Evaluation of magnetic fields due to the ferromagnetic vacuum vessel and their influence on plasma discharge in tokamak devices

We studied characteristics of the magnetic fields due to a ferromagnetic vacuum vessel (F-W) experimentally and computationally to clarify whether plasma discharge is possible with the F-W in tokamak devices. We made three kinds of evaluations using the Hitachi tokamak HT-2, One was a discharge test with error field coil. The second was a numerical analysis of the magnetic field induced by a ferritic first wall. The third was a discharge test with the ferritic first wall. Consequently, we confirmed that a normal plasma discharge could be obtained with a ferritic first wall in the HT-2. The strength of the localized magnetic field induced by the F-W in the plasma region was smaller in tokamak devices with the size of the JFT-2M and ITER than in the HT-2, Therefore, the F-W should be applicable to tokamak devices. (C) 1999 Elsevier Science B.V. All rights reserved.