Charge state dependence of convoy-electron yields in fast ion-foil interaction

Sulphur ions of energy 125 MeV with initial charge states q=10+ to 16+ have been passed through 4-200 mu g cm-2 carbon foils. The generated convoy electrons which emerge from the foils in the forward direction with approximate beam velocity, have been measured. The authors find a strong dependence of the convoy electron yield on the initial charge state of the ions, suggesting that (i) convoy electrons are produced primarily by electron loss to the continuum (ELC) and (ii) the mean free path of convoy electrons is larger than that for electrons moving freely in solids.