Title: Modeling the effect of lithium-induced pedestal profiles on scrape-off-layer turbulence and the heat flux width

Abstract

The effect of lithium (Li) wall coatings on scrape-off-layer (SOL)turbulence in the National Spherical Torus Experiment (NSTX) is modeled with the Lodestar SOLT (SOLTurbulence) code. Specifically, the implications for the SOL heat flux width of experimentally observed, Li-induced changes in the pedestal profiles are considered. The SOLT code used in the modeling has been expanded recently to include ion temperature evolution and ion diamagnetic drift effects. This work focuses on two NSTX discharges occurring pre- and with-Li deposition. The simulation density and temperature profiles are constrained, inside the last closed flux surface only, to match those measured in the two experiments, and the resulting drift-interchange-driven turbulence is explored. The effect of Li enters the simulation only through the pedestal profile constraint: Li modifies the experimental density and temperature profiles in the pedestal, and these profiles affect the simulated SOLturbulence. The power entering the SOL measured in the experiments is matched in the simulations by adjusting “free” dissipation parameters (e.g., diffusion coefficients) that are not measured directly in the experiments. With power-matching, (a) the heat flux SOL width is smaller, as observed experimentally by infrared thermography and (b) the simulated density fluctuation amplitudes are reduced with Li, as inferred for themore » experiments as well from reflectometry analysis. Furthermore, the instabilities and saturation mechanisms that underlie the SOLT model equilibria are also discussed.« less

Authors:

Russell, David A.  ^[1];

• Search DOE PAGES for author "Russell, David A."
• Search DOE PAGES for ORCID "0000-0002-6531-9421"

D'Ippolito, Daniel A.  ^[1];

• Search DOE PAGES for author "D'Ippolito, Daniel A."
• Search DOE PAGES for ORCID "0000-0002-9449-4421"

Myra, James R.  ^[1];

• Search DOE PAGES for author "Myra, James R."
• Search DOE PAGES for ORCID "0000-0001-5939-8429"

Canik, John M. ^[2]; Gray, Travis K. ^[2]; Zweben, Stewart J.  ^[3]

• Search DOE PAGES for author "Zweben, Stewart J."
• Search DOE PAGES for ORCID "0000-0002-1738-0586"

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+ Show Author Affiliations

1. Lodestar Research Corporation, Boulder, CO (United States)
2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
3. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

Publication Date:

Tue Sep 01 00:00:00 EDT 2015

Research Org.:

Lodestar Research Corp., Boulder, CO (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Fusion Energy Sciences (FES)

OSTI Identifier:

1214444

Alternate Identifier(s):

OSTI ID: 1229665; OSTI ID: 1265990

Report Number(s):

LRC-15-163
Journal ID: ISSN 1070-664X; PHPAEN

Grant/Contract Number:  

FG02-02ER54678; FG02-97ER54392; AC05-00OR22725

Resource Type:

Accepted Manuscript

Journal Name:

Physics of Plasmas

Additional Journal Information:

Journal Volume: 22; Journal Issue: 9; 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; tokamak; scrape-off layer; turbulence; heat flux width; 36 MATERIALS SCIENCE; turbulence simulations; lithium; turbulent transport processes; tokamaks; plasma turbulence