パイプまたはオリフィスと異径のパイプの接続部におけるコンダクタンス

抄録

The conductance at the junction of a pipe with a different radius pipe in the vacuum piping system is calculated by Monte Carlo simulation. The resulting conductance C_ab is the same whether the net flow is from the small pipe of radius a to the large pipe of radius b or vice versa and is shown as C_ab＝2C_0a/(1－(C_0a/C_0b)), where C_0a and C_0b are orifice conductance of radius a and b, respectively. This equation indicates that C_ab＝2C_0a in the case of b＝∞ i.e. C_0b＝∞. These results are consistent of the previous conclusion that there are twice the conductance of the orifice conductance on both ends of the pipe [H. Yamakawa : Vac. Surf. Sci. 65, 478 (2022)]. The conductance C_oab at the junction of an orifice of radius a with a large pipe of radius b is also calculated and obtained as C_oab＝2C_0a/(2－(C_0a/C_0b)).