Aluminium surface morphology behaviour under high-flux helium ion bombardment

Samples of aluminium with purity 99.99% wt are irradiated with helium ion beam under ITER-like conditions using FALCON ion source. Aluminium is used as the surrogate material for plasma-material interaction studies. Typical parameters during steady-state exposure are the following: helium ion flux is 2–4 × 10²² m⁻² s⁻¹, heat flux is above 1 MW m⁻², average ion energy is of 2 keV, and the ion fluence is well above 10²⁷ m⁻². Investigation of the surface morphology with SEM shows the formation of the cone-like structures, which develop with fluence increasing. Surface features suddenly disappear at the fluence of 1.06 × 10²⁷ m⁻² and then start to grow again. Further fluence increase with step-by-step surface diagnostics shows periodical character of the surface structures growth and degradation.