The ejection of atoms from gold crystals during proton irradiation

Protons from a Van de Graaff generator were passed through air into a 0.002-in. gold foil rolled to produce a cubic texture. The foil was cooled to prevent evaporation. A total dose of 3.4 x lO/sup 16/ protons was received by 0.1 cm/sup 2/ of the foil. The ejected atoms were collected on an Al-plated silica collector cooled to -150 C, and they were identifled by neutron activation. The results are interpreted as indicating that momentum transferred in the initial proton-atom collision is resolved into pulses travelling along the close-packed lines of atoms. If a pulse is not too far attenuated by the time it reaches the surface, the last atom is ejected. (T.R.H.)