Non-uniformity of coated conductor tapes

Abstract

Non-uniformity of superconductor properties, e.g. a critical current reduction close to the edge of a coated conductor (CC) tape could degrade its performance in some power applications. Reliable characterization of such non-uniformity and understanding of its mechanism requires investigation of the character and causes of degradation. In this paper spatial distribution of critical current density across the width of a CC tape is studied. Three different experimental methods allowing estimation of the local current density were utilized for this purpose: (i) magnetic field mapping above the tape through which a DC current is flowing, (ii) measurement of the critical current of separate strips prepared by patterning of the CC tape, and (iii) magnetization measurements of the pieces cut from various positions within the tape width. Very good agreement between the results obtained by these methods was found, showing a reduction of the critical current density at the tape edges with respect to its centre. Moreover, structural investigation by scanning electron microscopy revealed a correlation between the morphology and the critical current density across the tape width. Insertion of such real non-uniform distribution of critical current density into AC loss calculation resulted in a dramatic improvement in the agreement with experimental results.

Spark-Discharge Plasma as a Method to Produce Low AC Loss Multifilamentary (RE)Ba2Cu3 O7 Coated Conductors

“…This is likely to have two main contributions: J c nonuniformities across the tape width [18], [19] or, in the case of the filamentary samples, magnetic coupling of filaments [20].…”

Potential and limits of numerical modelling for supporting the development of HTS devices

“…Several techniques can be used to extract this lateral dependence. The use of a position-dependent J c for AC loss calculations can often give a better agreement with experimental data [43,44]. A position-dependent J c can also be used to simulate the presence of defects [45,46].…”

Transport ac loss in a rectangular thin strip with power-law E(J) relation

“…(1)-(3) [5][6][7][8][9][10][11][12][13][14][15], which means that the CS model is basically valid for such tapes. However, this comparison between experimental and modeling results is somewhat ambiguous, since the relations between current density J and electrical field E in the actual HTS tapes and in the CS model are significantly different.…”

“…(4) have been calculated by Chen and Gu [20,21], using a numerical technique proposed by Brandt and developed for the transport case by Rhyner and Yazawa et al [22,23]. A scaling law has been derived in terms of vector potential, so that for any given value of n, the qði m Þ function calculated at fixed I c and f may be used for any http Physica C 508 (2015) [12][13][14][15][16] Contents lists available at ScienceDirect Physica C j o u r n a l h o m e p a g e : w w w . e l s e v i e r .…”