Correntes críticas e comportamento dinâmico dos vórtices em fitas supercondutoras do tipo II com arranjos conformes de centros de aprisionamento

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Test results of a superconducting fault current limiter using YBCO coated conductor

A single-phase superconducting fault current limiter (SFCL) using a 0.9 m length of YBCO coated conductor (CC) tape was tested in 220 V-60 Hz line for fault current up to 1 kA, operating in 77 K. In this work are presented the IN experimental curves measured under DC and AC currents for the electrical characterization of the CC tape in order to design a low voltage current limiter. The experimental setup is described and the test results are presented for a unit conducting a steady nominal AC current of 50 A and also during the fault time (I to 5 cycles.) the performance of the CC-based SFCL providing the limiting resistance developed in the whole tape length after few milliseconds of the beginning of the fault was analyzed.

Electrical and Superconducting Properties in Lap Joints for YBCO Tapes

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Anelastic characterization and superconducting properties of RuSr2GdCu2O8+delta

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Vortices in a mesoscopic superconducting disk of variable thickness

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Vortex-Antivortex Dynamics in a Mesoscopic Superconducting Prism with a Centered Antidot

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Superconducting boundary conditions for mesoscopic circular samples

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Magnetic response of superconducting mesoscopic-size YBCO powder

In this work it is reported the magnetic behavior of submicron and mesoscopic-size superconducting YBCO powders, prepared by a modified polymeric precursors method. The grain size and microstructure were analyzed using scanning electron microscopy ( SEM). Measurements of magnetization and AC-susceptibility as a function of temperature were performed with a quantum design SQUID magnetometer. Our results indicated significant differences on the magnetic propreties, in connection with the calcination temperature and the pressure used to pelletize the samples. This contribution is part of an effort to study vortex dynamics and magnetic properties of submicron and mesoscopic-size superconducting samples. (C) 2008 Elsevier B. V. All rights reserved.

Vortex dynamics in mesoscopic superconducting square of variable surface

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Heat-treatment effects on the magnetic response of superconducting mesoscopic samples

The use of chemical methods in the synthesis of high-quality and small-size polycrystalline samples has been increased in recent years. In this work, a chemical route based on an aqueous precursor solution of metals followed by the addition of a water-soluble polymer formed by ethylenediaminetetraacetic acid (EDTA) and ethylene glycol (EG) was tested to produce superconducting mesoscopic YBa(2)Cu(3)O(7-gamma) samples. Different conditions of heat treatments and the effects of argon and oxygen atmospheres during the calcination steps were traced using X-ray diffraction (XRD), scanning electron microscopy (SEM) and magnetic measurements. (C) 2008 Elsevier B. V. All rights reserved.

Superconducting state in a mesoscopic segment ring

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Temperature-dependent vortex matter in a superconducting mesoscopic circular sector

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Oxygen diffusion in superconducting oxides

Since the discovery of high-temperature superconductivity of cuprate oxides, it has been clear that it is strongly affected by the oxygen content, which is also a crucial factor to determine other physical properties of high T-c superconductors. Non-stoichiometric (interstitial) oxygen strongly influences the physical properties of various superconducting oxides, in particular by creating conducting holes. It is now ascertained that the amount of holes injected depends not only on the content of interstitial oxygen, but also on its ordering. Rearrangement of the oxygen ordering may occur even below room temperature due to the unusual high mobility of these atoms. This way, mechanical spectroscopy is one of the most adequate techniques for the study of the mobility (diffusion) of oxygen atoms. This technique allows the determination of the jump frequency of an atomic species precisely, regardless of the model or the different possible types of jumps. In order to evaluate the mobility and the effect of oxygen content on these oxides, ceramic samples we prepared and submitted to several oxygen removal cycles alternately with mechanical relaxation measurements. As for SBCO, it was assumed that the peak was due to O(1)-O(5) jumps of oxygen atoms at the chain terminals or in chain fragments in the orthorhombic phase. In the case of BSCCO, the results showed complex anelastic relaxation structures, which were attributed to interstitial oxygen atom jumps between two adjacent CuO planes.

Vortices in a mesoscopic superconducting circular sector

In the present paper we develop an algorithm to solve the time dependent Ginzburg-Landau equations, by using the link variables technique, for circular geometries. In addition, we evaluate the Helmholtz and Gibbs free energy, the magnetization, and the number of vortices. This algorithm is applied to a circular sector. We evaluate the superconduting-normal magnetic field transition, the magnetization, and the superconducting density. Our results point out that, as we reduce the superconducting area, the nucleation field increases. Nevertheless, as the angular width of the circular sector goes to small values the asymptotic behavior is independent of the sample area. We also show that the value of the first nucleation field is approximately the same independently of the form of the circular sector. Furthermore, we study the nucleation of giant and multivortex states for the different shapes of the present geometry.

Vortex-antivortex annihilation dynamics in a square mesoscopic superconducting cylinder

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)