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Title: Sheath superheat transmission due to redeposition of thermally emitted material

Abstract

A self-consistent three-dimensional numerical analysis using the newly developed BPHI-3D code was performed for the Debye/magnetic tokamak-type oblique incidence magnetic field sheath, with near-surface ionization and transport of thermally emitted surface material. The analysis uses Monte Carlo, kinetic treatment for deuterium-tritium and impurity ions/neutrals, Boltzmann/guiding-center electrons, and particle-in-cell time-independent Poisson solver. For typical predicted fusion edge plasma conditions for a liquid lithium divertor most evaporated lithium atoms--from a {approx}1 cm{sup 2} overheated spot-are ionized in the {approx}1 mm-wide magnetic sheath. These ions are strongly redeposited due to the sheath electric field. While this redeposition minimizes core plasma contamination, it increases the peak heat flux to the surface. A runaway situation is then possible due to superheating/evaporation positive feedback. Carbon may behave likewise as seen in code results obtained for a TORE SUPRA [Aymar et al., Plasma Physics and Controlled Nuclear Fusion Research (IAEA, Vienna, 1989)] carbon limiter. A semianalytic formula for sheath parameters as a function of emitted surface material flux is developed and verified with the code. (c) 2000 American Institute of Physics.

Authors:
 [1];  [1]
  1. Argonne National Laboratory, Argonne Illinois 60439 (United States)
Publication Date:
Research Org.:
Argonne National Laboratory (ANL), Argonne, IL
OSTI Identifier:
20216546
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 7; Journal Issue: 6; Other Information: PBD: Jun 2000; Journal ID: ISSN 1070-664X
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; PLASMA SHEATH; PLASMA SIMULATION; COMPUTER CODES; THREE-DIMENSIONAL CALCULATIONS; TOKAMAK DEVICES; SUPERHEATING; CARBON; DEUTERIUM; TRITIUM; DEBYE TEMPERATURE; KINETIC EQUATIONS; MONTE CARLO METHOD; THEORETICAL DATA

Citation Formats

Brooks, J. N., and Naujoks, D. Sheath superheat transmission due to redeposition of thermally emitted material. United States: N. p., 2000. Web. doi:10.1063/1.874097.
Brooks, J. N., & Naujoks, D. Sheath superheat transmission due to redeposition of thermally emitted material. United States. doi:10.1063/1.874097.
Brooks, J. N., and Naujoks, D. Thu . "Sheath superheat transmission due to redeposition of thermally emitted material". United States. doi:10.1063/1.874097.
@article{osti_20216546,
title = {Sheath superheat transmission due to redeposition of thermally emitted material},
author = {Brooks, J. N. and Naujoks, D.},
abstractNote = {A self-consistent three-dimensional numerical analysis using the newly developed BPHI-3D code was performed for the Debye/magnetic tokamak-type oblique incidence magnetic field sheath, with near-surface ionization and transport of thermally emitted surface material. The analysis uses Monte Carlo, kinetic treatment for deuterium-tritium and impurity ions/neutrals, Boltzmann/guiding-center electrons, and particle-in-cell time-independent Poisson solver. For typical predicted fusion edge plasma conditions for a liquid lithium divertor most evaporated lithium atoms--from a {approx}1 cm{sup 2} overheated spot-are ionized in the {approx}1 mm-wide magnetic sheath. These ions are strongly redeposited due to the sheath electric field. While this redeposition minimizes core plasma contamination, it increases the peak heat flux to the surface. A runaway situation is then possible due to superheating/evaporation positive feedback. Carbon may behave likewise as seen in code results obtained for a TORE SUPRA [Aymar et al., Plasma Physics and Controlled Nuclear Fusion Research (IAEA, Vienna, 1989)] carbon limiter. A semianalytic formula for sheath parameters as a function of emitted surface material flux is developed and verified with the code. (c) 2000 American Institute of Physics.},
doi = {10.1063/1.874097},
journal = {Physics of Plasmas},
issn = {1070-664X},
number = 6,
volume = 7,
place = {United States},
year = {2000},
month = {6}
}