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

Abstract

In this study, 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 themore » 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.« less

Authors:

Jaervinen, A. E.  ^[1];

• Search DOE PAGES for author "Jaervinen, A. E."
• Search DOE PAGES for ORCID "0000-0002-4525-8158"

Allen, S. L. ^[1]; Eldon, D. ^[2]; Fenstermacher, M. E. ^[1]; Groth, M. ^[3]; Hill, D. N. ^[2]; Lasnier, C. J. ^[1]; Leonard, A. W.  ^[2];

• Search DOE PAGES for author "Leonard, A. W."
• Search DOE PAGES for ORCID "0000-0001-9356-1074"

McLean, A. G. ^[1]; Moser, A. L. ^[2]; Porter, G. D. ^[1]; Rognlien, T. D. ^[1]; Samuell, C. M. ^[1]; Wang, H. Q. ^[2]; Watkins, J. G. ^[4]

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+ Show Author Affiliations

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:

Thu Mar 12 00:00:00 EDT 2020

Research Org.:

Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); General Atomics, San Diego, CA (United States); Sandia National Lab. (SNL-NM), Albuquerque, NM (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; OSTI ID: 1778066

Report Number(s):

LLNL-JRNL-780898; SAND-2021-4164J
Journal ID: ISSN 0029-5515; 975610; TRN: US2106383

Grant/Contract Number:  

AC52-07NA27344; FC02-04ER54698; AC04-94AL85000; 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; Divertor; Detachment; Radiation; Power; Exhaust; Drifts; UEDGE; VUV spectroscopy