Experimental analysis and WallDYN simulations of the global nitrogen migration in ASDEX Upgrade L-mode discharges

G. Meisl, K. Schmid, M. Oberkofler, K. Krieger, S.W. Lisgo, L. Aho-Mantila, F. Reimold, T. Lunt

    Research output: Contribution to journalArticleScientificpeer-review

    4 Citations (Scopus)

    Abstract

    This work presents ASDEX Upgrade experiments, where the nitrogen deposition and re-erosion on divertor manipulator samples and the effect of its transport through the plasma were studied. These results are compared to WallDYN-DIVIMP simulations based on SOLPS plasma backgrounds and employing an improved WallDYN model, which includes the effusion of nitrogen from saturated surfaces. On one hand, this allows the WallDYN code and the new saturation model with a comprehensive data set to be benchmarked, on the other hand the simulations help in the interpretation of the experimental results. Both, experimental results and simulations, show that the N content in the region of the outer strike line reaches its steady-state value within one discharge. The simulations also reproduce the experimentally observed nitrogen content in samples exposed to N2-seeded discharges. With respect to the boron deposition, the nitrogen deposition in a non-seeded discharge and the re-erosion of nitrogen discrepancies to the WallDYN-DIVIMP simulations are observed. Based on SDTrimSP simulations, these are attributed to the missing depth resolution of the WallDYN surface model. A detailed comparison of spectroscopic measurements to WallDYN simulations, based on a novel synthetic spectroscopy diagnostic for WallDYN, shows that the nitrogen fluxes in the plasma are well described by the simulations. From a comparison of several WallDYN-DIVIMP simulations employing customized onion-skin model plasma backgrounds the physical processes controlling the nitrogen concentration in the core plasma and the applicability of onion-skin model plasma backgrounds are discussed. From these simulations the private flux zone with the gas valve, the outer baffle and the high field side main wall are identified as the main sources for the nitrogen content of the core plasma.
    Original languageEnglish
    Article number036014
    JournalNuclear Fusion
    Volume56
    Issue number3
    DOIs
    Publication statusPublished - 2016
    MoE publication typeA1 Journal article-refereed

    Fingerprint

    nitrogen
    simulation
    erosion
    gas valves
    baffles
    manipulators
    boron
    saturation
    spectroscopy

    Keywords

    • ASDEX Upgrade
    • DIVIMP
    • migration
    • nitrogen
    • plasma wall interaction
    • WallDYN

    Cite this

    Meisl, G. ; Schmid, K. ; Oberkofler, M. ; Krieger, K. ; Lisgo, S.W. ; Aho-Mantila, L. ; Reimold, F. ; Lunt, T. / Experimental analysis and WallDYN simulations of the global nitrogen migration in ASDEX Upgrade L-mode discharges. In: Nuclear Fusion. 2016 ; Vol. 56, No. 3.
    @article{b83a815e03c84e44910c7f386ef2b5f0,
    title = "Experimental analysis and WallDYN simulations of the global nitrogen migration in ASDEX Upgrade L-mode discharges",
    abstract = "This work presents ASDEX Upgrade experiments, where the nitrogen deposition and re-erosion on divertor manipulator samples and the effect of its transport through the plasma were studied. These results are compared to WallDYN-DIVIMP simulations based on SOLPS plasma backgrounds and employing an improved WallDYN model, which includes the effusion of nitrogen from saturated surfaces. On one hand, this allows the WallDYN code and the new saturation model with a comprehensive data set to be benchmarked, on the other hand the simulations help in the interpretation of the experimental results. Both, experimental results and simulations, show that the N content in the region of the outer strike line reaches its steady-state value within one discharge. The simulations also reproduce the experimentally observed nitrogen content in samples exposed to N2-seeded discharges. With respect to the boron deposition, the nitrogen deposition in a non-seeded discharge and the re-erosion of nitrogen discrepancies to the WallDYN-DIVIMP simulations are observed. Based on SDTrimSP simulations, these are attributed to the missing depth resolution of the WallDYN surface model. A detailed comparison of spectroscopic measurements to WallDYN simulations, based on a novel synthetic spectroscopy diagnostic for WallDYN, shows that the nitrogen fluxes in the plasma are well described by the simulations. From a comparison of several WallDYN-DIVIMP simulations employing customized onion-skin model plasma backgrounds the physical processes controlling the nitrogen concentration in the core plasma and the applicability of onion-skin model plasma backgrounds are discussed. From these simulations the private flux zone with the gas valve, the outer baffle and the high field side main wall are identified as the main sources for the nitrogen content of the core plasma.",
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    year = "2016",
    doi = "10.1088/0029-5515/56/3/036014",
    language = "English",
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    Experimental analysis and WallDYN simulations of the global nitrogen migration in ASDEX Upgrade L-mode discharges. / Meisl, G.; Schmid, K.; Oberkofler, M.; Krieger, K.; Lisgo, S.W.; Aho-Mantila, L.; Reimold, F.; Lunt, T.

    In: Nuclear Fusion, Vol. 56, No. 3, 036014, 2016.

    Research output: Contribution to journalArticleScientificpeer-review

    TY - JOUR

    T1 - Experimental analysis and WallDYN simulations of the global nitrogen migration in ASDEX Upgrade L-mode discharges

    AU - Meisl, G.

    AU - Schmid, K.

    AU - Oberkofler, M.

    AU - Krieger, K.

    AU - Lisgo, S.W.

    AU - Aho-Mantila, L.

    AU - Reimold, F.

    AU - Lunt, T.

    PY - 2016

    Y1 - 2016

    N2 - This work presents ASDEX Upgrade experiments, where the nitrogen deposition and re-erosion on divertor manipulator samples and the effect of its transport through the plasma were studied. These results are compared to WallDYN-DIVIMP simulations based on SOLPS plasma backgrounds and employing an improved WallDYN model, which includes the effusion of nitrogen from saturated surfaces. On one hand, this allows the WallDYN code and the new saturation model with a comprehensive data set to be benchmarked, on the other hand the simulations help in the interpretation of the experimental results. Both, experimental results and simulations, show that the N content in the region of the outer strike line reaches its steady-state value within one discharge. The simulations also reproduce the experimentally observed nitrogen content in samples exposed to N2-seeded discharges. With respect to the boron deposition, the nitrogen deposition in a non-seeded discharge and the re-erosion of nitrogen discrepancies to the WallDYN-DIVIMP simulations are observed. Based on SDTrimSP simulations, these are attributed to the missing depth resolution of the WallDYN surface model. A detailed comparison of spectroscopic measurements to WallDYN simulations, based on a novel synthetic spectroscopy diagnostic for WallDYN, shows that the nitrogen fluxes in the plasma are well described by the simulations. From a comparison of several WallDYN-DIVIMP simulations employing customized onion-skin model plasma backgrounds the physical processes controlling the nitrogen concentration in the core plasma and the applicability of onion-skin model plasma backgrounds are discussed. From these simulations the private flux zone with the gas valve, the outer baffle and the high field side main wall are identified as the main sources for the nitrogen content of the core plasma.

    AB - This work presents ASDEX Upgrade experiments, where the nitrogen deposition and re-erosion on divertor manipulator samples and the effect of its transport through the plasma were studied. These results are compared to WallDYN-DIVIMP simulations based on SOLPS plasma backgrounds and employing an improved WallDYN model, which includes the effusion of nitrogen from saturated surfaces. On one hand, this allows the WallDYN code and the new saturation model with a comprehensive data set to be benchmarked, on the other hand the simulations help in the interpretation of the experimental results. Both, experimental results and simulations, show that the N content in the region of the outer strike line reaches its steady-state value within one discharge. The simulations also reproduce the experimentally observed nitrogen content in samples exposed to N2-seeded discharges. With respect to the boron deposition, the nitrogen deposition in a non-seeded discharge and the re-erosion of nitrogen discrepancies to the WallDYN-DIVIMP simulations are observed. Based on SDTrimSP simulations, these are attributed to the missing depth resolution of the WallDYN surface model. A detailed comparison of spectroscopic measurements to WallDYN simulations, based on a novel synthetic spectroscopy diagnostic for WallDYN, shows that the nitrogen fluxes in the plasma are well described by the simulations. From a comparison of several WallDYN-DIVIMP simulations employing customized onion-skin model plasma backgrounds the physical processes controlling the nitrogen concentration in the core plasma and the applicability of onion-skin model plasma backgrounds are discussed. From these simulations the private flux zone with the gas valve, the outer baffle and the high field side main wall are identified as the main sources for the nitrogen content of the core plasma.

    KW - ASDEX Upgrade

    KW - DIVIMP

    KW - migration

    KW - nitrogen

    KW - plasma wall interaction

    KW - WallDYN

    U2 - 10.1088/0029-5515/56/3/036014

    DO - 10.1088/0029-5515/56/3/036014

    M3 - Article

    VL - 56

    JO - Nuclear Fusion

    JF - Nuclear Fusion

    SN - 0029-5515

    IS - 3

    M1 - 036014

    ER -