Effective thermal conductivity of the conductor insulation of the ITER toroidal field model coil at operation temperature

During current transients in the toroidal field model coil (TFMC), the radial plates carry eddy currents that generate Joule heat. The heat sink is the forced flow helium cooling of the conductor. Vice versa, during accidents, the radial plates act as a heat sink during the heat up of the conductor. In both cases, the time constant of heat transfer is given by the thermal conductivity of the insulation of the conductor. The code system MAGS (magnet system) is used to recalculate fast discharge experiments of the TFMC at the TOSKA facility. The model takes into account the transient magnetic field, the current in the conductor circuit, in the radial plates and coil case, the ac-losses in the conductor and the helium flow. The results clearly indicate that the power distribution in the radial plate should be taken into account and the thermal conductivity of the insulation is considerably lower than assumed up to now.