THE INFLUENCE OF MAGNETIC-FIELD ON CURRENT-VOLTAGE CHARACTERISTICS OFFINE-FILAMENT NBTI SUPERCONDUCTORS AND THE EFFECT OF A FILAMENT BREAK

The current-voltage characteristics of fine-filament composite wires f or Ac applications are exponential in a wide range of the transport cu rrents I and electric fields E. It is observed that the straight lines log E(I) measured at different external magnetic fields H intersect e ach other close to the single point extrapolated to the low-current an d field E region. This fact and some additional experiments allow us t o conclude that I-E characteristics of the fine-filament wires are, co ntrolled by strong defects at which the critical current value decreas es substantially. These defects are assumed to be due to breaks in the superconducting filaments. A simple model is proposed to describe the E(I, H) dependence for fine-filament superconductors.