Operational flexibility of CS-less tokamak power reactor

CSコイルのないトカマク炉の運転シナリオ

西尾 敏

Nishio, Satoshi

CSコイルを排除したトカマクプラズマの平衡配位はその断面形状、特に三角度に制限が課せられることが指摘されている。しかしながら三角度の決定因子はポロイダルコイルの位置の他にプラズマの電流分布と楕円度も重要なパラメータである。CSコイルを排除して、三角度,電流分布及び楕円度の三者間の定量的関係が詳細な平衡計算によって示されている。そこでは、著しい性能低下を招かない程度の楕円度(2以上は確保)の範囲及び実験の裏付けのある電流分布(0.5程度の規格化内部インダクタンス)の範囲内で必要な三角度は確保されている。

The CS coil system is an obstacle to a low cost construction. On the other hand, an operational flexibility (or capability) of CS-less tokamaks is restricted somewhat. This somewhat should be cared about. To be acceptable or not. To be compensatable or not. That is question.Even though the CS coil system is discarded from a tokamak device, plasma initiation and succeeding current ramp up are not any longer a critical issue of possible or impossible. The concerns will be shifted to how skillfully or how fast issues. More important issue is a plasma equilibrium forming. It is difficult to form an elongated plasma shape with high triagularity for CS-less poloidal field (PF) coils arrangement. Because there is no coil to push in the plasma column in a torus inner region. Focusing on the plasma shape being with reference to a plasma internal inductance, the operational parameter region is illustrated in elongation-triagularity-internal inductance space. Simultaneously and furthermore, allowable plasma elongation is discussed in terms of passive shell positioning, stability margin and plasma aspect ratio. Maximum achievable and minimum required triagularity are discussed.