INFLUENCE OF IRRADIATION-INDUCED CORRELATED AND RANDOM DISORDER ON FLUX-PINNING IN BULK YBCO MELT-TEXTURED SAMPLES

YBCO melt textured samples were studied after Au ion irradiation of tw o opposite surface layers of the samples and after proton irradiation. The scaling behavior of the pinning force was studied in order to get information about mechanisms responsible for pinning in the studied s amples. Correlated disorder introduced by surface ion irradiation is e ffective at high reduced temperatures and leads to the occurrence of a kink in the irreversibility line and to, the shift of this line towar d higher fields and temperatures. Enhancement of critical current dens ity, increasing with temperature and field, was observed. Random disor der due to proton irradiation does not change the irreversibility line and only provides critical current enhancement den easing with temper ature and field.