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

    5 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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    author = "G. Meisl and M. Oberkofler and Antti Hakola and K. Krieger and K. Schmid and S.W. Lisgo and M. Mayer and A. Lahtinen and A. Drenik and S. Potzel and Leena Aho-Mantila and {ASDEX Upgrade Team}",
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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

    Y1 - 2017/8/1

    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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    U2 - 10.1016/j.nme.2016.10.023

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