Electromagnetic evaluation of the collective behavior of 720 twisted strands for the TF model coil experiment

The TF model coil experiment is aimed at simulating the magnetic behavior o f the Toroidal Field system of ITER, This coil will, operate in de current mode. Even in these conditions, the theoretical critical currents of the ca ble, which should be the sum of the critical current of tile 720 supercondu cting strands, may not be reached. Tile intrinsically non-perfect current d istribution in the connection area can affect the conductor performances in the peak field region, only 1.2m away. This has a strong influence on the voltage-current characteristic and can generate a quench before the theoret ical critical current is reached, The theoretical critical current chart is calculated as a function of temperature and field. This calculation is bas ed on a precise characterization of the strand at different temperatures an d fields, coupled to quality assurance far each of the billets. A redistrib ution process is activated by the saturation of the overloaded strands lead ing to current transfer into underloaded strands[4]. The interstrand contac t resistance and the field pattern affect this process.