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Title: Secondary electron emission from lithium and lithium compounds

Abstract

In this work, measurements of electron-induced secondary electron emission (SEE) yields of lithium as a function of composition are presented. The results are particularly relevant for magnetic fusion devices such as tokamaks, field-reversed configurations, and stellarators that consider Li as a plasma-facing material for improved plasma confinement. SEE can reduce the sheath potential at the wall and cool electrons at the plasma edge, resulting in large power losses. These effects become significant as the SEE coefficient, γ{sub e}, approaches one, making it imperative to maintain a low yield surface. This work demonstrates that the yield from Li strongly depends on chemical composition and substantially increases after exposure to oxygen and water vapor. The total yield was measured using a retarding field analyzer in ultrahigh vacuum for primary electron energies of 20–600 eV. The effect of Li composition was determined by introducing controlled amounts of O{sub 2} and H{sub 2}O vapor while monitoring film composition with Auger electron spectroscopy and temperature programmed desorption. The results show that the energy at which γ{sub e} = 1 decreases with oxygen content and is 145 eV for a Li film that is 17% oxidized and drops to less than 25 eV for a fully oxidized film. This work hasmore » important implications for laboratory plasmas operating under realistic vacuum conditions in which oxidation significantly alters the electron emission properties of Li walls.« less

Authors:
 [1];  [2]; ;  [1];  [3]
  1. Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)
  2. (United States)
  3. Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08540 (United States)
Publication Date:
OSTI Identifier:
22590631
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 109; Journal Issue: 1; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 36 MATERIALS SCIENCE; AUGER ELECTRON SPECTROSCOPY; ELECTRON EMISSION; FIELD-REVERSED THETA PINCH DEVICES; FILMS; FIRST WALL; LITHIUM; LITHIUM COMPOUNDS; PLASMA CONFINEMENT; STELLARATORS; TOKAMAK DEVICES; WATER VAPOR

Citation Formats

Capece, A. M., E-mail: capecea@tcnj.edu, Department of Physics, The College of New Jersey, Ewing, New Jersey 08628, Patino, M. I., Raitses, Y., and Koel, B. E.. Secondary electron emission from lithium and lithium compounds. United States: N. p., 2016. Web. doi:10.1063/1.4955461.
Capece, A. M., E-mail: capecea@tcnj.edu, Department of Physics, The College of New Jersey, Ewing, New Jersey 08628, Patino, M. I., Raitses, Y., & Koel, B. E.. Secondary electron emission from lithium and lithium compounds. United States. doi:10.1063/1.4955461.
Capece, A. M., E-mail: capecea@tcnj.edu, Department of Physics, The College of New Jersey, Ewing, New Jersey 08628, Patino, M. I., Raitses, Y., and Koel, B. E.. Mon . "Secondary electron emission from lithium and lithium compounds". United States. doi:10.1063/1.4955461.
@article{osti_22590631,
title = {Secondary electron emission from lithium and lithium compounds},
author = {Capece, A. M., E-mail: capecea@tcnj.edu and Department of Physics, The College of New Jersey, Ewing, New Jersey 08628 and Patino, M. I. and Raitses, Y. and Koel, B. E.},
abstractNote = {In this work, measurements of electron-induced secondary electron emission (SEE) yields of lithium as a function of composition are presented. The results are particularly relevant for magnetic fusion devices such as tokamaks, field-reversed configurations, and stellarators that consider Li as a plasma-facing material for improved plasma confinement. SEE can reduce the sheath potential at the wall and cool electrons at the plasma edge, resulting in large power losses. These effects become significant as the SEE coefficient, γ{sub e}, approaches one, making it imperative to maintain a low yield surface. This work demonstrates that the yield from Li strongly depends on chemical composition and substantially increases after exposure to oxygen and water vapor. The total yield was measured using a retarding field analyzer in ultrahigh vacuum for primary electron energies of 20–600 eV. The effect of Li composition was determined by introducing controlled amounts of O{sub 2} and H{sub 2}O vapor while monitoring film composition with Auger electron spectroscopy and temperature programmed desorption. The results show that the energy at which γ{sub e} = 1 decreases with oxygen content and is 145 eV for a Li film that is 17% oxidized and drops to less than 25 eV for a fully oxidized film. This work has important implications for laboratory plasmas operating under realistic vacuum conditions in which oxidation significantly alters the electron emission properties of Li walls.},
doi = {10.1063/1.4955461},
journal = {Applied Physics Letters},
number = 1,
volume = 109,
place = {United States},
year = {Mon Jul 04 00:00:00 EDT 2016},
month = {Mon Jul 04 00:00:00 EDT 2016}
}