ERO modeling and sensitivity analysis of locally enhanced beryllium erosion by magnetically connected antennas

A. Lasa, D. Borodin, J. M. Canik, C. C. Klepper, M. Groth, A. Kirschner, M. I. Airila, I. Borodkina, R. Ding

Research output: Contribution to journalArticleScientificpeer-review

4 Citations (Scopus)

Abstract

Experiments at JET showed locally enhanced, asymmetric beryllium (Be) erosion at outer wall limiters when magnetically connected ICRH antennas were in operation. A first modeling effort using the 3D erosion and scrape-off layer impurity transport modeling code ERO reproduced qualitatively the experimental outcome. However, local plasma parameters - in particular when 3D distributions are of interest - can be difficult to determine from available diagnostics and so erosion / impurity transport modeling input relies on output from other codes and simplified models, increasing uncertainties in the outcome. In the present contribution, we introduce and evaluate the impact of improved models and parameters with largest uncertainties of processes that impact impurity production and transport across the scrape-off layer, when simulated in ERO: (i) the magnetic geometry has been revised, for affecting the separatrix position (located 50-60 mm away from limiter surface) and thus the background plasma profiles; (ii) connection lengths between components, which lead to shadowing of ion fluxes, are also affected by the magnetic configuration; (iii) anomalous transport of ionized impurities, defined by the perpendicular diffusion coefficient, has been revisited; (iv) erosion yields that account for energy and angular distributions of background plasma ions under the present enhanced sheath potential and oblique magnetic field, have been introduced; (v) the effect of additional erosion sources, such as charge-exchange neutral fluxes, which are dominant in recessed areas like antennas, has been evaluated; (vi) chemically assisted release of Be in molecular form has been included. Sensitivity analysis highlights a qualitative effect (i.e. change in emission patterns) of magnetic shadowing, anomalous diffusion, and inclusion of neutral fluxes and molecular release of Be. The separatrix location, and energy and angular distribution of background plasma fluxes impact erosion quantitatively. ERO simulations that include all features described above match experimentally measured Be I (457.3 nm) and Be II (467.4 nm) signals, and erosion increases with varying ICRH antenna's RF power. However, this increase in erosion is only partially captured by ERO's emission measurements, as most contributions from plasma wetted surfaces fall outside the volume observed by sightlines.

Original languageEnglish
Article number016046
JournalNuclear Fusion
Volume58
Issue number1
DOIs
Publication statusPublished - 1 Jan 2018
MoE publication typeA1 Journal article-refereed

Fingerprint

sensitivity analysis
beryllium
erosion
antennas
impurities
energy distribution
angular distribution
sheaths
charge exchange
ions
diffusion coefficient
inclusions
output
profiles
geometry
configurations
magnetic fields

Keywords

  • beryllium erosion
  • ERO modeling
  • JET tokamak
  • plasma surface interactions
  • RF sheath potentials
  • sensitivity analysis

Cite this

Lasa, A., Borodin, D., Canik, J. M., Klepper, C. C., Groth, M., Kirschner, A., ... Ding, R. (2018). ERO modeling and sensitivity analysis of locally enhanced beryllium erosion by magnetically connected antennas. Nuclear Fusion, 58(1), [016046]. https://doi.org/10.1088/1741-4326/aa90c0
Lasa, A. ; Borodin, D. ; Canik, J. M. ; Klepper, C. C. ; Groth, M. ; Kirschner, A. ; Airila, M. I. ; Borodkina, I. ; Ding, R. / ERO modeling and sensitivity analysis of locally enhanced beryllium erosion by magnetically connected antennas. In: Nuclear Fusion. 2018 ; Vol. 58, No. 1.
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abstract = "Experiments at JET showed locally enhanced, asymmetric beryllium (Be) erosion at outer wall limiters when magnetically connected ICRH antennas were in operation. A first modeling effort using the 3D erosion and scrape-off layer impurity transport modeling code ERO reproduced qualitatively the experimental outcome. However, local plasma parameters - in particular when 3D distributions are of interest - can be difficult to determine from available diagnostics and so erosion / impurity transport modeling input relies on output from other codes and simplified models, increasing uncertainties in the outcome. In the present contribution, we introduce and evaluate the impact of improved models and parameters with largest uncertainties of processes that impact impurity production and transport across the scrape-off layer, when simulated in ERO: (i) the magnetic geometry has been revised, for affecting the separatrix position (located 50-60 mm away from limiter surface) and thus the background plasma profiles; (ii) connection lengths between components, which lead to shadowing of ion fluxes, are also affected by the magnetic configuration; (iii) anomalous transport of ionized impurities, defined by the perpendicular diffusion coefficient, has been revisited; (iv) erosion yields that account for energy and angular distributions of background plasma ions under the present enhanced sheath potential and oblique magnetic field, have been introduced; (v) the effect of additional erosion sources, such as charge-exchange neutral fluxes, which are dominant in recessed areas like antennas, has been evaluated; (vi) chemically assisted release of Be in molecular form has been included. Sensitivity analysis highlights a qualitative effect (i.e. change in emission patterns) of magnetic shadowing, anomalous diffusion, and inclusion of neutral fluxes and molecular release of Be. The separatrix location, and energy and angular distribution of background plasma fluxes impact erosion quantitatively. ERO simulations that include all features described above match experimentally measured Be I (457.3 nm) and Be II (467.4 nm) signals, and erosion increases with varying ICRH antenna's RF power. However, this increase in erosion is only partially captured by ERO's emission measurements, as most contributions from plasma wetted surfaces fall outside the volume observed by sightlines.",
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Lasa, A, Borodin, D, Canik, JM, Klepper, CC, Groth, M, Kirschner, A, Airila, MI, Borodkina, I & Ding, R 2018, 'ERO modeling and sensitivity analysis of locally enhanced beryllium erosion by magnetically connected antennas', Nuclear Fusion, vol. 58, no. 1, 016046. https://doi.org/10.1088/1741-4326/aa90c0

ERO modeling and sensitivity analysis of locally enhanced beryllium erosion by magnetically connected antennas. / Lasa, A.; Borodin, D.; Canik, J. M.; Klepper, C. C.; Groth, M.; Kirschner, A.; Airila, M. I.; Borodkina, I.; Ding, R.

In: Nuclear Fusion, Vol. 58, No. 1, 016046, 01.01.2018.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - ERO modeling and sensitivity analysis of locally enhanced beryllium erosion by magnetically connected antennas

AU - Lasa, A.

AU - Borodin, D.

AU - Canik, J. M.

AU - Klepper, C. C.

AU - Groth, M.

AU - Kirschner, A.

AU - Airila, M. I.

AU - Borodkina, I.

AU - Ding, R.

PY - 2018/1/1

Y1 - 2018/1/1

N2 - Experiments at JET showed locally enhanced, asymmetric beryllium (Be) erosion at outer wall limiters when magnetically connected ICRH antennas were in operation. A first modeling effort using the 3D erosion and scrape-off layer impurity transport modeling code ERO reproduced qualitatively the experimental outcome. However, local plasma parameters - in particular when 3D distributions are of interest - can be difficult to determine from available diagnostics and so erosion / impurity transport modeling input relies on output from other codes and simplified models, increasing uncertainties in the outcome. In the present contribution, we introduce and evaluate the impact of improved models and parameters with largest uncertainties of processes that impact impurity production and transport across the scrape-off layer, when simulated in ERO: (i) the magnetic geometry has been revised, for affecting the separatrix position (located 50-60 mm away from limiter surface) and thus the background plasma profiles; (ii) connection lengths between components, which lead to shadowing of ion fluxes, are also affected by the magnetic configuration; (iii) anomalous transport of ionized impurities, defined by the perpendicular diffusion coefficient, has been revisited; (iv) erosion yields that account for energy and angular distributions of background plasma ions under the present enhanced sheath potential and oblique magnetic field, have been introduced; (v) the effect of additional erosion sources, such as charge-exchange neutral fluxes, which are dominant in recessed areas like antennas, has been evaluated; (vi) chemically assisted release of Be in molecular form has been included. Sensitivity analysis highlights a qualitative effect (i.e. change in emission patterns) of magnetic shadowing, anomalous diffusion, and inclusion of neutral fluxes and molecular release of Be. The separatrix location, and energy and angular distribution of background plasma fluxes impact erosion quantitatively. ERO simulations that include all features described above match experimentally measured Be I (457.3 nm) and Be II (467.4 nm) signals, and erosion increases with varying ICRH antenna's RF power. However, this increase in erosion is only partially captured by ERO's emission measurements, as most contributions from plasma wetted surfaces fall outside the volume observed by sightlines.

AB - Experiments at JET showed locally enhanced, asymmetric beryllium (Be) erosion at outer wall limiters when magnetically connected ICRH antennas were in operation. A first modeling effort using the 3D erosion and scrape-off layer impurity transport modeling code ERO reproduced qualitatively the experimental outcome. However, local plasma parameters - in particular when 3D distributions are of interest - can be difficult to determine from available diagnostics and so erosion / impurity transport modeling input relies on output from other codes and simplified models, increasing uncertainties in the outcome. In the present contribution, we introduce and evaluate the impact of improved models and parameters with largest uncertainties of processes that impact impurity production and transport across the scrape-off layer, when simulated in ERO: (i) the magnetic geometry has been revised, for affecting the separatrix position (located 50-60 mm away from limiter surface) and thus the background plasma profiles; (ii) connection lengths between components, which lead to shadowing of ion fluxes, are also affected by the magnetic configuration; (iii) anomalous transport of ionized impurities, defined by the perpendicular diffusion coefficient, has been revisited; (iv) erosion yields that account for energy and angular distributions of background plasma ions under the present enhanced sheath potential and oblique magnetic field, have been introduced; (v) the effect of additional erosion sources, such as charge-exchange neutral fluxes, which are dominant in recessed areas like antennas, has been evaluated; (vi) chemically assisted release of Be in molecular form has been included. Sensitivity analysis highlights a qualitative effect (i.e. change in emission patterns) of magnetic shadowing, anomalous diffusion, and inclusion of neutral fluxes and molecular release of Be. The separatrix location, and energy and angular distribution of background plasma fluxes impact erosion quantitatively. ERO simulations that include all features described above match experimentally measured Be I (457.3 nm) and Be II (467.4 nm) signals, and erosion increases with varying ICRH antenna's RF power. However, this increase in erosion is only partially captured by ERO's emission measurements, as most contributions from plasma wetted surfaces fall outside the volume observed by sightlines.

KW - beryllium erosion

KW - ERO modeling

KW - JET tokamak

KW - plasma surface interactions

KW - RF sheath potentials

KW - sensitivity analysis

U2 - 10.1088/1741-4326/aa90c0

DO - 10.1088/1741-4326/aa90c0

M3 - Article

VL - 58

JO - Nuclear Fusion

JF - Nuclear Fusion

SN - 0029-5515

IS - 1

M1 - 016046

ER -