SELF-FIELD EFFECTS ON CRITICAL-CURRENT VALUES IN TL-1223 TAPES

We have measured the properties of a large number of Tl-1223 tapes as part of a programme to optimise the fabrication procedures. During thi s work we have noticed that the highest I-c values are not proportiona lly dependent on the cross-sectional geometry of the tapes. There seem s to be a limiting I-c value of around 10-13 A in our samples (and tho se of many other groups). We have performed a series of experiments on self-field effects in Tl-1223 tapes and compared the results with cal culated field distributions in tape-shaped conductors in different con figurations. We conclude that the I-c are self-field limited in these tapes when the currents being carried are around 10 A.