Title: Effects of elastic softening and helium accumulation kinetics on surface morphological evolution of plasma-facing tungsten

Abstract

Based on a continuous-domain model, capable of accessing the spatiotemporal scales relevant to fuzz formation on the surface of plasma-facing component (PFC) tungsten, we report self-consistent simulation results that elucidate the effects of elastic softening and helium (He) accumulation kinetics on the surface morphological response of PFC tungsten. The model accounts for the softening of the elastic moduli in the near-surface region of PFC tungsten, including both thermal softening at high temperature and softening due to He accumulation upon He implantation. The dependence of the elastic moduli on the He content follows an exponential scaling relation predicted by molecular-dynamics simulations, while the He content in the near-surface region of PFC tungsten evolves according to a first-order saturation kinetics, consistent with experimental and simulation results reported in the literature. We establish that this elastic softening accelerates both nanotendril growth on the PFC surface and the onset of fuzz formation. We also explore the role of the rate of He accumulation to a saturation level in the near-surface region of irradiated tungsten in the onset of fuzz formation. For PFC tungsten surfaces such as W(110) where, under typical irradiation conditions, the characteristic time scale for stress-driven surface diffusion is comparable to themore » characteristic time scale for He accumulation, we find that accelerating the rate of He accumulation accelerates the growth rate of nanotendrils emanating from the surface. Additionally, we present a systematic parametric study of the PFC surface morphological response to explore its dependence on the He accumulation kinetics that is controlled by the irradiation conditions for low-energy implantation. Finally, we introduce an incubation time for nanotendril growth on the PFC surface, a concept equivalent to that of incubation fluence discussed in the literature, to predict and explain the minimum exposure time required to observe fuzz formation on PFC tungsten surfaces.« less

Authors:

Chen, Chao-Shou  ^[1];

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• Search DOE PAGES for ORCID "0000-0003-0791-0042"

Dasgupta, Dwaipayan  ^[2];

• Search DOE PAGES for author "Dasgupta, Dwaipayan"
• Search DOE PAGES for ORCID "0000-0001-9405-922X"

Weerasinghe, Asanka  ^[1];

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• Search DOE PAGES for ORCID "0000-0001-7749-6823"

Wirth, Brian D.  ^[3];

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• Search DOE PAGES for ORCID "0000-0002-0395-0285"

Maroudas, Dimitrios  ^[1]

• Search DOE PAGES for author "Maroudas, Dimitrios"
• Search DOE PAGES for ORCID "0000-0001-9297-8839"

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+ Show Author Affiliations

1. Univ. of Massachusetts, Amherst, MA (United States)
2. Univ. of Tennessee, Knoxville, TN (United States)
3. Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Publication Date:

Sat Nov 28 00:00:00 EST 2020

Research Org.:

Univ. of Massachusetts, Amherst, MA (United States); Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Fusion Energy Sciences (FES)

OSTI Identifier:

1774797

Alternate Identifier(s):

OSTI ID: 1783329

Grant/Contract Number:  

SC0018421; SC0006661; 4000159718

Resource Type:

Accepted Manuscript

Journal Name:

Nuclear Fusion

Additional Journal Information:

Journal Volume: 61; Journal Issue: 1; Journal ID: ISSN 0029-5515

Publisher:

IOP Science

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 77 NANOSCIENCE AND NANOTECHNOLOGY; elastic softening; fuzz formation; tungsten; helium irradiation; plasma-facing components; surface morphological evolution model