| 摘要 |
PURPOSE:To suppress the reverse flow of a hydrocarbon gas molecule inflowing from an oil rotary pump so as to obtain a large velocity of exhaust, by providing a selecting means of modes in which two sets of oil diffusion pumps respectively perform the single exhaust and these pumps are connected in series performing the exhaust. CONSTITUTION:In the first mode, only a valve V5 is placed in an open condition, and the inside of a vessel C is exhausted by only an oil rotary pump RP. In the second mode, the valve V5 is closed, placing valves V1, V1', V3, V4 in an open condition, and the inside of the vessel C is parallelly exhausted by two sets of oil diffusion pumps DP1, DP2. When the pressure in the vessel C is sufficiently decreased, the mode is switched to the third mode, closing the valves V1', V4, and a valve V2 is placed in an open condition. Then the vessel C is evacuated by the two sets of the oil diffusion pumps DP1, DP2 connected in series. |
