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Title: Progress in DIII-D towards validating divertor power exhaust predictions

Abstract

UEDGE simulations highlight the role of cross-field drifts on the onset of detached conditions, and new calibrated divertor vacuum ultra violet (VUV) spectroscopy is used to challenge the predictions of radiative constituents in these simulations. UEDGE simulations for DIII-D H-mode plasmas with the open divertor with the ion ∇B-drift towards the X-point show a bifurcated onset of the low field side (LFS) divertor detachment, consistent with experimentally observed step-like detachment onset (Jaervinen A.E. et al 2018 Phys. Rev. Lett. 121 075001). The divertor plasma in the simulations exhibits hysteresis in upstream separatrix density between attached and detached solution branches. Reducing the drift magnitude by a factor of 3 eliminates the step-like detachment onset in the simulations, confirming the strong role of drifts in the bifurcated detachment onset. When measured local plasma densities and temperatures are within proximity of predicted values in the simulations, there is no shortfall of the local emission of the dominant resonant radiating lines. However, the simulations systematically predict a factor of two lower total integrated radiated power than measured by the bolometer with the difference lost through radial heat flow out of the computational domain. Even though there is no shortfall in the emission of themore » dominant lines, a shortfall of total radiated power can be caused by underpredicted spatial extent of the radiation front, indicating a potential upstream or divertor transport physics origin for the radiation shortfall, or shortfall of radiated power in the spectrum between the dominant lines. In addition to the underpredicted spatial extent, in detached conditions, the simulations overpredict the peak radiation and dominant carbon lines near the X-point, which can be alleviated by manually increasing divertor diffusivity in the simulations, highlighting the ad hoc cross-field transport as one of the key limitations of the predictive capability of these divertor fluid codes.« less

Authors:
ORCiD logo [1];  [1];  [2];  [1];  [3];  [2];  [1]; ORCiD logo [2];  [1];  [2];  [1];  [1];  [1];  [2];  [4]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  2. General Atomics, San Diego, CA (United States)
  3. Aalto Univ., Espoo (Finland)
  4. Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); General Atomics, San Diego, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES)
OSTI Identifier:
1615893
Alternate Identifier(s):
OSTI ID: 1615126; OSTI ID: 1616298
Report Number(s):
LLNL-JRNL-780898
Journal ID: ISSN 0029-5515; 975610
Grant/Contract Number:  
AC52-07NA27344; FC02-04ER54698; LDRD 17-ERD-020
Resource Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 60; Journal Issue: 5; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Citation Formats

Jaervinen, A. E., Allen, S. L., Eldon, D., Fenstermacher, M. E., Groth, M., Hill, D. N., Lasnier, C. J., Leonard, A. W., McLean, A. G., Moser, A. L., Porter, G. D., Rognlien, T. D., Samuell, C. M., Wang, H. Q., and Watkins, J. G. Progress in DIII-D towards validating divertor power exhaust predictions. United States: N. p., 2020. Web. doi:10.1088/1741-4326/ab7f5c.
Jaervinen, A. E., Allen, S. L., Eldon, D., Fenstermacher, M. E., Groth, M., Hill, D. N., Lasnier, C. J., Leonard, A. W., McLean, A. G., Moser, A. L., Porter, G. D., Rognlien, T. D., Samuell, C. M., Wang, H. Q., & Watkins, J. G. Progress in DIII-D towards validating divertor power exhaust predictions. United States. doi:https://doi.org/10.1088/1741-4326/ab7f5c
Jaervinen, A. E., Allen, S. L., Eldon, D., Fenstermacher, M. E., Groth, M., Hill, D. N., Lasnier, C. J., Leonard, A. W., McLean, A. G., Moser, A. L., Porter, G. D., Rognlien, T. D., Samuell, C. M., Wang, H. Q., and Watkins, J. G. Thu . "Progress in DIII-D towards validating divertor power exhaust predictions". United States. doi:https://doi.org/10.1088/1741-4326/ab7f5c. https://www.osti.gov/servlets/purl/1615893.
@article{osti_1615893,
title = {Progress in DIII-D towards validating divertor power exhaust predictions},
author = {Jaervinen, A. E. and Allen, S. L. and Eldon, D. and Fenstermacher, M. E. and Groth, M. and Hill, D. N. and Lasnier, C. J. and Leonard, A. W. and McLean, A. G. and Moser, A. L. and Porter, G. D. and Rognlien, T. D. and Samuell, C. M. and Wang, H. Q. and Watkins, J. G.},
abstractNote = {UEDGE simulations highlight the role of cross-field drifts on the onset of detached conditions, and new calibrated divertor vacuum ultra violet (VUV) spectroscopy is used to challenge the predictions of radiative constituents in these simulations. UEDGE simulations for DIII-D H-mode plasmas with the open divertor with the ion ∇B-drift towards the X-point show a bifurcated onset of the low field side (LFS) divertor detachment, consistent with experimentally observed step-like detachment onset (Jaervinen A.E. et al 2018 Phys. Rev. Lett. 121 075001). The divertor plasma in the simulations exhibits hysteresis in upstream separatrix density between attached and detached solution branches. Reducing the drift magnitude by a factor of 3 eliminates the step-like detachment onset in the simulations, confirming the strong role of drifts in the bifurcated detachment onset. When measured local plasma densities and temperatures are within proximity of predicted values in the simulations, there is no shortfall of the local emission of the dominant resonant radiating lines. However, the simulations systematically predict a factor of two lower total integrated radiated power than measured by the bolometer with the difference lost through radial heat flow out of the computational domain. Even though there is no shortfall in the emission of the dominant lines, a shortfall of total radiated power can be caused by underpredicted spatial extent of the radiation front, indicating a potential upstream or divertor transport physics origin for the radiation shortfall, or shortfall of radiated power in the spectrum between the dominant lines. In addition to the underpredicted spatial extent, in detached conditions, the simulations overpredict the peak radiation and dominant carbon lines near the X-point, which can be alleviated by manually increasing divertor diffusivity in the simulations, highlighting the ad hoc cross-field transport as one of the key limitations of the predictive capability of these divertor fluid codes.},
doi = {10.1088/1741-4326/ab7f5c},
journal = {Nuclear Fusion},
number = 5,
volume = 60,
place = {United States},
year = {2020},
month = {3}
}

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