Effects of ferromagnetic materials on plasma control

Oyama, Naoyuki; Sato, Masayasu; Shinohara, Koji

Reduced activation ferritc/martensitic steel has been considered as a candidate of the structural material for DEMO reactor. Since effects of its strong magnetism on plasma production, plasma control and compatibility with high performance plasmas have been concerned, AMTEX project in JFT-2M demonstrates that the toroidal field (TF) ripple can be reduced by the ferritc steel tiles (FSTs) and there is no bad effect on the compatibility with high performance plasmas. Based on these results, the FSTs have been installed in JT-60U in order to improve the plasma performance through the reduction of the TF ripple. Then, it is confirmed that the effect of the error field due to the FSTs can be corrected so as to control the plasma. Although these experimental results indicate that the effect of the FSTs on plasma control seems to be small, the effect of the ferromagnetic materials inside the test blanket module for ITER on the plasma confinement has recently been concerned.