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Application of a magnetic mass spectrometer to ionization studies in impure shock-heated argon

Sturtevant, B. (1966) Application of a magnetic mass spectrometer to ionization studies in impure shock-heated argon. Journal of Fluid Mechanics, 25 (4). pp. 641-656. ISSN 0022-1120. http://resolver.caltech.edu/CaltechAUTHORS:STUjfm66a

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Abstract

A study of the unique role of impurities in the initial stages of ionization relaxation in shock-heated argon, using a sampling mass spectrometer to determine the ionic products of the reaction, is described. The ions are extracted from the shock tube through a small orifice in the end wall after they have diffused through the dense thermal layer adjacent to the wall from the ionizing gas behind the reflected shock wave. The ion diffusion is analysed in detail to assess the possibility that the sampling process alters the reaction products. It is shown that this is unlikely because the impurities are in dilute concentration and the reaction is studied in its initial stages. This mode of sampling is compared with others. The experiments were conducted in argon at temperature of 16,600 °K and pressure of 16 mmHg with an estimated impurity level of 300 parts per million. A surprisingly large number of different ions were detected during the initial stages of ionization. O+ and H+ were found in much greater amounts than any of the other products, each being about five times more abundant than A+. The results suggest that H2O is probably quite generally the most important impurity in thermal-ionization experiments, and that ionization ‘incubation’ is due to dissociation of molecular impurities (especially H2O) before ionization commences. Possible explanations of the well-known efficiency of small amounts of impurities in initiating ionization are discussed.


Item Type:Article
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http://dx.doi.org/10.1017/S0022112066000326DOIUNSPECIFIED
Additional Information:Copyright © 1966 Cambridge University Press. Reprinted with permission. (Received 15 October 1965) The author wishes to thank Mr Charles P. Wang for his important contributions to the design of the electrical circuits, construction of the instrument, and execution of the experiments. This work was supported by NASA Grant NsG 40-60.
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NASANsG 40-60
Record Number:CaltechAUTHORS:STUjfm66a
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:STUjfm66a
Official Citation:B. Sturtevant (1966). Application of a magnetic mass spectrometer to ionization studies in impure shock-heated argon. Journal of Fluid Mechanics Digital Archive, 25, pp 641-656 doi:10.1017/S0022112066000326
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:12354
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:12 Nov 2008 23:59
Last Modified:26 Dec 2012 10:30

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