Finite Element Analysis of the Energized ITER TF Coil in Test Conditions

The ITER magnet system comprises 18 superconducting Toroidal Field Coils (TFC) based on Nb₃Sn conductor supplied with the operational nominal current of 68 kA to produce a toroidal magnetic field of 5.2 T at the plasma major radius R = 6.2 m. A Magnet Cold Test Bench (MCTB) to test the TFC at 4 K up to a current value of 68 kA is under construction at ITER Organization (IO) site. The foreseen test conditions are substantially different from those corresponding to the 18-coil operation as the coils will be tested individually in horizontal position and supported at a few locations along the case. On the one hand, the magnetic field distribution produced by one single coil yields a different pattern of Lorentz forces. On the other hand, the absence of case wedging results in a reduced structural stiffness of the analyzed system. Finite element analysis work on this subject has been reported in the past for the TF Winding Pack (WP) after impregnation without undergoing the enclosure in the case, showing that the TF WP could be tested in safe conditions at a reduced energization of 15 kA (20% of the nominal current). This work considers currents up to the nominal 68 kA and the TF case which provides additional stiffness to the coil. Prior to the energization load, the coil is subject to gravity and cooled down to 4 K.