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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
Pedagogical Context
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