Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Collisional transport of impurities with flux-surface varying density in
  stellarators   High-Z impurities in magnetic confinement devices are prone to develop
density variations on the flux-surface, which can significantly affect their
transport. In this paper, we generalize earlier analytic stellarator
calculations of the neoclassical radial impurity flux in the
mixed-collisionality regime (collisional impurity and low-collisionality bulk
ions) to include the effect of such flux-surface variations. We find that only
in the homogeneous density case is the transport of highly collisional
impurities (in the Pfirsch-Schl\"{u}ter regime) independent of the radial
electric field. We study these effects for a Wendelstein 7-X (W7-X) vacuum
field, with simple analytic models for the potential perturbation, under the
assumption that the impurity density is given by a Boltzmann response to a
perturbed potential. In the W7-X case studied, we find that larger amplitude
potential perturbations cause the radial electric field to dominate the
transport of the impurities. In addition, we find that classical impurity
transport can be larger than the neoclassical transport in W7-X.

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The categories of this paper are: acc-phys
13
The categories of this paper are: quant-ph
6
The categories of this paper are: astro-ph
17
The categories of this paper are: q-fin
28
The categories of this paper are: alg-geom
35
The categories of this paper are: mtrl-th
32
The categories of this paper are: atom-ph
24
The categories of this paper are: dg-ga
12
The categories of this paper are: nucl-th
26
The categories of this paper are: bayes-an
29
The categories of this paper are: funct-an
5
The categories of this paper are: gr-qc
30
The categories of this paper are: q-alg
34
The categories of this paper are: chem-ph
37
The categories of this paper are: supr-con
14
The categories of this paper are: math-ph