Estimation Of Critical Current Density Research Articles

Estimation of critical current density of bulk superconductor with artificial neural network

Estimation of critical current density of bulk superconductor with artificial neural network

Finite Element Method Based Estimation of Critical Current Density of NbTi

The purpose of this article is to estimate the magnetic field dependent critical current density scaling relation of NbTi used in a superconducting wire. The estimation problem is set using a finite element method based forward model solving the critical current of a wire in external magnetic fields. A sensitivity analysis is carried out to reveal the uncertainties in the process. It is shown that the methods provide accurate predictions of critical currents in a wire, but there are uncertainties related to the zero-field critical current density of the material.

Comparing the Effects of Nb, Pb, Y, and La Replacement on the Structural, Electrical, and Magnetic Characteristics of Bi-Based Superconductors

In this study, the effects of Pb, Nb, La, and Y replacements were investigated on Bi-based superconducting materials. In preparing the samples, we used a method called solid-state reaction method. The patterns of the X-ray diffraction of all samples indicated presence of Bi-2212 and Bi-2223 phases. The results obtained from XRD revealed that with increase of the melting point of substation elements, the Bi-2223 phase decreased while the Bi-2212 phase and impurity phases of samples grew. From the electrical resistivity measurements using the four-probe method, it was found that sample A with Pb and sample B with La replacements had the maximum and minimum critical temperatures of 111.4 and 81.6 K, respectively. Based on hysteresis loop (M–H) measurement using Bean’s model, estimation of critical current density (Jc) showed that sample A with Pb and sample B with La substitution had the maximum and minimum values respectively. These results may be due to the melting point of these elements with values of 888, 1512, 2315, and 2425 ∘C for PbO, Nb2O5, La2O3, and Y2O3, respectively. These elements were replaced by Bi2O3 with a melting point of 817 ∘ C. Further, the samples were prepared at the temperature of 845 ∘C. It seems at this temperature, these elements not only dissolve within the main matrix and participate in the formation of the Bi-2212 phase during the sintering process but they also participate in the development of the variety of the impurity phases as confirmed by XRD results.

Effect of distribution of powder size on estimation of critical current densities in polycrystalline Sr0.6K0.4Fe2As2 superconductors

The effect of distribution of powder size on the estimation of intra-grain critical current density was investigated for polycrystalline samples of Sr0.6K0.4Fe2As2 with and without addition of Ag 20wt.%. It turned out that the value of intra-grain critical current density calculated using the average of powder size Jcl is more overestimated than that calculated taking account of the distribution of powder size JclP as the distribution of powder size is widened, since the magnetic moment drastically increases due to the larger contribution from larger particles. From the distribution of powder size obtained by the microscopic observation using SEM, the factor of overestimation of Jcl/JclP is found to be larger than two in both samples. Moreover, the distribution of powder size in the Ag-added sample is found to be smaller than that of pure sample. Therefore, the factor of overestimation of Jcl is considered to be smaller in the Ag-added sample. It is recommended to take account of the distribution of powder size for precise estimation of intra-grain critical current density.

Contactless Estimation of Critical Current Density and Its Temperature Dependence Using Magnetic Measurements

Contactless Estimation of Critical Current Density and Its Temperature Dependence Using Magnetic Measurements A. Youssef, L. Banicova, Z. Svindrych and Z. Janůb,∗ Charles University in Prague, Faculty of Mathematics and Physics, 121 16 Prague 2, Czech Republic Institute of Physics of the AS CR, v.v.i., Na Slovance 2, 182 21 Prague, Czech Republic We have measured magnetic response of second-generation high temperature superconductor YBa2Cu3Ox wire and Nb thin film in perpendicular ac field as a function of temperature. We compare experimental complex ac susceptibility to the calculated susceptibility based on the model of Bean’s critical-state response in two-dimensional disk in perpendicular field. The harmonic analysis is needed for comparison between the model and the experimental data. We present a method of linking model and experimental susceptibility. Good agreement of experimental susceptibility with model susceptibility of 2D disk allows contactless estimation of critical depinning current density and its temperature dependence.

The effect of reversible flux motion on the estimation of critical current density in a thinsuperconductor using a third harmonic voltage method

A significant overestimation of the critical current densityJc is foundfor a measuring method of induced third harmonic voltage for thin superconductors of thickness lessthan 1 µm. This is speculated to be caused by a reversible motion of flux lines in a pinningpotential which reduces the nonlinear properties such as AC losses or the thirdharmonic voltage. It is known that the effect of reversible flux motion is prominentfor superconductors with a thickness comparable to or smaller than the pinningcorrelation length of the order of a sub-micrometre, the so-called Campbell’s ACpenetration depth. In this paper the effect of reversible flux motion on the estimation ofJc by this method is preliminarily investigated by using a simplified Campbell’s model for theforce–displacement characteristics of flux lines.

Superconductivity, X-ray photoemission and Raman scattering study of MgB 2 thin films

Highly c-axis oriented MgB 2 thin films with T c onset of 39.6 K were fabricated by magnesium diffusing into pulsed laser deposited boron precursors. Estimation of critical current density J c, using hysteresis loops and the Bean model, gave the value of 10 7 A/cm 2 (15 K, 0 T), which is one of the highest values ever reported. The X-ray photoemission spectra of the MgB 2 thin film revealed the binding energy of Mg 2p and B 1s are at 49.4 and 186.9 eV, respectively. The Raman spectra showed a typical broad band centered at 620 cm −1 with shoulders at 294, 410 and 730 cm −1 respectively. The dominant band at 620 cm −1 is interpreted as the first-order Raman response from the E 2g phonon of MgB 2 and the other three bands are properly originated from the phone density of states in MgB 2.

Superconductivity and x-ray photoemission study of MgB 2 thin films

Highly c-axis oriented MgB2 thin films with T-c(onset) of 39.6K were fabricated by magnesium diffusing into pulsed-laser-deposited boron precursors. The estimation of critical current density J(c), using hysteresis loops and the Bean model, has given the value of 10(7) A/cm(2) (15K, 0T), which is one of the highest values ever reported. The x-ray photoemission study of the MgB2 thin films has revealed that the binding energies of Mg 2p and B 1s are at 49.4 eV and 186.9 eV, which are close to those of metallic Mg and transition-metal diborides, respectively.

Noncontact estimation of critical current density and magnetic susceptibility in a ring-shaped high Tc superconductor

Abstract This paper describes the method of noncontact estimation of critical current density and magnetic susceptibility in a ring-shaped high T c superconductor. In this superconductor, a permanent current is induced by turning on and off an external magnetic field. The critical current density calcurated from the maximum value of the permanent current is adequately correlated with the critical current density and the susceptibility measured in the superconductor cut from the ring specimen.