Critical Current in YBCO Coated Conductors in the
Presence of a Macroscopic Defect

Milan Polak, Paul N. Barnes, Pavol Mozola, and George A. Levin

Abstract— We have studied the effects of localized defects in the YBCO coated conductors on the critical current. The artificial defects were introduced into 4, 10 and 12 mm wide tapes as cuts of various lengths made either by laser ablation or mechanical means. Transport measurements were carried out in an external variable magnetic field to obtain the I-V characteristics of the damaged areas. The distribution of the magnetic field in the vicinity of the defects has been mapped as well. The reduction of the critical current by the defects, with and without an external DC magnetic field are discussed and compared with existing theories. A criterion for determining the critical current in the area containing a defect is suggested.

Index Terms— Coated Conductors, Defects, HTS, YBCO

Manuscript received August 19, 2008. This work was supported in part by the Air Force Research Laboratory and Office of Scientific Research, grant FA8655-07-1-3005.
M. Polak and P. Mozola are with the Institute of Electrical Engineering, Slovak Academy of Sciences, SK-84104 Bratislava, Slovakia (e-mail: milan.polak@savba.sk).
P. N. Barnes and G. A. Levin are with the Air Force Research Laboratory, WPAFB, OH 45433 USA. (e-mail: paul.barnes@wpafb.af.mil).

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