DINA analysis on effect of vertical position control on vertical force during VDE

Miyamoto, Seiji; Sugihara, Masayoshi*; Shinya, Kichiro*; Nakamura, Yukiharu*; Toshimitsu, Shinichi; Sugie, Tatsuo; Kusama, Yoshinori; Yoshino, Ryuji

When Plasma Control System (PCS) generates wrong signal to the PF coils and in-vessel vertical stabilization (VS) coils, it could be happen that the vertical force somewhat larger than presently specified could be generated. Example is that though plasma moves downward, but PCS erroneously recognizes it is moving upward. Then PF coils start to generate the field pattern that tends to push plasma further downward and resultantly the force could be larger than the present specification, in which it is evaluated with the assumption that control system (PF coils) does nothing (i.e., short-circuited.) In fact, in the existing machines, this is the worst case. The DINA code is used to analyze the vertical force, which has been updated to incorporate the recent design change of the vacuum vessel and in-vessel VS coils. In the presentation, analysis of VS effect on the vertical force is discussed using the updated DINA code.