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Title: 2D imaging of helium ion velocity in the DIII-D divertor

Abstract

Two-dimensional imaging of parallel ion velocities are compared to fluid modeling simulations to understand the role of ions in determining divertor conditions and benchmark the UEDGE fluid modeling code. Pure helium discharges are used so that spectroscopic He+measurements represent the main-ion population at small electron temperatures. Electron temperatures and densities in the divertor match simulated values to within about 20-30% establishing the experiment/model match as being at least as good as those normally obtained in the more regularly simulated deuterium plasmas. He + brightness (HeII) comparison indicates that the degree of detachment is captured well by UEDGE, principally due to the inclusion of E x B drifts. Tomographically inverted Coherence Imaging Spectroscopy (CIS) measurements are used to determine the He + parallel velocities which display excellent agreement between model and experiment near the divertor target where He + is predicted to be the main-ion species and where electron-dominated physics dictates the parallel momentum balance. Upstream near the X-point where He + is a minority species and ion-dominated physics plays a more important role, there is an underestimation of the flow velocity magnitude by a factor of 2-3. Lastly, these results indicate that more effort is required to be able tomore » correctly predict ion momentum in these challenging regimes.« less

Authors:
ORCiD logo [1];  [1];  [1];  [1];  [1]; ORCiD logo [2];  [1];  [3];  [1]; ORCiD logo [4]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. Univ. of California, Los Angeles, CA (United States)
  4. Australian National Lab. Canberra, ACT (Australia)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Dept. of Energy (DOE), Washington DC (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1491642
Alternate Identifier(s):
OSTI ID: 1434565; OSTI ID: 1568884
Report Number(s):
LLNL-JRNL-744602
Journal ID: ISSN 1070-664X; 897588
Grant/Contract Number:  
AC52-07NA27344; AC05-00OR22725; FC02-04ER54698
Resource Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 25; Journal Issue: 5; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Citation Formats

Samuell, C. M., Porter, G. D., Meyer, W. H., Rognlien, T. D., Allen, S. L., Briesemeister, A., Mclean, A. G., Zeng, L., Jaervinen, A. E., and Howard, J. 2D imaging of helium ion velocity in the DIII-D divertor. United States: N. p., 2018. Web. doi:10.1063/1.5017999.
Samuell, C. M., Porter, G. D., Meyer, W. H., Rognlien, T. D., Allen, S. L., Briesemeister, A., Mclean, A. G., Zeng, L., Jaervinen, A. E., & Howard, J. 2D imaging of helium ion velocity in the DIII-D divertor. United States. doi:10.1063/1.5017999.
Samuell, C. M., Porter, G. D., Meyer, W. H., Rognlien, T. D., Allen, S. L., Briesemeister, A., Mclean, A. G., Zeng, L., Jaervinen, A. E., and Howard, J. Wed . "2D imaging of helium ion velocity in the DIII-D divertor". United States. doi:10.1063/1.5017999. https://www.osti.gov/servlets/purl/1491642.
@article{osti_1491642,
title = {2D imaging of helium ion velocity in the DIII-D divertor},
author = {Samuell, C. M. and Porter, G. D. and Meyer, W. H. and Rognlien, T. D. and Allen, S. L. and Briesemeister, A. and Mclean, A. G. and Zeng, L. and Jaervinen, A. E. and Howard, J.},
abstractNote = {Two-dimensional imaging of parallel ion velocities are compared to fluid modeling simulations to understand the role of ions in determining divertor conditions and benchmark the UEDGE fluid modeling code. Pure helium discharges are used so that spectroscopic He+measurements represent the main-ion population at small electron temperatures. Electron temperatures and densities in the divertor match simulated values to within about 20-30% establishing the experiment/model match as being at least as good as those normally obtained in the more regularly simulated deuterium plasmas. He+ brightness (HeII) comparison indicates that the degree of detachment is captured well by UEDGE, principally due to the inclusion of E x B drifts. Tomographically inverted Coherence Imaging Spectroscopy (CIS) measurements are used to determine the He+ parallel velocities which display excellent agreement between model and experiment near the divertor target where He+ is predicted to be the main-ion species and where electron-dominated physics dictates the parallel momentum balance. Upstream near the X-point where He+ is a minority species and ion-dominated physics plays a more important role, there is an underestimation of the flow velocity magnitude by a factor of 2-3. Lastly, these results indicate that more effort is required to be able to correctly predict ion momentum in these challenging regimes.},
doi = {10.1063/1.5017999},
journal = {Physics of Plasmas},
number = 5,
volume = 25,
place = {United States},
year = {2018},
month = {4}
}

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Cited by: 7 works
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Figures / Tables:

FIG. 1 FIG. 1: Last closed flux surface from EFIT reconstruction for DⅢ-D shot 166821 at 1800 ms (black). Measurement locations for Thompson Scattering (red x), Divertor Thompson Scattering (DTS) (red +), and microwave interferometry profiles (blue triangles) are overlaid. The blue shaded region corresponds to the approximate field of view ofmore » the lower divertor CIS diagnostic.« less

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Works referenced in this record:

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