Tungsten surface evolution by helium bubble nucleation, growth and rupture

Molecular dynamics simulations reveal sub-surface mechanisms likely involved in the initial formation of nanometresized 'fuzz' in tungsten exposed to low-energy helium plasmas. Helium clusters grow to over-pressurized bubbles as a result of repeated cycles of helium absorption and Frenkel pair formation. The self-interstitials either reach the surface as isolated adatoms or trap at the bubble periphery before organizing into prismatic (111) dislocation loops. Surface roughening occurs as single adatoms migrate to the surface, prismatic loops glide to the surface to form adatom islands, and ultimately as over-pressurized gas bubbles burst.