Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the density limit in the helicon plasma sources   Existence of the density limit in the helicon plasma sources is critically
revisited. The low- and high-frequency regimes of a helicon plasma source
operation are distinguished. In the low-frequency regime with $\omega <
\sqrt{\omega_{ci}\omega_{ce}}$ the density limit is deduced from the
Golant-Stix criterion of the accessibility of the lower hybrid resonance. In
the high-frequency case, $\omega > \sqrt{\omega_{ci}\omega_{ce}}$, an
appropriate limit is given by the Shamrai-Taranov criterion. Both these
criteria are closely related to the phenomenon of the coalescence of the
helicon wave with the Trivelpiece-Gould mode. We argue that theoretical density
limits are not achieved in existing devices but might be met in the future with
the increase of applied rf power.

5
The categories of this paper are: gr-qc
13
The categories of this paper are: quant-ph
4
The categories of this paper are: cond-mat
26
The categories of this paper are: bayes-an
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The categories of this paper are: astro-ph
7
The categories of this paper are: hep-th
11
The categories of this paper are: hep-lat
15
The categories of this paper are: nucl-ex
25
The categories of this paper are: patt-sol
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The categories of this paper are: q-fin
37
The categories of this paper are: supr-con
0
The categories of this paper are: hep-ph
14
The categories of this paper are: math-ph
34
The categories of this paper are: chem-ph
28
The categories of this paper are: alg-geom
35
The categories of this paper are: mtrl-th