Midplane neutral density profiles in the National Spherical Torus Experiment

Stotler, D. P.; Scotti, F.; Bell, R. E.; Diallo, A.; LeBlanc, B. P.; Podesta, M.; Roquemore, A. L.; Ross, P. W.

doi:10.1063/1.4928372

Title: Midplane neutral density profiles in the National Spherical Torus Experiment

Abstract

Atomic and molecular density data in the outer midplane of NSTX [Ono et al., Nucl. Fusion 40, 557 (2000)] are inferred from tangential camera data via a forward modeling procedure using the DEGAS 2 Monte Carlo neutral transport code. The observed Balmer-β light emission data from 17 shots during the 2010 NSTX campaign display no obvious trends with discharge parameters such as the divertor Balmer-α emission level or edge deuterium ion density. Simulations of 12 time slices in 7 of these discharges produce molecular densities near the vacuum vessel wall of 2–8 × 10¹⁷ m^–3 and atomic densities ranging from 1 to 7 ×10¹⁶ m^–3; neither has a clear correlation with other parameters. Validation of the technique, begun in an earlier publication, is continued with an assessment of the sensitivity of the simulated camera image and neutral densities to uncertainties in the data input to the model. The simulated camera image is sensitive to the plasma profiles and virtually nothing else. The neutral densities at the vessel wall depend most strongly on the spatial distribution of the source; simulations with a localized neutral source yield densities within a factor of two of the baseline, uniform source, case. Furthermore, the uncertaintiesmore »« less

Authors:

Stotler, D. P. ^[1]; Scotti, F. ^[2]; Bell, R. E. ^[1]; Diallo, A. ^[1]; LeBlanc, B. P. ^[1]; Podesta, M. ^[1]; Roquemore, A. L. ^[1]; Ross, P. W. ^[1]

Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Publication Date:: Thu Aug 13 00:00:00 EDT 2015

Research Org.:: Lawrence Livermore National Lab., Livermore, CA (United States)

Sponsoring Org.:: USDOE

OSTI Identifier:: 1281661

Alternate Identifier(s):: OSTI ID: 1229611

Report Number(s):: LLNL-JRNL-676315
Journal ID: ISSN 1070-664X

Grant/Contract Number:: AC52-07NA27344; AC02-09CH11466

Resource Type:: Accepted Manuscript

Journal Name:: Physics of Plasmas

Additional Journal Information:: Journal Volume: 22; Journal Issue: 8; Journal ID: ISSN 1070-664X

Publisher:: American Institute of Physics (AIP)

Country of Publication:: United States

Language:: English

Subject:: 70 PLASMA PHYSICS AND FUSION; cameras; charge exchange reactions; brightness; calibration; ionization

Citation Formats


                    Stotler, D. P., Scotti, F., Bell, R. E., Diallo, A., LeBlanc, B. P., Podesta, M., Roquemore, A. L., and Ross, P. W. Midplane neutral density profiles in the National Spherical Torus Experiment.  United States: N. p., 2015. 
Web.  doi:10.1063/1.4928372.

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                    Stotler, D. P., Scotti, F., Bell, R. E., Diallo, A., LeBlanc, B. P., Podesta, M., Roquemore, A. L., & Ross, P. W. Midplane neutral density profiles in the National Spherical Torus Experiment.  United States.  https://doi.org/10.1063/1.4928372

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                    Stotler, D. P., Scotti, F., Bell, R. E., Diallo, A., LeBlanc, B. P., Podesta, M., Roquemore, A. L., and Ross, P. W. Thu .  
"Midplane neutral density profiles in the National Spherical Torus Experiment".  United States.  https://doi.org/10.1063/1.4928372.  https://www.osti.gov/servlets/purl/1281661.

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@article{osti_1281661,

  title        = {Midplane neutral density profiles in the National Spherical Torus Experiment},

  author       = {Stotler, D. P. and Scotti, F. and Bell, R. E. and Diallo, A. and LeBlanc, B. P. and Podesta, M. and Roquemore, A. L. and Ross, P. W.},

  abstractNote = {Atomic and molecular density data in the outer midplane of NSTX [Ono et al., Nucl. Fusion 40, 557 (2000)] are inferred from tangential camera data via a forward modeling procedure using the DEGAS 2 Monte Carlo neutral transport code. The observed Balmer-β light emission data from 17 shots during the 2010 NSTX campaign display no obvious trends with discharge parameters such as the divertor Balmer-α emission level or edge deuterium ion density. Simulations of 12 time slices in 7 of these discharges produce molecular densities near the vacuum vessel wall of 2–8 × 1017 m–3 and atomic densities ranging from 1 to 7 ×1016 m–3; neither has a clear correlation with other parameters. Validation of the technique, begun in an earlier publication, is continued with an assessment of the sensitivity of the simulated camera image and neutral densities to uncertainties in the data input to the model. The simulated camera image is sensitive to the plasma profiles and virtually nothing else. The neutral densities at the vessel wall depend most strongly on the spatial distribution of the source; simulations with a localized neutral source yield densities within a factor of two of the baseline, uniform source, case. Furthermore, the uncertainties in the neutral densities associated with other model inputs and assumptions are ≤ 50%.},

  doi          = {10.1063/1.4928372},

  journal      = {Physics of Plasmas},

  number       = 8,

  volume       = 22,

  place        = {United States},

  year         = {Thu Aug 13 00:00:00 EDT 2015},

  month        = {Thu Aug 13 00:00:00 EDT 2015}

}

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