Outer divertor of ASDEX Upgrade in low-density L-mode discharges in forward and reversed magnetic field: II: Analysis of local impurity migration

Leena Aho-Mantila (Corresponding Author), M. Wischmeier, K. Krieger, V. Rohde, Antti Hakola, S. Potzel, A. Kirschner, D. Borodin, ASDEX Upgrade Team

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Abstract

Part I (Aho-Mantila L. et al 2012 Nucl. Fusion 52 103006) presented a detailed analysis of outer divertor plasma conditions in low-density L-mode discharges in ASDEX Upgrade. In this paper, we analyse the local migration of carbon that originates from 13CH4 injected into these plasmas from the vertical outer target. Notable changes are observed in the local carbon deposition patterns when reversing the magnetic field in the experiments. Kinetic impurity-following simulations are performed using the 3D ERO code package with 2D background plasma solutions calculated with the SOLPS5.0 code package. The modelling shows that the measured changes are due to the changes in plasma collisionality, dissociation and ionization rates, and E × B drift of the impurities. These conditions affect the direction and rate of impurity migration inside and out of the divertor, having wider consequences on the global migration of impurities in a divertor tokamak. It is further shown that the migration pathways are largely determined by carbon ions and, hence, relevant for impurities in general. Neutral carbon and hydrocarbons are deposited only in the near vicinity of the injection, where they affect the local re-deposition efficiency. In this limited region, a perturbation of the local plasma conditions by the methane puff appears likely, yielding a significant uncertainty for interpreting the deposition efficiencies. The local deposition is largely influenced by the magnetic presheath electric field, the structure of which is the main uncertainty in the SOLPS5.0-ERO simulations.
Original languageEnglish
Article number103007
Number of pages13
JournalNuclear Fusion
Volume52
Issue number10
DOIs
Publication statusPublished - 2012
MoE publication typeA1 Journal article-refereed

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impurities
magnetic fields
carbon
reversing
methane
simulation
hydrocarbons
fusion
dissociation
injection
ionization
perturbation
electric fields
kinetics
ions

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Aho-Mantila, Leena ; Wischmeier, M. ; Krieger, K. ; Rohde, V. ; Hakola, Antti ; Potzel, S. ; Kirschner, A. ; Borodin, D. ; ASDEX Upgrade Team. / Outer divertor of ASDEX Upgrade in low-density L-mode discharges in forward and reversed magnetic field: II : Analysis of local impurity migration. In: Nuclear Fusion. 2012 ; Vol. 52, No. 10.
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abstract = "Part I (Aho-Mantila L. et al 2012 Nucl. Fusion 52 103006) presented a detailed analysis of outer divertor plasma conditions in low-density L-mode discharges in ASDEX Upgrade. In this paper, we analyse the local migration of carbon that originates from 13CH4 injected into these plasmas from the vertical outer target. Notable changes are observed in the local carbon deposition patterns when reversing the magnetic field in the experiments. Kinetic impurity-following simulations are performed using the 3D ERO code package with 2D background plasma solutions calculated with the SOLPS5.0 code package. The modelling shows that the measured changes are due to the changes in plasma collisionality, dissociation and ionization rates, and E × B drift of the impurities. These conditions affect the direction and rate of impurity migration inside and out of the divertor, having wider consequences on the global migration of impurities in a divertor tokamak. It is further shown that the migration pathways are largely determined by carbon ions and, hence, relevant for impurities in general. Neutral carbon and hydrocarbons are deposited only in the near vicinity of the injection, where they affect the local re-deposition efficiency. In this limited region, a perturbation of the local plasma conditions by the methane puff appears likely, yielding a significant uncertainty for interpreting the deposition efficiencies. The local deposition is largely influenced by the magnetic presheath electric field, the structure of which is the main uncertainty in the SOLPS5.0-ERO simulations.",
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Outer divertor of ASDEX Upgrade in low-density L-mode discharges in forward and reversed magnetic field: II : Analysis of local impurity migration. / Aho-Mantila, Leena (Corresponding Author); Wischmeier, M.; Krieger, K.; Rohde, V.; Hakola, Antti; Potzel, S.; Kirschner, A.; Borodin, D.; ASDEX Upgrade Team.

In: Nuclear Fusion, Vol. 52, No. 10, 103007, 2012.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Outer divertor of ASDEX Upgrade in low-density L-mode discharges in forward and reversed magnetic field: II

T2 - Analysis of local impurity migration

AU - Aho-Mantila, Leena

AU - Wischmeier, M.

AU - Krieger, K.

AU - Rohde, V.

AU - Hakola, Antti

AU - Potzel, S.

AU - Kirschner, A.

AU - Borodin, D.

AU - ASDEX Upgrade Team

PY - 2012

Y1 - 2012

N2 - Part I (Aho-Mantila L. et al 2012 Nucl. Fusion 52 103006) presented a detailed analysis of outer divertor plasma conditions in low-density L-mode discharges in ASDEX Upgrade. In this paper, we analyse the local migration of carbon that originates from 13CH4 injected into these plasmas from the vertical outer target. Notable changes are observed in the local carbon deposition patterns when reversing the magnetic field in the experiments. Kinetic impurity-following simulations are performed using the 3D ERO code package with 2D background plasma solutions calculated with the SOLPS5.0 code package. The modelling shows that the measured changes are due to the changes in plasma collisionality, dissociation and ionization rates, and E × B drift of the impurities. These conditions affect the direction and rate of impurity migration inside and out of the divertor, having wider consequences on the global migration of impurities in a divertor tokamak. It is further shown that the migration pathways are largely determined by carbon ions and, hence, relevant for impurities in general. Neutral carbon and hydrocarbons are deposited only in the near vicinity of the injection, where they affect the local re-deposition efficiency. In this limited region, a perturbation of the local plasma conditions by the methane puff appears likely, yielding a significant uncertainty for interpreting the deposition efficiencies. The local deposition is largely influenced by the magnetic presheath electric field, the structure of which is the main uncertainty in the SOLPS5.0-ERO simulations.

AB - Part I (Aho-Mantila L. et al 2012 Nucl. Fusion 52 103006) presented a detailed analysis of outer divertor plasma conditions in low-density L-mode discharges in ASDEX Upgrade. In this paper, we analyse the local migration of carbon that originates from 13CH4 injected into these plasmas from the vertical outer target. Notable changes are observed in the local carbon deposition patterns when reversing the magnetic field in the experiments. Kinetic impurity-following simulations are performed using the 3D ERO code package with 2D background plasma solutions calculated with the SOLPS5.0 code package. The modelling shows that the measured changes are due to the changes in plasma collisionality, dissociation and ionization rates, and E × B drift of the impurities. These conditions affect the direction and rate of impurity migration inside and out of the divertor, having wider consequences on the global migration of impurities in a divertor tokamak. It is further shown that the migration pathways are largely determined by carbon ions and, hence, relevant for impurities in general. Neutral carbon and hydrocarbons are deposited only in the near vicinity of the injection, where they affect the local re-deposition efficiency. In this limited region, a perturbation of the local plasma conditions by the methane puff appears likely, yielding a significant uncertainty for interpreting the deposition efficiencies. The local deposition is largely influenced by the magnetic presheath electric field, the structure of which is the main uncertainty in the SOLPS5.0-ERO simulations.

U2 - 10.1088/0029-5515/52/10/103007

DO - 10.1088/0029-5515/52/10/103007

M3 - Article

VL - 52

JO - Nuclear Fusion

JF - Nuclear Fusion

SN - 0029-5515

IS - 10

M1 - 103007

ER -