A Markov chain model for a turbomolecular pump--theory and experiments

Chandran, M and Murthy, Krishna MV (1997) A Markov chain model for a turbomolecular pump--theory and experiments. In: Vacuum, 48 (11). pp. 899-911.

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Abstract

The random flow of molecules in turbomolecular pump is proved to be of Markovian type stochastic process. Two new variables-mean fast passage time and long range equilibrium probability-are related to the maximum compression ratio and the maximum flow, theoretically. An enumeration method to identify the flow pattern is adopted. The overall effective compression ratio is proved to be equal to the partial pressure ratio due to the molecules taking any one of the first passage time flow pattern for either direction of flow. A unified concept to make a selection of flow events is suggested to be included in the calculation of the probability and for the comparison of results. The influence of the backing pump and the flow at the ultimate vacuum level are quantified for the design purpose and are experimentally verified.

Item Type:	Journal Article
Publication:	Vacuum
Publisher:	Elsevier
Additional Information:	Copyright of this article belongs to Vacuum.
Department/Centre:	Division of Physical & Mathematical Sciences > Instrumentation Appiled Physics
Date Deposited:	25 Aug 2008
Last Modified:	19 Sep 2010 04:35
URI:	http://eprints.iisc.ac.in/id/eprint/10035

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