Experimental and theoretical approach of current distributions and losses in superconducting composites for fusion magnets

In untwisted composites, azimuthal induced currents are responsible for magnetization and losses. In twisted composites extra coupling longitudinal currents are induced, owing to the solenoidal aspect of the filaments. A model is presented which takes into account the magnetization of both origin. Expressions are proposed as functions of the amplitude of the pulsed ex - ternal field. Experimental results are in good agreement. Critical densities for induced currents are given.