Possible mitigation of tokamak plasma–surface interactions using thermionic divertor plates with inverse sheaths
Abstract
Recent studies demonstrate that when a plasma-facing surface emits a sufficient flux of electrons, it will form an inverse sheath. In this work, we consider a possibility of using thermionic target plates with inverse sheaths as an innovative divertor operating scenario. We derive an electron heat flux boundary condition for inverse sheaths and show that for given power exhaust into a tokamak scrape-off-layer, an inverse sheath leads to a much lower target plasma electron temperature than a conventional sheath. Low enough target plasma temperatures for radiative divertor detachment could therefore be achieved using inverse sheaths instead of the usual need to inject neutral atoms that compromise the core plasma. Other advantages of inverse sheath detachment over conventional sheath operating scenarios include (a) ion impact energies are as low as possible, minimizing sputtering and tritium implantation, (b) surface recombination heat flux is reduced due to ion flux reduction, and (c) arcs are inhibited due to the sign of the surface electric field. This paper outlines the basic properties of inverse sheath detachment and considers the feasibility of implementation. We offer recommendations for future modeling efforts needed to better understand the effects of thermionic emission in tokamaks and whether inverse sheaths presentmore »
- Authors:
-
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Publication Date:
- Research Org.:
- Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
- Sponsoring Org.:
- USDOE National Nuclear Security Administration (NNSA); Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
- OSTI Identifier:
- 1623336
- Alternate Identifier(s):
- OSTI ID: 1632930
- Report Number(s):
- LLNL-JRNL-797777
Journal ID: ISSN 1070-664X; 999617; TRN: US2106862
- Grant/Contract Number:
- AC52-07NA27344
- Resource Type:
- Journal Article: Accepted Manuscript
- Journal Name:
- Physics of Plasmas
- Additional Journal Information:
- Journal Volume: 27; Journal Issue: 4; Conference: 61.Annual Meeting of the APS Division of Plasma Physics, Fort Lauderdale, FL (United States), 21-25 Oct 2019; 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; Thermionic emission; Tritium; Deuterium; Plasma temperature; Plasma material interactions; Plasma properties and parameters; Tokamaks; Plasma sheaths; Ion sources
Citation Formats
Campanell, M. D. Possible mitigation of tokamak plasma–surface interactions using thermionic divertor plates with inverse sheaths. United States: N. p., 2020.
Web. doi:10.1063/1.5139904.
Campanell, M. D. Possible mitigation of tokamak plasma–surface interactions using thermionic divertor plates with inverse sheaths. United States. https://doi.org/10.1063/1.5139904
Campanell, M. D. 2020.
"Possible mitigation of tokamak plasma–surface interactions using thermionic divertor plates with inverse sheaths". United States. https://doi.org/10.1063/1.5139904. https://www.osti.gov/servlets/purl/1623336.
@article{osti_1623336,
title = {Possible mitigation of tokamak plasma–surface interactions using thermionic divertor plates with inverse sheaths},
author = {Campanell, M. D.},
abstractNote = {Recent studies demonstrate that when a plasma-facing surface emits a sufficient flux of electrons, it will form an inverse sheath. In this work, we consider a possibility of using thermionic target plates with inverse sheaths as an innovative divertor operating scenario. We derive an electron heat flux boundary condition for inverse sheaths and show that for given power exhaust into a tokamak scrape-off-layer, an inverse sheath leads to a much lower target plasma electron temperature than a conventional sheath. Low enough target plasma temperatures for radiative divertor detachment could therefore be achieved using inverse sheaths instead of the usual need to inject neutral atoms that compromise the core plasma. Other advantages of inverse sheath detachment over conventional sheath operating scenarios include (a) ion impact energies are as low as possible, minimizing sputtering and tritium implantation, (b) surface recombination heat flux is reduced due to ion flux reduction, and (c) arcs are inhibited due to the sign of the surface electric field. This paper outlines the basic properties of inverse sheath detachment and considers the feasibility of implementation. We offer recommendations for future modeling efforts needed to better understand the effects of thermionic emission in tokamaks and whether inverse sheaths present a viable divertor solution.},
doi = {10.1063/1.5139904},
url = {https://www.osti.gov/biblio/1623336},
journal = {Physics of Plasmas},
issn = {1070-664X},
number = 4,
volume = 27,
place = {United States},
year = {Thu Apr 09 00:00:00 EDT 2020},
month = {Thu Apr 09 00:00:00 EDT 2020}
}
Web of Science
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