SECONDARY ELECTRON EMISSION FROM THE ENTRANCE AND EXIT SURFACES OF THIN ALUMINIUM FOILS UNDER FAST LIGHT ION BOMBARDMENT.

The total secondary electron emission yield from the entrance and exit surfaces of thin aluminium foils has been measured for protons, deuterons and He beams in the Mev region. It is found that this yield for each surface decreases with the ion beam intensity and with the dose; the former may be due to a beam-induced temperature effect while the latter is attributed to an increase of the beam-induced contamination from adsorbed gases in the target. The ratio of total forward yield to the total backward yield is about a factor of 2 which is also observed to be approximately the ratio of the contamination rates of the exit surface to the entrance surface. This suggests the possibility that the secondary electron emission is directly related to the surface contamination rate.