Title: Analysis of drift effects on the tokamak power scrape-off width using SOLPS-ITER

Abstract

SOLPS-ITER, a comprehensive 2D scrape-off layer modeling package, is used to examine the physical mechanisms that set the scrape-off width ($${{\lambda}_{q}}$$ ) for inter-ELM power exhaust. Guided by Goldston's heuristic drift (HD) model, which shows remarkable quantitative agreement with experimental data, this research examines drift effects on $${{\lambda}_{q}}$$ in a DIII-D H-mode magnetic equilibrium. As a numerical expedient, a low target recycling coefficient of 0.9 is used in the simulations, resulting in outer target plasma that is sheath limited instead of conduction limited as in the experiment. Scrape-off layer (SOL) particle diffusivity (D_SOL) is scanned from 1 to 0.1 m2 s^–1. Across this diffusivity range, outer divertor heat flux is dominated by a narrow (~3–4mm when mapped to the outer midplane) electron convection channel associated with thermoelectric current through the SOL from outer to inner divertor. An order-unity up–down ion pressure asymmetry allows net ion drift flux across the separatrix, facilitated by an artificial mechanism that mimics the anomalous electron transport required for overall ambipolarity in the HD model. At $${{D}_{\text{SOL}}}=0.1$$ m2 s^–1, the density fall-off length is similar to the electron temperature fall-off length, as predicted by the HD model and as seen experimentally. Furthermore, this research represents a step toward a deeper understanding of the power scrape-off width, and serves as a basis for extending fluid modeling to more experimentally relevant, high-collisionality regimes.

Authors:

Meier, E. T. ^[1]; Goldston, R. J.  ^[2];

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Kaveeva, E. G. ^[3]; Makowski, M. A. ^[4]; Mordijck, S. ^[1]; Rozhansky, V. A. ^[3]; Senichenkov, I. Yu ^[3]; Voskoboynikov, S. P. ^[3]

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+ Show Author Affiliations

1. College of William and Mary, Williamsburg, VA (United States)
2. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
3. Peter the Great St. Petersburg Polytechnic Univ., St. Petersburg (Russia)
4. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Publication Date:

Wed Nov 02 00:00:00 EDT 2016

Research Org.:

Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)

Sponsoring Org.:

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

OSTI Identifier:

1335693

Alternate Identifier(s):

OSTI ID: 1330720

Grant/Contract Number:  

SC0010434

Resource Type:

Accepted Manuscript

Journal Name:

Plasma Physics and Controlled Fusion

Additional Journal Information:

Journal Volume: 58; Journal Issue: 12; Journal ID: ISSN 0741-3335

Publisher:

IOP Science

Country of Publication:

United States

Language:

English

Subject:

70 PLASMA PHYSICS AND FUSION TECHNOLOGY; power scrape-off width; heuristic drift model; plasma drifts; SOLPS-ITER