2.6 Fueling a Fusion Reactor by the Injection of a Compact Torus Plasma
– Shedding Light on the Dynamics of the Physical Processes by Three Dimensional Simulations


This picture, (126KB)

Fig. 2-11 Three dimensional magnetohydrodynamic simulation of injection process of a CT plasma

In the target plasma the interaction of the magnetic lines of force carried by the injected CT itself with the target (tokamak) magnetic field unties the CT's own magnetic lines of force, reconnecting them with the target magnetic field (magnetic reconnection). The injected CT plasma no longer maintains its own compact structure and mixes with the target plasma. This will be a picture of fueling. Owing to the penetration process of the CT, the magnetic tension resulting from bending and stretching of the lines of force of the target field caused by the motion of the CT will act to decelerate the CT plasma.



Compact torus (CT) plasma injection into a target plasma has drawn considerable attention as an effective method of fueling core plasmas of a fusion reactor. The CT plasma is a toroidally-shaped magnetized lump of plasma (plasmoid), or a micro-sized tokamak-like plasma produced by a coaxial plasma gun equipped with a magnetization coil. Scenarios such as high speed injection of a CT to supply fuel plasma deep at the reactor core, or acceleration-controlled injection of a CT to an arbitrarily localized region in the plasma to control burning etc. will be available, and experimental studies to develop the feasibility of CT injection are under way on JFT-2M and other medium-sized tokamaks. However the physical behavior of injected CT in a tokamak plasma and the effectiveness of fueling by CT have not yet been fully understood.
We have made a detailed investigation of; the dynamics of a CT plasma in a magnetized plasma, and a theoretical model of tokamak core plasmas involving the injection and penetration processes and the deceleration mechanism of CT plasma by three dimen-sional magnetohydrodynamic simulations (Fig. 2-11). We have found the following so far; (1) An injected CT plasma goes through complicated interactions with a simulated tokamak magnetic field, resulting in magnetic reconnection, and the magnetic field is transformed into a new-configuration. As a result the CT plasma loses its entity as a plasmoid and the high density CT plasma mixes with the background tokamak plasma, and thus fueling is done. (2) Deceleration of a CT plasma is caused not only by the pressure of the tokamak magnetic field but also by the tension of its magnetic lines of force.
(3) Magnetic reconnection has a relaxation effect on the deceleration process due to the magnetic tension of lines of force. Further studies including comparison with experimental results will be continued.


Reference
Y. Suzuki* et al., Three-Dimensional Dynamics of a Compact Torus Injected into Magnetized Plasmas II, Purazuma, Kaku Yugo Gakkai-shi, 76(3), 288 (2000). *post doctoral fellow

Select a topic in left column


Persistent Quest-Research Activities 2000
Copyright(c)Japan Atomic Energy Research Institute