  Analysis of the resistive transition of a polycristalline YBCO specimen
produced by an a.c. magnetic field, reveals the presence of a large conductance
noise signal which is repetitive over subsequent magnetization cycles. It is
shown that the noise arises from avalanche effects produced by the simultaneous
resistive transition of large groups of weak links. Owing to its repeatability,
the noise signal may be considered a sort of signature of the weak links
critical current distribution, making it an interesting new tool for the study
of high Tc ceramic superconductors, as reported measurements of noise
hysteresis show.
