The effects of source temperature and characteristics on the optical emission from a gallium liquid metal ion source

Abstract

The light emitted from the region close to the tip of an emitting liquid metal ion source has been observed. It is shown that at high currents the light intensity rises almost as the cube of the current, but that the optical emission also depends on the source characteristics. A model based on the break-up of charged droplets is proposed to account for these results, thermal evaporation being found to be insignificant. Measurements of the effects of source temperature on light emission are also presented. From these measurements it is demonstrated that field ionisation cannot be responsible for the distortion of the total ion energy distribution seen at elevated temperatures.