Spiral superconducting Nb-Ti filaments: electric field and critical current

As a first step to a better understanding of the voltage-current characteristics of fine filament multifi lamentary composite superconductors, the electric field and critical current along a single spiral-shaped fi lament were studied. When the spiral superconducting filament was carrying constant current and placed in a magnetic field, the local critical current and electric field vary due to the change of the angle between the magnetic field and filament axis. A theory is presented which enables us to calculate the mean and local values of the electric field and critical current of spiral samples for arbitrary orientation between the magnetic field and spiral axis. The presented experimental results are in good agreement with this theory.