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Title: Secondary electron emission from lithium and lithium compounds

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, γe, 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 O2 and H2O vapor while monitoring film composition with Auger electron spectroscopy and temperature programmed desorption. The results show that the energy at which γe = 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. Thismore » work has important implications for laboratory plasmas operating under realistic vacuum conditions in which oxidation significantly alters the electron emission properties of Li walls. Published by AIP Publishing.« less
Authors:
 [1] ;  [2] ;  [2] ;  [3]
  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); College of New Jersey, Ewing, NJ (United States)
  2. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  3. Princeton Univ., NJ (United States)
Publication Date:
OSTI Identifier:
1305393
Grant/Contract Number:
AC02-09CH11466; SC0012890; AF9550-09-1-0695; FA9550-11-1-0282
Type:
Accepted Manuscript
Journal Name:
Applied Physics Letters
Additional Journal Information:
Journal Volume: 109; Journal Issue: 1; Journal ID: ISSN 0003-6951
Publisher:
American Institute of Physics (AIP)
Research Org:
Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
Sponsoring Org:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY