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Comment on ‘Information hidden in the velocity distribution of ions and the exact kinetic Bohm criterion’
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Authors
Advisor(s)
Abstract(s)
Tsankov and Czarnetzki (2017 Plasma Sources Sci. Technol. 055003) showed that
measurements with a wall-mounted plasma monitor can allow noninvasive access to spatially
resolved plasma parameters, including the ion velocity distribution. On the basis of experimental
data and numerical modeling, they proposed a new form of collisionally modified kinetic Bohm
criterion. In this work, we point out that the kinetic Bohm criterion may be written in a form that
is exactly equivalent to the original criterion but does not pose the much-debated problem of
divergence for slow ions. This form enables one to show that the kinetic Bohm criterion, as well
as the Bohm criterion for monoenergetic ions, has a distinct mathematical meaning. Collisionally
modified Bohm criteria do not possess the same, or any other, mathematical meaning. Hence,
there are no mathematical grounds for speaking of a collisionally-modified Bohm criterion and
no non-arbitrary way to introduce it. Therefore, the use of the term ‘exact kinetic Bohm criterion’
in the paper by Tsankov and Czarnetzki is hardly justified.
Description
Keywords
Sheath Plasma-sheath transition Bohm criterion . Faculdade de Ciências Exatas e da Engenharia
Citation
Benilov, M. S. (2019). Comment on ‘Information hidden in the velocity distribution of ions and the exact kinetic Bohm criterion’. Plasma Sources Science and Technology, 28(7), 078001. DOI: 10.1088/1361-6595/ab0f58
Publisher
IOP Publishing