Hydrogen retention in lithium on metallic walls from “in vacuo” analysis in LTX and implications for high-Z plasma-facing components in NSTX-U

Kaita, R.; Lucia, M.; Allain, J. P.; Bedoya, F.; Bell, R.; Boyle, D.; Capece, A.; Jaworski, M.; Koel, B. E.; Majeski, R.; Roszell, J.; Schmitt, J.; Scotti, F.; Skinner, C. H.; Soukhanovskii, V.

doi:10.1016/j.fusengdes.2016.06.056

Title: Hydrogen retention in lithium on metallic walls from “in vacuo” analysis in LTX and implications for high-Z plasma-facing components in NSTX-U

Abstract

The application of lithium to plasma-facing components (PFCs) has long been used as a technique for wall conditioning in magnetic confinement devices to improve plasma performance. Determining the characteristics of PFCs at the time of exposure to the plasma, however, is difficult because they can only be analyzed after venting the vacuum vessel and removing them at the end of an operational period. The Materials Analysis and Particle Probe (MAPP) addresses this problem here by enabling PFC samples to be exposed to plasmas, and then withdrawn into an analysis chamber without breaking vacuum. The MAPP system was used to introduce samples that matched the metallic PFCs of the Lithium Tokamak Experiment (LTX). Lithium that was subsequently evaporated onto the walls also covered the MAPP samples, which were then subject to LTX discharges. In vacuo extraction and analysis of the samples indicated that lithium oxide formed on the PFCs, but improved plasma performance persisted in LTX. The reduced recycling this suggests is consistent with separate surface science experiments that demonstrated deuterium retention in the presence of lithium oxide films. Since oxygen decreases the thermal stability of the deuterium in the film, the release of deuterium was observed below the lithium deuteridemore »« less

Authors:

Kaita, R. ^[1]; Lucia, M. ^[1]; Allain, J. P. ^[2]; Bedoya, F. ^[2]; Bell, R. ^[1]; Boyle, D. ^[1]; Capece, A. ^[3]; Jaworski, M. ^[1]; Koel, B. E. ^[4]; Majeski, R. ^[1]; Roszell, J. ^[4]; Schmitt, J. ^[1]; Scotti, F. ^[5]; Skinner, C. H. ^[1]; Soukhanovskii, V. ^[5]

Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Univ. of Illinois, Urbana, IL (United States). Dept. of Nuclear, Plasma, & Radiological Engineering
The College of New Jersey, Ewing, NJ (United States). Dept. of Physics
Princeton Univ., NJ (United States). Dept. of Chemical & Biological Engineering
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Publication Date:: Mon Jul 18 00:00:00 EDT 2016

Research Org.:: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States); Univ. of Illinois at Urbana-Champaign, IL (United States)

Sponsoring Org.:: USDOE Office of Science (SC), Fusion Energy Sciences (FES)

OSTI Identifier:: 1512618

Alternate Identifier(s):: OSTI ID: 1416200

Report Number(s):: LLNL-JRNL-771458
Journal ID: ISSN 0920-3796; 960989

Grant/Contract Number:: AC52-07NA27344; AC02-09CH11466; SC0010717

Resource Type:: Accepted Manuscript

Journal Name:: Fusion Engineering and Design

Additional Journal Information:: Journal Volume: 117; Journal ID: ISSN 0920-3796

Publisher:: Elsevier

Country of Publication:: United States

Language:: English

Subject:: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 42 ENGINEERING; lithium; plasma-surface interactions; materials science and technology

Citation Formats


                    Kaita, R., Lucia, M., Allain, J. P., Bedoya, F., Bell, R., Boyle, D., Capece, A., Jaworski, M., Koel, B. E., Majeski, R., Roszell, J., Schmitt, J., Scotti, F., Skinner, C. H., and Soukhanovskii, V. Hydrogen retention in lithium on metallic walls from “in vacuo” analysis in LTX and implications for high-Z plasma-facing components in NSTX-U.  United States: N. p., 2016. 
Web.  doi:10.1016/j.fusengdes.2016.06.056.

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                    Kaita, R., Lucia, M., Allain, J. P., Bedoya, F., Bell, R., Boyle, D., Capece, A., Jaworski, M., Koel, B. E., Majeski, R., Roszell, J., Schmitt, J., Scotti, F., Skinner, C. H., & Soukhanovskii, V. Hydrogen retention in lithium on metallic walls from “in vacuo” analysis in LTX and implications for high-Z plasma-facing components in NSTX-U.  United States.  https://doi.org/10.1016/j.fusengdes.2016.06.056

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                    Kaita, R., Lucia, M., Allain, J. P., Bedoya, F., Bell, R., Boyle, D., Capece, A., Jaworski, M., Koel, B. E., Majeski, R., Roszell, J., Schmitt, J., Scotti, F., Skinner, C. H., and Soukhanovskii, V. Mon .  
"Hydrogen retention in lithium on metallic walls from “in vacuo” analysis in LTX and implications for high-Z plasma-facing components in NSTX-U".  United States.  https://doi.org/10.1016/j.fusengdes.2016.06.056.  https://www.osti.gov/servlets/purl/1512618.

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@article{osti_1512618,

  title        = {Hydrogen retention in lithium on metallic walls from “in vacuo” analysis in LTX and implications for high-Z plasma-facing components in NSTX-U},

  author       = {Kaita, R. and Lucia, M. and Allain, J. P. and Bedoya, F. and Bell, R. and Boyle, D. and Capece, A. and Jaworski, M. and Koel, B. E. and Majeski, R. and Roszell, J. and Schmitt, J. and Scotti, F. and Skinner, C. H. and Soukhanovskii, V.},

  abstractNote = {The application of lithium to plasma-facing components (PFCs) has long been used as a technique for wall conditioning in magnetic confinement devices to improve plasma performance. Determining the characteristics of PFCs at the time of exposure to the plasma, however, is difficult because they can only be analyzed after venting the vacuum vessel and removing them at the end of an operational period. The Materials Analysis and Particle Probe (MAPP) addresses this problem here by enabling PFC samples to be exposed to plasmas, and then withdrawn into an analysis chamber without breaking vacuum. The MAPP system was used to introduce samples that matched the metallic PFCs of the Lithium Tokamak Experiment (LTX). Lithium that was subsequently evaporated onto the walls also covered the MAPP samples, which were then subject to LTX discharges. In vacuo extraction and analysis of the samples indicated that lithium oxide formed on the PFCs, but improved plasma performance persisted in LTX. The reduced recycling this suggests is consistent with separate surface science experiments that demonstrated deuterium retention in the presence of lithium oxide films. Since oxygen decreases the thermal stability of the deuterium in the film, the release of deuterium was observed below the lithium deuteride dissociation temperature. This may explain what occurred when lithium was applied to the surface of the NSTX Liquid Lithium Divertor (LLD). The LLD had segments with individual heaters, and the deuterium-alpha emission was clearly lower in the cooler regions. The plan for NSTX-U is to replace the graphite tiles with high-Z PFCs, and apply lithium to their surfaces with lithium evaporation. Experiments with lithium coatings on such PFCs suggest that deuterium could still be retained if lithium compounds form, but limiting their surface temperatures may be necessary.},

  doi          = {10.1016/j.fusengdes.2016.06.056},

  journal      = {Fusion Engineering and Design},

  number       = ,

  volume       = 117,

  place        = {United States},

  year         = {Mon Jul 18 00:00:00 EDT 2016},

  month        = {Mon Jul 18 00:00:00 EDT 2016}

}

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https://doi.org/10.1016/j.fusengdes.2016.06.056

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Cited by: 16 works

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Figures / Tables:

Fig. 1: (a) Lithium to oxygen ratios obtained with XPS as a function of exposure time after lithium deposition on LTX shell surfaces. (b) Maximum plasma current achieved in LTX as a function of time after lithium deposition on LTX shell surfaces. Note that the units in the abscissa onmore »

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