Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The importance of the classical channel in the impurity transport of
  optimized stellarators   In toroidal magnetic confinement devices, such as tokamaks and stellarators,
neoclassical transport is usually an order of magnitude larger than its
classical counterpart. However, when a high-collisionality species is present
in a stellarator optimized for low Pfirsch-Schl\"uter current, its classical
transport can be comparable to the neoclassical transport. In this letter, we
compare neoclassical and classical fluxes and transport coefficients calculated
for Wendelstein 7-X (W7-X) and Large Helical Device (LHD) cases. In W7-X, we
find that the classical transport of a collisional impurity is comparable to
the neoclassical transport for all radii, while it is negligible in the LHD
cases, except in the vicinity of radii where the neoclassical transport changes
sign. In the LHD case, electrostatic potential variations on the flux-surface
significantly enhance the neoclassical impurity transport, while the classical
transport is largely insensitive to this effect in the cases studied.

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The categories of this paper are: hep-lat
27
The categories of this paper are: comp-gas
29
The categories of this paper are: funct-an
5
The categories of this paper are: gr-qc
20
The categories of this paper are: acc-phys
31
The categories of this paper are: ao-sci
13
The categories of this paper are: quant-ph
23
The categories of this paper are: solv-int
18
The categories of this paper are: econ
28
The categories of this paper are: alg-geom
26
The categories of this paper are: bayes-an
37
The categories of this paper are: supr-con
9
The categories of this paper are: nlin
25
The categories of this paper are: patt-sol
36
The categories of this paper are: cmp-lg
1
The categories of this paper are: cs