Operational flexibility of CS-less tokamak power reactor

Nishio, Satoshi

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.