TAILORED DEFECTS IN HTSC - WHAT CAN WE LEARN FROM SWIFT HEAVY-ION IRRADIATION

Since the discovery of superconductivity above liquid nitrogen tempera ture in copper oxide based compounds many experiments have been perfor med on the one hand to study their mixed state properties and on the o ther hand to check their technological applicability. Due to their wel l defined cylindrical shape latent particle tracks (also known as colu mnar defects) are a powerful tool to investigate the mixed state in hi gh temperature superconductors (HTSC) as they provide optimized pinnin g centers. Therefore in this paper we will present experiments perform ed with HTSC samples (epitaxial thin films on SrTiO3 substrates, singl e crystals and technical tapes) containing columnar defects. We will o utline the influence of these linear defects on the resistive phase tr ansition and on transport I-V curves of YBa2Cu3O7-delta (123) thin fil ms. All HTSC known up to now exhibit a pronounced structure-related an isotropy. Hence we present magnetic and transport measurements concern ing the angular dependence of the critical current in various irradiat ed HTSC compounds. Furthermore experiments with technical tapes of (Bi Pb)2Sr2Ca2Cu3O10 (Bi2223) will be shown giving an overview of problems concerning technological applications. Finally in irradiated and noni rradiated Bi2Sr2CaCu2O8 (Bi2212) single crystals the flux line lattice is visualized via the high resolution Bitter decoration technique.