Nitrogen transport in ASDEX Upgrade: Role of surface roughness and transport to the main wall

G. Meisl (Corresponding Author), M. Oberkofler, Antti Hakola, K. Krieger, K. Schmid, S.W. Lisgo, M. Mayer, A. Lahtinen, A. Drenik, S. Potzel, Leena Aho-Mantila, ASDEX Upgrade Team,

Research output: Contribution to journalArticleScientificpeer-review

4 Citations (Scopus)

Abstract

We have studied the retention of nitrogen in surfaces with varying roughness and the transport of nitrogen from the divertor to the outer midplane in experiments at the tokamak ASDEX Upgrade. To allow for a reliable identification of nitrogen retained from the plasma exposure, 5.3 · 1021 atoms of the tracer isotope 15N were injected into the private flux region of the plasma. On polished W samples exposed to the plasma in the outer divertor, the N content peaks to both sides of the strike line with an areal density of 1.5 · 102015N/m2 and drops to a value of 1.0 · 102015N/m2 in the strike line region. In contrast, the N content of samples with a rougher surface peaks at the strike line and reaches areal densities of 3.0 · 102015N/m2. The N deposition at the outer limiters was measured via samples exposed on the midplane manipulator. At the limiter position the 15N areal density reaches a value of 0.2 · 102015N/m2, only a factor of ten smaller than the areal densities in the divertor. However, a comparison to WallDYN simulations shows that the observed N content is roughly a factor of 4 smaller than the value predicted by these simulations. Possible reasons for this discrepancy are the toroidal asymmetric main wall geometry, which currently cannot be fully included in the simulations, or an enhanced re-erosion of deposited N.
Original languageEnglish
Pages (from-to)51-59
Number of pages9
JournalNuclear Materials and Energy
Volume12
DOIs
Publication statusPublished - 1 Aug 2017
MoE publication typeA1 Journal article-refereed

Fingerprint

surface roughness
Nitrogen
Surface roughness
Limiters
Plasmas
nitrogen
Radioactive tracers
Isotopes
Manipulators
simulation
Erosion
Fluxes
erosion
tracers
manipulators
Atoms
roughness
Geometry
isotopes
geometry

Keywords

  • impurity migration
  • nitrogen
  • roughness
  • Tokamak
  • WallDYN

Cite this

Meisl, G. ; Oberkofler, M. ; Hakola, Antti ; Krieger, K. ; Schmid, K. ; Lisgo, S.W. ; Mayer, M. ; Lahtinen, A. ; Drenik, A. ; Potzel, S. ; Aho-Mantila, Leena ; ASDEX Upgrade Team. / Nitrogen transport in ASDEX Upgrade : Role of surface roughness and transport to the main wall. In: Nuclear Materials and Energy. 2017 ; Vol. 12. pp. 51-59.
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abstract = "We have studied the retention of nitrogen in surfaces with varying roughness and the transport of nitrogen from the divertor to the outer midplane in experiments at the tokamak ASDEX Upgrade. To allow for a reliable identification of nitrogen retained from the plasma exposure, 5.3 · 1021 atoms of the tracer isotope 15N were injected into the private flux region of the plasma. On polished W samples exposed to the plasma in the outer divertor, the N content peaks to both sides of the strike line with an areal density of 1.5 · 1020 15N/m2 and drops to a value of 1.0 · 1020 15N/m2 in the strike line region. In contrast, the N content of samples with a rougher surface peaks at the strike line and reaches areal densities of 3.0 · 1020 15N/m2. The N deposition at the outer limiters was measured via samples exposed on the midplane manipulator. At the limiter position the 15N areal density reaches a value of 0.2 · 1020 15N/m2, only a factor of ten smaller than the areal densities in the divertor. However, a comparison to WallDYN simulations shows that the observed N content is roughly a factor of 4 smaller than the value predicted by these simulations. Possible reasons for this discrepancy are the toroidal asymmetric main wall geometry, which currently cannot be fully included in the simulations, or an enhanced re-erosion of deposited N.",
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Meisl, G, Oberkofler, M, Hakola, A, Krieger, K, Schmid, K, Lisgo, SW, Mayer, M, Lahtinen, A, Drenik, A, Potzel, S, Aho-Mantila, L, ASDEX Upgrade Team 2017, 'Nitrogen transport in ASDEX Upgrade: Role of surface roughness and transport to the main wall', Nuclear Materials and Energy, vol. 12, pp. 51-59. https://doi.org/10.1016/j.nme.2016.10.023

Nitrogen transport in ASDEX Upgrade : Role of surface roughness and transport to the main wall. / Meisl, G. (Corresponding Author); Oberkofler, M.; Hakola, Antti; Krieger, K.; Schmid, K.; Lisgo, S.W.; Mayer, M.; Lahtinen, A.; Drenik, A.; Potzel, S.; Aho-Mantila, Leena; ASDEX Upgrade Team.

In: Nuclear Materials and Energy, Vol. 12, 01.08.2017, p. 51-59.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Nitrogen transport in ASDEX Upgrade

T2 - Role of surface roughness and transport to the main wall

AU - Meisl, G.

AU - Oberkofler, M.

AU - Hakola, Antti

AU - Krieger, K.

AU - Schmid, K.

AU - Lisgo, S.W.

AU - Mayer, M.

AU - Lahtinen, A.

AU - Drenik, A.

AU - Potzel, S.

AU - Aho-Mantila, Leena

AU - ASDEX Upgrade Team

PY - 2017/8/1

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N2 - We have studied the retention of nitrogen in surfaces with varying roughness and the transport of nitrogen from the divertor to the outer midplane in experiments at the tokamak ASDEX Upgrade. To allow for a reliable identification of nitrogen retained from the plasma exposure, 5.3 · 1021 atoms of the tracer isotope 15N were injected into the private flux region of the plasma. On polished W samples exposed to the plasma in the outer divertor, the N content peaks to both sides of the strike line with an areal density of 1.5 · 1020 15N/m2 and drops to a value of 1.0 · 1020 15N/m2 in the strike line region. In contrast, the N content of samples with a rougher surface peaks at the strike line and reaches areal densities of 3.0 · 1020 15N/m2. The N deposition at the outer limiters was measured via samples exposed on the midplane manipulator. At the limiter position the 15N areal density reaches a value of 0.2 · 1020 15N/m2, only a factor of ten smaller than the areal densities in the divertor. However, a comparison to WallDYN simulations shows that the observed N content is roughly a factor of 4 smaller than the value predicted by these simulations. Possible reasons for this discrepancy are the toroidal asymmetric main wall geometry, which currently cannot be fully included in the simulations, or an enhanced re-erosion of deposited N.

AB - We have studied the retention of nitrogen in surfaces with varying roughness and the transport of nitrogen from the divertor to the outer midplane in experiments at the tokamak ASDEX Upgrade. To allow for a reliable identification of nitrogen retained from the plasma exposure, 5.3 · 1021 atoms of the tracer isotope 15N were injected into the private flux region of the plasma. On polished W samples exposed to the plasma in the outer divertor, the N content peaks to both sides of the strike line with an areal density of 1.5 · 1020 15N/m2 and drops to a value of 1.0 · 1020 15N/m2 in the strike line region. In contrast, the N content of samples with a rougher surface peaks at the strike line and reaches areal densities of 3.0 · 1020 15N/m2. The N deposition at the outer limiters was measured via samples exposed on the midplane manipulator. At the limiter position the 15N areal density reaches a value of 0.2 · 1020 15N/m2, only a factor of ten smaller than the areal densities in the divertor. However, a comparison to WallDYN simulations shows that the observed N content is roughly a factor of 4 smaller than the value predicted by these simulations. Possible reasons for this discrepancy are the toroidal asymmetric main wall geometry, which currently cannot be fully included in the simulations, or an enhanced re-erosion of deposited N.

KW - impurity migration

KW - nitrogen

KW - roughness

KW - Tokamak

KW - WallDYN

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