ANALYSIS OF ERROR FIELD DUE TO FERRITIC STEEL IN THE ADVANCED MATERIAL TESTING PROGRAM OF JFT-2M

The reduction of ripple due to the use of a ferritic steel is studied computationally for two types of vacuum vessel (VV): one is made of no nmagnetic material with. a ferritic section, and the other is made of ferritic steel. The appropriate setting of the ferritic section in the nonmagnetic material VV results in a ripple reduction in the whole pl asma region of the low held side and the ripple amplitude can be reduc ed by a factor of 3: the ripple amplitude is reduced from 1.8% to 0.6% on the plasma boundary. The ripple amplitude in the case of the ferri tic VV with the realistic horizontal port is comparable with that in t he case of the nonmagnetic VV with the ferritic section. (C) 1998 Else vier Science B.V. All rights reserved.