A STATISTICAL TECHNIQUE FOR THE INVESTIGATION OF WEAK POINTS AND DEGRADATION OF HIGH-TEMPERATURE SUPERCONDUCTOR TAPES

Recent technological developments in manufacturing high-temperature su perconductor (HTSC) tapes have improved their mechanical and electrica l performances considerably. Now, a near future when HTSC cables will become a reality can finally be forecast. This brings about the need f or work in the field of quality control and diagnostics of HTSC tapes. A new methodology for the analysis of the behaviour of tapes aged und er different kinds of mechanical stresses is presented in this paper. The methodology is based on a probabilistic approach, where the two-pa rameter Weibull function is used to fit the cumulative and density pro bability distributions obtained from experimental V-I characteristics by numerical-analytical differentiation. Experimental results relevant to both long-term (aging) and short-term tests performed on 2223-BSCC O tapes are presented and discussed. It is shown that the time behavio ur of Weibull function parameters provides useful information on the l evel of aging and on the kind of damage occurring to the tapes. In par ticular, the comparison between the results obtained from long-term an d short-term tests, as well as from different types of mechanical stre sses, points out that the shape of probability distributions constitut es a valuable diagnostic tool to distinguish between local or overall degradation and helps in identifying damage location.