Experimental Research On Edge Rotation Of A Tokamak Plasma

One of the preferred methods to achieve the controlled thermonuclear fusion is the magnetic confinement fusion device which is tokamak. To achieve the controlled thermonuclear fusion is not only need to meet Lawson criterion, but also need to keep fusion reactor can run stably for a long time. Tokamak plasma rotation was found to improve the plasma confinement and important role in the inhibition of magnetohydrodynamic (MHD) instability. Current plasma rotating momentum source mainly comes from the external momentum input, such as neutral beam injection, but limited by current technical level, external input momentum will not be able to meet the demand of the fusion reactor, so spontaneous rotation found in the plasma becomes very important, this is found in many devices. But spontaneous rotation mechanism is still not understand clearly, this requires more research.In this dissertation, we perform experiments on J-TEXT tokamak to investigate the edge plasma spontaneous rotate and rotation profile build. As the basis of experimental study, the first turn to set up the edge rotation diagnostic system (ERD) to measure the line integral spectrum of plasma impurity ion. Because the line integral signal can't correctly reflect the plasma edge toroidal rotation velocity and the distribution of ion temperature, therefore calculating the radial distribution of rotation velocity and ion temperature in two methods. The methods are simulating line integral spectrum based on a simple neoclassical impurity transport model and increasing measuring chords. In this dissertation, we adopted the second way which increase the number of measuring chords, because this method can provide enough demand for experimental study of rotation velocity and ion temperature profile. The ERD system is a passive spectrum measurement system, it will not influence plasma. Also, the optical path is silica fiber, so it is convenient to set up and test instrument, reduce the cost, also can reduce the influence of environment.In the experiment, we firstly measured the forming process of edge rotation during the establishment of plasma equilibrium. The point is the observation and analysis of the influence of different climb rates of plasma current and density on edge torodial rotation. The edge toroidal rotation at the plamsa equilibrium finished is used as comparison object. The results found that the faster plasma density climb, the higher counter-current edge torodial rotation velocity. But we haven't found the plasma current climb rate obviously affect edge toroidal rotation in the present J-TEXT discharge condition. According to the experimental results, it can be determined that the momentum source of edge toroidal rotation is already exists during the plasma equilibrium establish and plays a leading role in the formation of rotation distribution.Next, we considered the neoclassical predictions of the TF ripple loss effect, ion orbit loss effect and viscous effect during the establishment of plasma edge rotation. It found that the predictions is well matched with measurements. The neoclassical predictions turn out that the establishment of edge toroidal rotation profile is main due to the competition between the TF ripple loss effect and ion orbit loss effect in J-TEXT. The TF ripple loss effect make the edge toroidal rotaion rotate in the counter-current direction and increase the gradient of rotation. The ion orbit loss effect make the edge toroidal rotation rotate in the co-current direction. In low density plasma, the ion orbit loss effect is the dominant role, and the dominant role TF ripple loss effect in the high density plasma.Finally, we studied the experimental scaling of the factors which affecting the J-TEXT tokamak plasma edge rotation, that mainly included the plasma current, plasma density and temperature, toroidal magnetic field, magnetohydrodynamic (MHD) behavior and safety factor, etc. The aim was clearing the main factors which influencing the rotation in J-TEXT. Experimental results show that the edge rotation can accelerate to counter-current direction by increase of plasma density, increase of plasma current, suppression of MHD behavior, decrease of safety factor and the external negative bias voltage. The external resonance magnetic perturbation (RMP) can make the edge plasma rotate in the co-current direction. The experimental scaling study of edge rotation in J-TEXT confirmed that the important roles of edge intrinsic rotation are plasma density and safety factor. The turbulence theory and energy confiment region which are widely seen as dominant role on rotation, has certain extent influence in rotation.