The Research On The Diffusion And Settlement Mechanism Of Contaminants In Clean Vacuum Systems

The materials used in vacuum systems are always contaminated on the surface. These contaminants will be released again under certain conditions and then diffuse in a vacuum system. They will lead to component degradation, different degree of contamination of the vacuum system at different locations and other negative effects. This research has significant values to the researches and applications which need a clean vacuum environment.The simulation research is carried out firstly. The free molecular flow mathematical models under static and dynamic vacuums are set up according to the theoretical basis of contaminants diffusing and settling in vacuum systems. The author carried out several simulations in different saturated vapor pressure, contamitant scource shape and contamitant scource positions under static vacuum condition. The result shows that the position of the contamitant source has the greatest impact on the contamitant distribution. The closer from the contamitant source, the more contamitants there are, the shape of the contamitant also has some influences on the contamitant distribution, different saturated vapor pressure of the contamitant source doesn’t impact on the contamitant distribution, the settlement of gas contaminants has little effect on the contaminant distribution in high vacuum stystems. The author did the simulation under the dynamic vacuum when the pumping speed, the position of contamitant sources and pump exhaust port are changed. The result shows that the position of the contamitant source has a large impact on the contamitant distribution. The closer to the contamitant source, the more contamitants there are. The pumping speed effects the contaminant distribution. The larger pumping speed is, the more contaminant molecules near pump exhaust port will reduce. The pump exhaust port position also has effects on the contamitant distribution. The nearest position to the pump exhaust port is affected mostly. Therefore, factors affecting contaminant diffusion distribution must be overall considered. Experiments on contaminant diffusion distribution are carried out in a dynamic vaccum system. The result shows that the position of contamitant source has the greatest impact on the contamitant distribution.The closer to the contamitant source, the more contamitants there are. The pumping speed and pump exhaust port both have great effects on the contamitant distribution. Simulation results and experimental results are in good consistency.This paper establishes a analysis method of the distribution of contamitant diffusing in the vacuum system, so that the distribution of cabin contaminant is visual. It shows the concentration of contamitants at different spatial location more drectly. It has great significance to the practical application of controling contaminants in vacuum.