Numerical Simulation Research On Transport Of Charged Particle With A Current-reversal Equilibrium Configuration

As a feasible solutiong to realize the tokamak quasi steady state operation, alternationg current operation requires limited plasma density when total current overs zero. It’s available to reheat up the plasma and further produce plasma current in lower loop voltage barrier.The research of equilibrium configurations and plasma confinement with total current exceeding zero have great significance for understanding the behavior of the limited plasma density and the study of alternating current operation experiment. The main research work is as follows:First, the equilibrium configuration on the time when the total current exceeds zero in the AC operation experiment on CT-6B is achieved by numerically solving Grad-Shafranov equation used the finite element method and Gauss-Newton iterative method. The results show that: The equilibrium configuration is the current reversal equilibrium configurations with two oppositely flowing current components on the high-field side and low-field side when the total current exceeds zero.Magnetic island exists at high-field side and low-field side both, extreme value of plasma current density and pressure density is obtained near the magnetic island. The results coincide with the experimental results well.Second, the physical model of the charged particle movement is established, and the trajectories of electrons and deuterium ions are numerically calculated in the current reversal equilibrium configurations.Result indicates that: In the current reversal equilibrium configurations,particles loss a lot when initial position is located at the side of thelow-field field and high-field field; The trajectory of electrons movement is located at the initial magnetic surface and barely happens orbit loss.When the initial position is located at the side of low-field field near the plasma edge, trajectory of deuterium ions convert from passing particle orbit to lost banana particle orbit firstly, and further, to evaginable banana particle orbit when the initial angle becomes large.Location of losing region sandwiched between two extreme value points.Finally, speed sample which is satisfied with Maxwell distribution is obtained by using Monte Carlo method. The ratio of particle loss at different initial positions, as well as the loss distribution locates of the loss of particles are obtained in the current reversal equilibrium configurations. Then loss proportion of high energy alpha particles at different radial positions and the loss distribution locates of the high energy alpha particles in ITER conventional equilibrium configuration is simulated, and the total loss proportion is also calculated. Statistical results show that: In the current reversal equilibrium configurations,particles loss a lot when the initial position is located near the edge and center of plasma.At the same time, the places of the Deuterium ion flying off the plasma all are below the equatorial plane of the plasma in the low-field side, and the maximum of the loss distribution locates near the bottom of the plasma; In conventional equilibrium configuration of ITER tokamak, almost no loss of alpha ions happens when initial radial position is located ar?8.0,after ar?8.0,the loss rate becomes larger with the increase of radial location, the total high-energy alpha particle loss rate of ITER is about 0.8%.the places of the alpha ion flying off the plasma all are below the equatorial plane of the plasma, and the maximum of the loss distribution locates near the bottom of the plasma.