show that the decrease of current densities near the edges of SmBCO CC is more significant than those of YBCO CC. Through the comparison of the numerical analysis based on Kim's critical state model and the Brandt and Indenbom's solution, we found that this feature is related to their different field dependant properties of the critical current densities.

• Progress in Superconductivity
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• 제13권3호
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• pp.169-177
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• 2012

Distribution of the local properties in GdBCO and YBCO coated conductors was investigated using Low-temperature Scanning Laser and Hall Probe Microscopy (LTSLHPM). We prepared GdBCO and YBCO coated conductors to study the spatial distribution of the current density in a single bridge. Inhomogeneity of the ${T_c}^{max}$ in the bridge was analyzed from experimental results of Scanning Laser Microscopy (SLM) near the superconducting transition. The local transport and screening current in the bridge were also investigated using Scanning Hall Probe Microscopy (SHPM). A series of line scans of SLM of the GdBCO and YBCO sample showed that lines with more inhomogeneous distributions of ${\delta}V$ had more inhomogeneous distributions of ${T_c}^{max}$. The defect of the superconducting layer of the GdBCO sample caused by damage to the substrate affected the current flow. And we could analyze the redistribution of the current density using SLM and SHPM.

• Progress in Superconductivity
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• 제8권2호
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• pp.169-174
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• 2007

We measured the field profiles, H(x)'s of coated conductors by using scanning Hall probe method when various magnetic fields, $H{_\alpha}'s$ or currents, I's were applied. From the measured field profiles, we calculated the current profiles, J(x)'s by the inversion method. The calculated J(x)'s of coated conductors show some different properties from the standard critical state model. $J{_c}'s$ are inhomogeneous varying with the positions and are not constant when $H_{\alpha}$ or I changes. And when I decreases the features of current reversion are remarkably different from the model.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2009년도 Korea Superconductivity Society Meeting 2009
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• pp.83-83
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• 2009

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2007년도 High Temperature Superconductivity Vol.XVII
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• pp.33-33
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• 2007

• 한국초전도ㆍ저온공학회논문지
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• 제9권3호
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• pp.13-15
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• 2007

We employed home-made position marking module in the scanning Hall probe system. The module is composed of two coils of which gap, a, between wires in a coil is $500{\mu}m$. We appiled 10-35mA of current with 15Hz in the coils and recorded ac corresponding magnetic field signal with respect to measuring time while we measured DC field profiles produced due to superconducting film in a perpendicular magnetic field. We calibrate the position, x, of coils using the measuring time and location of the coils in the holder. The error range was about ${\pm}0.1mm$. We test the module as we applied current of 100A and filed of 1kG in the superconducting tape. It was confirmed that there was no interference between superconducting tape and marking coils.

• Progress in Superconductivity
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• 제13권1호
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• pp.34-39
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• 2011

본 연구를 통해서 초전도 선재 시료의 국소적인 영역에 대한 전류 밀도의 공간적인 분포를 시료의 손상 없는 비파괴적인 방법으로 LTSHPM을 통해서 1차원 2차원으로 형상화해 보았다. 그 결과 외부자기장에 의한 차폐전류의 흐름을 분석할 수 있었다. 또한 MPMS에서 외부자기장에 따른 자기모멘트를 측정한 결과와 LTSHPM을 통해 전류 밀도 분포를 분석한 결과를 비교해 볼 때 외부자기장에 의한 반자성의 크기와 자기모멘트로 인해 생기는 차폐전류가 100 Oe에서 최댓값을 가지는 일치하는 결과를 얻을 수 있었다. 그리고 세 가지의 평행한 브릿지에 흐르는 차폐전류를 2차원적으로 분석해 본 결과 시료 전체적으로 가장 바깥쪽으로 차폐전류가 흐르는 공통점을 확인해 볼 수 있었다.

• 한국초전도ㆍ저온공학회논문지
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• 제19권1호
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• pp.26-29
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• 2017

We studied the distribution of the current density and its magnetic-field dependence in GdBCO coated conductors with AC bias currents using low temperature scanning Hall probe microscopy. We selectively measured magnetic field profiles from AC signal obtained by Lock-in technique and calculated current distributions by inversion calculation. In order to confirm the AC measurement results, we applied DC current corresponding to RMS value of AC current and compared distribution of AC and DC transport current. We carried out the same measurements at various external DC magnetic fields, and investigated field dependence of AC current distribution. We notice that the AC current distribution unaffected by external magnetic fields and preserved their own path on the contrary to DC current.

• 한국초전도ㆍ저온공학회논문지
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• 제9권3호
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• pp.1-4
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• 2007

The current profiles in a coated conductor with transport current were calculated using an iterative inversion method from the data of the magnetic flux density profiles measured. The applied current was increased from 0 to 60 A by 10A step and decreased down to -60A by 20A step. The magnetic flux profiles were measured at a distance of 400 mm above the surface of the coated conductor using a scanning hall probe method. The current profiles calculated were very different from the Bean model: current density profile is not a constant in the critical region. However the aspect of the change of the current and magnetic flux density profiles in the case of decreasing applied current are similar to the theoretical calculations in Brandt's paper.