  As impermeable to gas molecules and at the same time transparent to
high-energy ions, graphene has been suggested as a window material for
separating a high-vacuum ion beam system from targets kept at ambient
conditions. However, accumulation of irradiation-induced damage in the graphene
membrane may give rise to its mechanical failure. Using atomistic simulations,
we demonstrate that irradiated graphene even with a high vacancy concentration
does not show signs of such instability, indicating a considerable robustness
of graphene windows. We further show that upper and lower estimates for the
irradiation damage in graphene can be set using a simple model.
