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Title: Motion of W and He atoms during formation of W fuzz

Measurements are conducted to identify the motion of tungsten and helium atoms during the formation of tungsten fuzz. In a first series of experiments the mobility of helium within the growing fuzz was measured by adding 3He to the different stages of plasma exposure under conditions that promoted tungsten fuzz growth. Ion beam analysis was used to quantify the amount of 3He remaining in the samples following the plasma exposure. The results indicate that the retention of helium in bubbles within tungsten is a dynamic process with direct implantation rather than diffusion into the bubbles, best describing the motion of the helium atoms. In the second experiment, an isotopically enriched layer of tungsten (~92.99% 182W) is deposited on the surface of a bulk tungsten sample with the natural abundance of the isotopes. This sample is then exposed to helium plasma at the conditions necessary to support the formation of tungsten 'fuzz'. Depth profiles of the concentration of each of the tungsten isotopes are obtained using secondary ion mass spectrometry (SIMS) before and after the plasma exposure. The depth profiles clearly show mixing of tungsten atoms from the bulk sample toward the surface of the fuzz. Lastly, this supports a physicalmore » picture of the dynamic behavior of helium bubbles which, also, causes an enhanced mixing of tungsten atoms.« less
 [1] ;  [1] ;  [1] ;  [2] ;  [3]
  1. Univ. of California, San Diego, CA (United States). Center for Energy Research
  2. Max-Planck Inst. fur Plasmaphysik, Garching, (Germany)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Physics Division
Publication Date:
Grant/Contract Number:
AC05-00OR22725; FG02-07ER54912; SC0018302
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 58; Journal Issue: 6; Journal ID: ISSN 0029-5515
IOP Science
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26); USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24); European Union (EU)
Country of Publication:
United States
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; plasma-material interaction; tungsten fuzz; helium nano-bubbles
OSTI Identifier: