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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and Particle Probe (MAPP) addresses this problem here by enabling PFC samples to be exposed to plasmas, and then withdrawn into an analysis chamber without breaking vacuum.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 » 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.« less

Authors:
 [1];  [1];  [2];  [2];  [1];  [1];  [3];  [1];  [4];  [1];  [4];  [1];  [5];  [1];  [5]
  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  2. Univ. of Illinois, Urbana, IL (United States). Dept. of Nuclear, Plasma, & Radiological Engineering
  3. The College of New Jersey, Ewing, NJ (United States). Dept. of Physics
  4. Princeton Univ., NJ (United States). Dept. of Chemical & Biological Engineering
  5. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Princeton Plasma Physics Lab. (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:
Journal Article: 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.
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
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. 2016. "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.
@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},
url = {https://www.osti.gov/biblio/1512618}, journal = {Fusion Engineering and Design},
issn = {0920-3796},
number = ,
volume = 117,
place = {United States},
year = {2016},
month = {7}
}

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Cited by: 2 works
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Figures / Tables:

Fig. 1 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 » each plot are in days.« less

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Works referenced in this record:

Hydrogen Retention in Lithium on Metallic Walls from "In Vacuo" Analysis in LTX and Implications for High-Z Plasma-Facing Components in NSTX-U
dataset, January 2016


Hydrogen Retention in Lithium on Metallic Walls from “In Vacuo” Analysis in LTX and Implications for High-Z Plasma-Facing Components in NSTX-U
dataset, January 2016


Enhancement of Tokamak Fusion Test Reactor performance by lithium conditioning
journal, May 1996


Plasma response to lithium-coated plasma-facing components in the National Spherical Torus Experiment
journal, November 2009


Enhanced Energy Confinement and Performance in a Low-Recycling Tokamak
journal, August 2006


High performance discharges in the Lithium Tokamak eXperiment with liquid lithium wallsa)
journal, May 2015


Electron Temperature-Gradient Instability and Anomalous Skin Effect in Tokamaks
journal, November 1972


Deuterium and tritium experiments on TFTR
journal, December 1994


Unifying Role of Radial Electric Field Shear in the Confinement Trends of TFTR Supershot Plasmas
journal, September 1998


Compact DEMO, SlimCS: design progress and issues
journal, July 2009


Deuterium retention in liquid lithium
journal, October 2002


Surface chemistry analysis of lithium conditioned NSTX graphite tiles correlated to plasma performance
journal, December 2013


Deuterium Uptake in Magnetic-Fusion Devices with Lithium-Conditioned Carbon Walls
journal, March 2013


Materials analysis and particle probe: A compact diagnostic system for in situ analysis of plasma-facing components (invited)
journal, October 2012


Plasma facing surface composition during NSTX Li experiments
journal, July 2013


Effects of temperature and surface contamination on D retention in ultrathin Li films on TZM
journal, August 2015


NSTX plasma operation with a Liquid Lithium Divertor
journal, October 2012


Full toroidal imaging of non-axisymmetric plasma material interaction in the National Spherical Torus Experiment divertor
journal, October 2012


Li-CPS limiter in tokamak T-11M
journal, April 2003


Works referencing / citing this record:

Fusion applications for lithium: wall conditioning in magnetic confinement devices
journal, October 2019


Hydrogen Retention in Lithium on Metallic Walls from "In Vacuo" Analysis in LTX and Implications for High-Z Plasma-Facing Components in NSTX-U
dataset, January 2016


Experiments on the Frascati Tokamak Upgrade with a liquid tin limiter
journal, July 2019


Observation of Flat Electron Temperature Profiles in the Lithium Tokamak Experiment
journal, July 2017


Hydrogen Retention in Lithium on Metallic Walls from “In Vacuo” Analysis in LTX and Implications for High-Z Plasma-Facing Components in NSTX-U
dataset, January 2016


Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.