A new type of ion source

A new type of positive ion source is described, based on an electrostatic charged particle oscillator described by McIlraith in 1966. The new source is especially suitable for the controlled removal of material from solid surfaces or for the thinning of specimens for electron microscopy. Ion current densities up to 300 μA cm⁻² have been readily obtained. Large areas of sample can be bombarded and the working pressure of the device is low, normally below 10⁻³ torr. A specimen of OFHC copper exposed to a beam of argon ions at a density of 100 μA cm⁻² was eroded at the rate of 1 μm per hour, corresponding to a removal rate about four atoms per incident ion.