Sputtering yields of pure and helium-implanted tungsten under fusion-relevant conditions calculated using molecular dynamics

Ferroni, Francesco; Hammond, Karl D.; Wirth, Brian D.

doi:10.1016/j.jnucmat.2014.12.090

Cited by 37 publications

(22 citation statements)

References 23 publications

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“…Previous theoretical and experimental studies show that the threshold energy of helium to sputter tungsten is above 105 eV [13,14]. Therefore, no erosion is expected in our experimental conditions.…”

Section: Discussionmentioning

confidence: 55%

“…The highest erosion yield for the grains with orientation close to the {100} is also observed in the Ar or Ne seeding deuterium plasma exposure experiments [16]. On the other hand, theoretical study [14] predicted that the {110} plane have a significantly higher sputtering yield than the {100} plane or the {111} plane, because the {110} plane is the most closely-packed of the three, and hence most likely to produce a direct helium−tungsten collision.…”

Section: Tungstenmentioning

confidence: 80%

“…Typical incident helium energy was mono-energetic 75 eV. This incident helium energy is slightly lower than the threshold energy of the sputtering yield for tungsten [13,14], while it is above the threshold energy for RAFM. The sample temperature was controlled to around 800 K by a combination of forced water cooling and electric heaters, taking into account the heat flux from the plasma.…”

Section: Methodsmentioning

confidence: 99%

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Surface morphology in tungsten and RAFM steel exposed to helium plasma in PSI-2

et al. 2017

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Impact of the helium plasma exposure on the surface modification in tungsten and RAFM (Reduced Activation Ferritic/Martensitic) steel have been investigated on the linear plasma device PSI-2 assuming the condition of DEMO first wall. In tungsten, a nanoscale undulating surface structure, which has a periodic arrangement, is formed under low temperature conditions below fuzz nanostructure formation threshold ∼ 1000 K. Interval and direction of the undulation shows dependence on the crystal orientation. A large variation in surface level up to 200 nm has been observed among grains at a fluence of 3 × 10 26 He/m 2 showing dependence of the surface erosion rate on the crystal orientation. The {100} plane in which the undulating surface structure is not formed shows the highest erosion rate. This significant erosion is due to the multistage sputtering through impurity. In RAFM steel, sponge-like nanostructure is developed and it grows with increasing helium fluence beyond 1 µm. In the sponge-like nanostructure, a composition change from the base material is observed in which the tungsten ratio increases while the iron ratio decreases showing differences in sputtering ratio depending on the atomic mass.

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Section: Discussionmentioning

confidence: 55%

Section: Tungstenmentioning

confidence: 80%

Section: Methodsmentioning

confidence: 99%

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Surface morphology in tungsten and RAFM steel exposed to helium plasma in PSI-2

et al. 2017

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“…Two polycrystalline tungsten samples (99.995%, Toho Kinzoku Co. Ltd.) were mechanically polished and annealed at 1773 K in vacuum for 2 h. They were exposed to a low-temperature helium plasma in the linear plasma device PSI-2 [13] in Jülich (Germany). The samples were biased at 100 V, the typical incident helium kinetic energy was expected to be 75 eV therefore below the W sputtering threshold energy by He [14]. Incident helium fluxes were estimated to be 2.3 × 10 22 He m −2 s −1 at 1053 K (high flux (HF) conditions) and 2.9 × 10 20 He m −2 s −1 at 1073 K (low flux (LF) conditions).…”

Section: Methodsmentioning

confidence: 99%

Hydrogen trapping in tungsten: impact of helium irradiation and thermal cycling

et al. 2020

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The impact of helium (He) plasma exposure with He fluxes relevant for ITER and WEST on the near-surface microstructure of polycrystalline tungsten (W) is investigated by coupling transmission electron microscopy (TEM) analysis and thermal desorption spectrometry (TDS) measurements. The samples were exposed in the PSI-2 linear plasma device to 75 eV He ions up to the fluence of 3 × 10 23 He m −2 with the surface temperature in the range 1053-1073 K. The obtained He bubbles-enriched W samples are subsequently probed with sequences of low flux and low fluence 250 eV deuterium (D) ion implantations and TDS measurements in an ultra-high-vacuum setup to study the effects of the near-surface morphology changes due to the helium irradiation on fundamental mechanisms of deuterium retention. The results obtained for two different nearsurface layer He bubbles morphologies revealed that the effects of He irradiation on D retention in W strongly depend on its subsequent thermal cycling. For annealing below 900 K, deuterium retention is similar to the one measured in pristine W. In contrast, for annealing above 1150 K, deuterium retention in the He bubbles enriched W is increased 3 to 8-fold as compared to non-damaged W. Additionally, the deuterium desorption peak shifts from 540 to 450 K. This increase of D trapping in the He bubbles enriched W annealed above 1150 K is presumably associated with a modification of the near-surface microstructure concurrent with an outgassing of He.

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“…Molecular dynamics (MD) [10][11][12][13][14][15][16][17][18][19][20][21][22][23], the binary collision approximation (BCA) [21,24,25], and several models [26,27] have been employed in simulations aimed at understanding the formation of fuzzy nanostructures. In particular, multi-scale simulations [28] are necessary to treat such complex processes as helium bubble formation and the growth of fuzzy nanostructures.…”

Section: Introductionmentioning

confidence: 99%

Triple Hybrid Simulation Method for Tungsten Fuzzy Nanostructure Formation

Ito

Takayama

Nakamura

2018

Plasma and Fusion Research

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To represent the formation of fuzzy nanostructures produced on a tungsten surface by exposure to a helium plasma, we have developed a hybrid simulation method that combines the binary collision approximation, molecular dynamics, and kinetic Monte Carlo calculations (BCA-MD-KMC). Since the MD code has been parallelized using the domain decomposition method (DDM) for execution in a multi-CPU environment, we developed the BCA code from scratch to mesh it efficiently with the DDM. The BCA-MD-KMC hybrid simulation code achieved a helium irradiation time of 0.1 seconds or longer, in spite of functioning at the level of atomic-scale models. In consequence, we have been able to observe the formation of concave and convex structures on a tungsten surface in the simulation.

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Sputtering yields of pure and helium-implanted tungsten under fusion-relevant conditions calculated using molecular dynamics

Cited by 37 publications

References 23 publications

Surface morphology in tungsten and RAFM steel exposed to helium plasma in PSI-2

Surface morphology in tungsten and RAFM steel exposed to helium plasma in PSI-2

Hydrogen trapping in tungsten: impact of helium irradiation and thermal cycling

Triple Hybrid Simulation Method for Tungsten Fuzzy Nanostructure Formation

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