2015; 24(1): 9-15
Published online February 28, 2015
Copyright © The Korean Vacuum Society.
S. R. Ina* and S. P. Kangb
aKorea Atomic Energy Research Institute, Daejeon 305-353, Korea
bWoosung Vacuum Co. Ltd., Choongnam 363-813, Korea
S. R. In
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
The practical pumping speed of a dry pump is considerably lower than the intrinsic speed because of back-streaming through finite gaps of the rotor assembly. The maximum compression ratio and the ultimate pressure of the pump are also directly influenced by the back-streaming rate. Therefore, information on the gap conductance, which determines the back-streaming characteristics of the rotor assembly, is the most important key for estimating the pumping performance of a dry pump. In this paper, the feasibility of calculating analytically the pumping performance of a multi-stage Roots pump, one of the most popular types of dry pumps, by quantifying the gap conductance in a rational way, is discussed.
Keywords: Roots pump, Gap conductance, Back-streaming, Multi-stage