Influence of the beam intensity on hydrogen desorption under 2.5 MeV helium beam bombardment in lexan polycarbonate

Abstract

The energy deposited by MeV ions in a solid may create a cylindrical energised region expanding radially in the bulk and leading to an ejection of matter out from the bombarded surface. Here, simple description of matter ejection by MeV 4He + ions is given by considering the material alteration process. To describe the mechanisms by which atoms or molecules are released under ion bombardment, it is necessary to take into account the time dependent nature of the process and consider the whole history of the target produced during the slowing down of the projectile. As a means of acquiring more experimental data, we investigated the material structure dependence of the polymer targets sputtering yield. The evolution of the ejected species as a function of the projectile dose and beam intensity is analysed and correlated to the changes of the target structure. The process by which these effects occur is discussed in terms of latent tracks density. It is shown that atoms and/or molecules ejection can be described by two different mechanisms: a prompt emission and a thermal ejection process.