Simulation Research On Plasma Transportation Regime In An Edge Tokamak Divertor

In view of elaborated research on divertor theory and reasonable control on experiments is extremely significant to make discharge the impurity from device smoothly and to realize further self-sustaining circulation. In different divertor operation regimes, the plasma, at both edge and core of Tokamak, will present a different transport condition, and the changing laws of the characteristic parameters such as density, temperature, velocity and pressure, and so forth, also have obvious differences. Moreover, the changing characteristics of the scrape-off layer region (SOL), as the connection area of plasma and wall material, directly affects the operation state of the entire device, so that the significance of the study on boundary of plasma behavior exists.Nowadays the theory is not detailed enough on Tokamak boundary of plasma in different divertor operation regimes. This master's thesis consists of four chapters,in which the plasma transportation properties are studied on the boundary of plasma, especially at the area near the divertor target. The background and the significance of the research is presented in the first chapter, we summarize the basic characteristics of the divertor and the distinction of different divertor operation regimes. We research the characteristics of the plasma presheath layer near the divertor target in detail in chapter 2, and some detailed analytical results are obtained. Based on the two-point model, we analyze, simulate and optimize the whole model of the Mach number of the plasma parallel flow, especially. We analyze and obtaine several solutions of changing trends of Mach number in a presheath of sheath-limited and conduction-limited regimes, respectively. Consequently, in the sheath-limited regime, the Mach number of the plasma parallel flow changes monotonously and increases gently at the beginning, sharply when it reaches the recycling entrance to sound. When the particle source is constant, of nilpotent exponents with the density of plasma, particle is accelerated slowest. With the increase of plasma power density, the changing slope of the Mach number is beginning more placid, particle is accelerated faster and faster, more and more in advance, and the accelerating area move to the upstream area. The results between the optimization model and the original model have subtle differences, smaller plasma speed in the same location of the optimized. In the conduction-limited regime, Mach number is almost constant near the X-point, and will quickly rise near the target in the divertor region. The change is very severe. It is different from the sheath-limited regime, anomalous transport processes play an important role in the conduction- limited regime. After optimization, the overall trend of Mach number remains the same, but in the same location, it has higher plasma speed, and the accelerating area move to upstream in advance. In chapters 3 and 4, refinement, optimization and analysis is presented on the boundary of the plasma in different transportation models. We have got more detailed model and simulation results through the dimensionless processing on various equations and coefficients. At last, we summarize the full thesis.