U.S. Department of EnergyOffice of Scientific and Technical Information
Experimental Investigation on the effect of surface electric field in the growth of tungsten nano-tendril morphology due to low energy helium irradiation
Abstract
The mechanisms responsible for and controlling the growth of tungsten nano-tendrils (or "fuzz") under low-energy helium plasma exposure remain unclear. For the first time in nano-tendril experiments, the plasma sheath-produced electric field and the helium (He) ion energy have been decoupled, showing that the sheath electric field has little impact on nano-tendril growth, eliminating a possible cause for tendril growth. The well-established necessary growth conditions for W fuzz were maintained with He ion flux density Gamma_He > 10^21 He m^-2 s^-1, surface temperature T_s = 1273 K, He ion energy E_He = 64 eV, and He ion fluence Phi_He > 10^24 He m^-2. A grid is situated between the tungsten sample and plasma, with the grid and sample potentials independently controlled in order to control the electric field at the surface of the sample while maintaining the same incident He ion energy to the surface. A calculation of the potential profile in the drift space between the grid and sample was used to account for space charge and calculate the electric field at the surface of the sample. Tungsten fuzz formed at all electric fields tested, even near zero electric field. Also, the depth of the resulting W fuzz layermore »
- Authors:
-
- Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center; OSTI
- Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
- Publication Date:
- DOE Contract Number:
- SC0002060
- Research Org.:
- Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
- Sponsoring Org.:
- USDOE Office of Science (SC), Fusion Energy Sciences (FES)
- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY
- OSTI Identifier:
- 1878581
- DOI:
- https://doi.org/10.7910/DVN/J5HLLN
Citation Formats
Woller, Kevin, Whyte, Dennis, Wright, Graham, and Brunner, Dan. Experimental Investigation on the effect of surface electric field in the growth of tungsten nano-tendril morphology due to low energy helium irradiation. United States: N. p., 2018.
Web. doi:10.7910/DVN/J5HLLN.
Woller, Kevin, Whyte, Dennis, Wright, Graham, & Brunner, Dan. Experimental Investigation on the effect of surface electric field in the growth of tungsten nano-tendril morphology due to low energy helium irradiation. United States. doi:https://doi.org/10.7910/DVN/J5HLLN
Woller, Kevin, Whyte, Dennis, Wright, Graham, and Brunner, Dan. 2018.
"Experimental Investigation on the effect of surface electric field in the growth of tungsten nano-tendril morphology due to low energy helium irradiation". United States. doi:https://doi.org/10.7910/DVN/J5HLLN. https://www.osti.gov/servlets/purl/1878581. Pub date:Wed Sep 19 04:00:00 UTC 2018
@article{osti_1878581,
title = {Experimental Investigation on the effect of surface electric field in the growth of tungsten nano-tendril morphology due to low energy helium irradiation},
author = {Woller, Kevin and Whyte, Dennis and Wright, Graham and Brunner, Dan},
abstractNote = {The mechanisms responsible for and controlling the growth of tungsten nano-tendrils (or "fuzz") under low-energy helium plasma exposure remain unclear. For the first time in nano-tendril experiments, the plasma sheath-produced electric field and the helium (He) ion energy have been decoupled, showing that the sheath electric field has little impact on nano-tendril growth, eliminating a possible cause for tendril growth. The well-established necessary growth conditions for W fuzz were maintained with He ion flux density Gamma_He > 10^21 He m^-2 s^-1, surface temperature T_s = 1273 K, He ion energy E_He = 64 eV, and He ion fluence Phi_He > 10^24 He m^-2. A grid is situated between the tungsten sample and plasma, with the grid and sample potentials independently controlled in order to control the electric field at the surface of the sample while maintaining the same incident He ion energy to the surface. A calculation of the potential profile in the drift space between the grid and sample was used to account for space charge and calculate the electric field at the surface of the sample. Tungsten fuzz formed at all electric fields tested, even near zero electric field. Also, the depth of the resulting W fuzz layer was unaltered by the electric field when compared to the calculated depth determined from an empirical growth model. The conclusion is that the sheath electric field is not necessary to cause the changes in surface morphology.},
doi = {10.7910/DVN/J5HLLN},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Sep 19 04:00:00 UTC 2018},
month = {Wed Sep 19 04:00:00 UTC 2018}
}