Critical current density and trapped field in HTS with asymmetric magnetization loops

Applications of the extended critical state model are considered. The trapped magnetic field, the penetration field and the field dependence of the critical current density are analysed. The critical current density and the trapped field in superconducting grains depend on the grain size. Asymmetry of the hysteresis curves relative to the M = 0 axis is related to the scale of the current circulation.Comment: 5 pages, 4 figures, presented in the 9th International Workshop on Processing and Applications of Superconducting (RE)BCO Large Grain Materials (PASREG 2015

Magnetic flux trapping in porous superconductors

The magnetization of superconducting samples is influenced by their porosity. In addition to structural modifications and improved cooling, the presence of pores also plays a role in trapping magnetic flux. Pores have an impact on the irreversibility field, the full penetration field, and the remnant magnetization. Generally, as porosity increases, these parameters tend to decrease. However, in the case of mesoscopic samples or samples with low critical current densities, increased porosity can actually enhance the trapping of magnetic flux.Comment: 9 pages, 3 figure

Computation of current-voltage characteristics of weak links

Simplified model for current-voltage characteristics of weak links is suggested. It is based on approach which considers Andreev reflections as responsible for the dissipative current through the metallic Josephson junction. The model allows to calculate current-voltage characteristics of weak links (superconductor - normal metal - superconductor junctions, microbridges, superconducting nanowires) for different thicknesses of the normal layer at different temperatures. The current-voltage characteristics of tin microbridges at different temperatures were computed.Comment: 11 pages, 5 figure

Microstructural Parameters for Modelling of Superconducting Foams

Superconducting YBa2Cu3Oy (YBCO) foams were prepared using commercial open-cell, polyurethane foams as starting material to form ceramic Y2BaCuO5 foams which are then converted into superconducting YBCO by using the infiltration growth process. For modelling the superconducting and mechanical properties of the foam samples, a Kelvin-type cell may be employed as a first approach as reported in the literature for pure polyurethane foams. The results of a first modelling attempt in this direction are presented concerning an estimation of the possible trapped fields (TFs) and are compared to experimental results at 77 K. This simple modelling revealed already useful information concerning the best suited foam structure to realize large TF values, but it also became obvious that for various other parameters like magnetostriction, mechanical strength, percolative current flow and the details of the TF distribution, a refined model of a superconducting foam sample incorporating the real sample structure must be considered. Thus, a proper description of the specific microstructure of the superconducting YBCO foams is required. To obtain a set of reliable data, YBCO foam samples were investigated using optical microscopy, scanning electron microscopy and electron backscatter diffraction (EBSD). A variety of parameters including the size and shape of the cells and windows, the length and shape of the foam struts or ligaments and the respective intersection angles were determined to better describe the real foam structure. The investigation of the foam microstructures revealed not only the differences to the original polymer foams used as base material, but also provided further insights to the infiltration growth process via the large amount of internal surface in a foam sample

Анализ петель намагниченности сверхпроводников

The critical state model and the extended critical state model are described to analyse a magnetization hysteresis and to find superconductor parameters. We discuss how geometric sizes and form influence on magnetization hysteresis, critical current and trapped fluxОписано использование модели критического состояния и расширенной модели критического состояния для определения параметров сверхпроводников из измеренных петель намагниченности. Обсуждается влияние геометрических размеров и формы образцов на вид петель намагниченности, критический ток и замороженное магнитное пол

Анализ петель намагниченности сверхпроводников

The critical state model and the extended critical state model are described to analyse a magnetization hysteresis and to find superconductor parameters. We discuss how geometric sizes and form influence on magnetization hysteresis, critical current and trapped fluxОписано использование модели критического состояния и расширенной модели критического состояния для определения параметров сверхпроводников из измеренных петель намагниченности. Обсуждается влияние геометрических размеров и формы образцов на вид петель намагниченности, критический ток и замороженное магнитное пол