Bursting of helium bubbles in tungsten due to helium implantation

V Kulagin and M Tsventoukh, JOURNAL OF NUCLEAR MATERIALS, 615, 155944 (2025).

DOI: 10.1016/j.jnucmat.2025.155944

Tungsten is a candidate material for plasma-facing components of fusion devices. Irradiation of tungsten with ions from helium plasma can result in the formation of a fiber-form morphology, called fuzz. The growth of tungsten fuzz is closely related to the appearance of subsurface helium bubbles. Therefore, understanding the evolution of helium bubbles is important for predictions of tungsten sustainability under fusion- relevant conditions. In particular, the behaviour of helium bubbles under irradiation with energetic helium ions, which can appear during transient events in plasma discharges or due to a high sheath potential near a tungsten component, remains unclear. Using molecular dynamics simulations, the current work attempts to broaden the knowledge about processes occurring during irradiation of subsurface helium bubbles in tungsten with helium atoms of elevated energy (100-500 eV), comparable to the total thermal energy of He atoms in a bubble. The findings suggest the existence of a fraction of helium bubbles that can burst after an impact of the incident atom within tens of picoseconds. The probability of bursting is estimated for various initial conditions and is shown to depend strongly on the surface temperature and the properties of bubbles: nucleation depth, size, and filling ratio. The described bursting events can influence the development and erosion of the tungsten surface under helium ion exposure in fusion devices.

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