Simulation Of Characteristics In Plasma Boundary Region

Plasma sheath forms at the junction of the plasma with the solid. In the research fields of low temperature and high temperature plasma, the characteristics of sheath play important roles in featuring the plasma behaviors.In the microelectronics industry, low temperature capacitively coupled plasma (CCP) discharges are widely used in surface treatment processes, such as etching and deposition For the reason that the bulk plasma and the substrate are connected through the sheath, the physical processes of the sheath directly affect the substrate surface structure and properties.In the second chapter, we use a hybrid model to simulate the characteristics of a collisional sheath in a capacitively coupled plasma (CCP) driven by a dual frequency source including a RF and a pulse current source applied to the same electrode. The hybrid model includes a fluid model that is used to simulate the characteristics of the collisional sheath, and a Monte-Carlo (MC) method by which the ion energy and ion angular distributions (IEDs and IADs) impinging on the substrate are obtained. We investigate the effect of the low frequency of the pulse source and the gas pressure on the characteristics of the sheath, as well as the IEDs and IADs. The results show that the pulse/RF frequency ratio and the gas pressure are crucial for the characteristics of the sheath and the IEDs. The IADs are significantly more sensitive to the gas pressure.Tokamak is a nuclear fusion device that plays an important role in the field of the high temperature plasma research. In ITER project, it also occupies a chief position In Tokamak, limiter is an effective protection of the vacuum chamber wall, therefore, the research about the limiter SOL enormously affects the development of reducing the impurities in the plasma.In the third chapter, we use the fluid model to simulate the distribution of density and parallel momentum near the Tokamak limiter Scrape-Off Layer (SOL). Schmidt number and the bulk plasma parallel momentum are considered to be changing parameters to study the characteristics mentioned above. The results show that when the Schmidt number increases, the distribution of density within the SOL becomes less affected by the bulk plasma region, while the distribution of the parallel momentum is more flattened and stable. In addition, a non-zero parallel momentum imposed to the bulk plasma region makes the limiter at the positive direction be impinged by more particles and the parallel momentum on it is larger.