Modeling non-axisymmetry in the DIII-D small angle slot divertor using EMC3-EIRENE

J. D. Lore; P. C. Stangeby; H. Y. Guo; B. Covele; A. Moser; H. Frerichs

doi:10.1016/j.nme.2018.10.006

Modeling non-axisymmetry in the DIII-D small angle slot divertor using EMC3-EIRENE

J. D. Lore, P. C. Stangeby, H. Y. Guo, B. Covele, A. Moser, H. Frerichs

Power Exhaust and Particle Control

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Abstract

The 3D edge transport code EMC3-EIRENE is used to evaluate the effects of non-axisymmetric misalignment of the small angle slot (SAS) divertor on DIII-D. The SAS is a slot divertor with a close-fitting baffle designed to control neutral recycling to yield a wide region of low electron temperature across the divertor near the strike point and to achieve mitigated heat flux to the divertor at a lower upstream plasma density as compared to a more open geometry. The measured misalignment is simulated as an n = 1 sinusoidal offset in major radius of magnitude 5.1 mm, resulting in toroidally varying divertor conditions where local regions of high and low fluxes and a changing level of detachment can be supported. The trends can be understood in terms of the local incident angle of the magnetic field, the volume of the private flux plasma in the slot, and the energy losses along the field lines in the slot. The misaligned SAS is globally more attached and has a lower plasma density and particle flux than an axisymmetric solution. Computational grids limited to the radial extent of the slot result in artificially detached solutions unless the cross-field transport coefficients are reduced such that the heat flux width is smaller than the grid width.

Original language	English
Pages (from-to)	152-157
Number of pages	6
Journal	Nuclear Materials and Energy
Volume	17
DOIs	https://doi.org/10.1016/j.nme.2018.10.006
State	Published - Dec 2018

Funding

This material is based upon work supported by the U.S. Department of Energy , Office of Science, Office of Fusion Energy Sciences, using the DIII-D National Fusion Facility, a DOE Office of Science user facility, under Awards DE-FC02-04ER54698 and DE-AC05-00OR22725 . DIII-D data shown in this paper can be obtained in digital format by following the links at https://fusion.gat.com/global/D3D_DMP . Disclaimer : This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

Funders	Funder number
DOE Office of Science user facility
U.S. Department of Energy	DE-AC05-00OR22725, DE-FC02-04ER54698
Office of Science
Fusion Energy Sciences

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title = "Modeling non-axisymmetry in the DIII-D small angle slot divertor using EMC3-EIRENE",

abstract = "The 3D edge transport code EMC3-EIRENE is used to evaluate the effects of non-axisymmetric misalignment of the small angle slot (SAS) divertor on DIII-D. The SAS is a slot divertor with a close-fitting baffle designed to control neutral recycling to yield a wide region of low electron temperature across the divertor near the strike point and to achieve mitigated heat flux to the divertor at a lower upstream plasma density as compared to a more open geometry. The measured misalignment is simulated as an n = 1 sinusoidal offset in major radius of magnitude 5.1 mm, resulting in toroidally varying divertor conditions where local regions of high and low fluxes and a changing level of detachment can be supported. The trends can be understood in terms of the local incident angle of the magnetic field, the volume of the private flux plasma in the slot, and the energy losses along the field lines in the slot. The misaligned SAS is globally more attached and has a lower plasma density and particle flux than an axisymmetric solution. Computational grids limited to the radial extent of the slot result in artificially detached solutions unless the cross-field transport coefficients are reduced such that the heat flux width is smaller than the grid width.",

author = "Lore, {J. D.} and Stangeby, {P. C.} and Guo, {H. Y.} and B. Covele and A. Moser and H. Frerichs",

note = "Publisher Copyright: {\textcopyright} 2018",

year = "2018",

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doi = "10.1016/j.nme.2018.10.006",

language = "English",

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AU - Lore, J. D.

AU - Stangeby, P. C.

AU - Guo, H. Y.

AU - Covele, B.

AU - Moser, A.

AU - Frerichs, H.

PY - 2018/12

Y1 - 2018/12

N2 - The 3D edge transport code EMC3-EIRENE is used to evaluate the effects of non-axisymmetric misalignment of the small angle slot (SAS) divertor on DIII-D. The SAS is a slot divertor with a close-fitting baffle designed to control neutral recycling to yield a wide region of low electron temperature across the divertor near the strike point and to achieve mitigated heat flux to the divertor at a lower upstream plasma density as compared to a more open geometry. The measured misalignment is simulated as an n = 1 sinusoidal offset in major radius of magnitude 5.1 mm, resulting in toroidally varying divertor conditions where local regions of high and low fluxes and a changing level of detachment can be supported. The trends can be understood in terms of the local incident angle of the magnetic field, the volume of the private flux plasma in the slot, and the energy losses along the field lines in the slot. The misaligned SAS is globally more attached and has a lower plasma density and particle flux than an axisymmetric solution. Computational grids limited to the radial extent of the slot result in artificially detached solutions unless the cross-field transport coefficients are reduced such that the heat flux width is smaller than the grid width.

AB - The 3D edge transport code EMC3-EIRENE is used to evaluate the effects of non-axisymmetric misalignment of the small angle slot (SAS) divertor on DIII-D. The SAS is a slot divertor with a close-fitting baffle designed to control neutral recycling to yield a wide region of low electron temperature across the divertor near the strike point and to achieve mitigated heat flux to the divertor at a lower upstream plasma density as compared to a more open geometry. The measured misalignment is simulated as an n = 1 sinusoidal offset in major radius of magnitude 5.1 mm, resulting in toroidally varying divertor conditions where local regions of high and low fluxes and a changing level of detachment can be supported. The trends can be understood in terms of the local incident angle of the magnetic field, the volume of the private flux plasma in the slot, and the energy losses along the field lines in the slot. The misaligned SAS is globally more attached and has a lower plasma density and particle flux than an axisymmetric solution. Computational grids limited to the radial extent of the slot result in artificially detached solutions unless the cross-field transport coefficients are reduced such that the heat flux width is smaller than the grid width.

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JO - Nuclear Materials and Energy

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Modeling non-axisymmetry in the DIII-D small angle slot divertor using EMC3-EIRENE

Abstract

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