Citations:bombardment

Noun: incidence of a stream of high-energy particles

 * 1923 — K. H. Kingdon and Irving Langmuir, "The Removal of Thorium from the Surface of a Thoriated Tungsten Filament by Positive Ion Bombardment", Physical Review vol. 22
 * ...the amount of thorium sputtered off as a result of bombardment by positive ions.