Self-field ac loss of Bi-2223 superconducting tapes

The powder-in-tube route for fabricating long lengths of multifilament Ag-sheathed Bi-2223 tape can be used to manufacture tapes with a variety of filamentary configurations. The design of the filament array within a tape will influence the electrical properties including the ac loss which becomes a significant consideration when designing a closed cooling system. The effect of periodically arranged filaments on the transport ac losses of Bi-2223 tapes has been investigated and the results compared with the Norris equations.

Section: Resultscontrasting

confidence: 60%

Transport ac losses of multifilament Ag-sheathed Bi-2223 tapes with periodically arranged filaments in the configuration

Darmann¹,

Zhao²,

McCaughey³

et al. 1998

“…In addition, LaAlO 3 single-crystal cylinders for dielectric resonator applications were covered by PLD with epitaxial YBCO films on both opposite cube-indexed (100) faces. Planar dc sputtering at high oxygen pressure from a stoichiometric target was used to cover 2 in LaAlO 3 wafers with (350-450) nm thick YBCO films on one or both sides [20,21].…”

Section: Methodsmentioning

confidence: 99%

Microstructure and microwave surface resistance of typical YBaCuO thin films on sapphire and LaAlO₃

Kästner

Schäfer

Senz

et al. 1999

Epitaxial c-oriented YBCO films laser deposited onto 3 in diameter CeO 2-buffered sapphire wafers and LaAlO 3 cylinders as well as sputter deposited onto 2 in diameter LaAlO 3 wafers were characterized by integral and spatially resolved measurements of the critical current density j c and the microwave surface resistance R s , by microstructure investigations using optical and electron microscopy and by x-ray diffraction. Epitaxial misorientations of in-plane-rotated as well as of a-axis-oriented grains were found in amounts up to 10%. The in-plane rotation seriously degraded R s while the a orientation mainly lowered j c. Moreover, a degradation of R s and of the microwave power handling could be clearly correlated with the density of microcracks occasionally found in YBCO films on sapphire. Inhomogeneities like a-axis-oriented grains were observed to 'disperse' microcracks, probably in favour of the electrical properties. The impact of further microstructure imperfections on R s , in particular of the typical twin lamellae and their domains, is discussed in view of findings from transmission electron microscopy.

“…When the experimental conditions allow us to neglect the self-field magnetic loss, P mag , with respect to the resistive loss, P res , the voltage measured on the wire in AC conditions should follow the dependence (7) derived originally for DC transport. The same conclusion has been tacitly used in several experimental works investigating the current-voltage curves in AC [8,9] and nicely documented in [10]. The experimental data of the latter work could be taken as the experimental confirmation of the validity of the expression (6) in the description of the AC current-voltage curve.…”

Section: A Model For the Calculation Of Resistive Ac Lossmentioning

confidence: 56%

Resistive losses in a high-T_cwire carrying AC current larger thanI_c

Gömöry

Janiková

Šouc

2002

A procedure that allows the calculation of the resistive AC loss in a multifilamentary superconducting wire carrying AC transport current was developed. This loss mechanism, detected by the appearance of a finite drop of electrical potential along the wire, is significant when considering transport currents with amplitudes that exceed the critical current of the wire. The physical model behind our calculation for a common wire, that contains superconducting filaments in a metallic matrix, is the simple parallel combination of two elements: the superconductor standing for the properties of all the filaments, and the normal resistor representing the matrix. The total current carried by two parallel conducting paths is easily calculated for any imposed potential drop. But the inverse task-calculation of the potential drop that would force a defined current to be transported-requires us to resolve a nonlinear equation. We show how it is possible to evaluate the resistive loss by a procedure that needs to perform the root-finding operation in one point of the cycle only. The numerical integration is still necessary, but now it is easily performed because the integrand is explicitly defined. The procedure was successfully tested by comparison with experimental data.