VUV spectroscopy for plasma diagnostics of an ECR ion source

Spectroscopic measurements of relative line intensities in the vacuum ultraviolet spectral range (VUV) were performed using a Giessen 5 GHz ECR ion source in order to obtain direct information about the plasma parameters. The ratio of intensities of the 2s2p 3P–2p2 3P to 2s2 1S–2s2p 1P transitions in the Be‐like isoelectronic sequence for C iii, O v, and Ne vii were measured at different gas pressures and ion source conditions. This ratio varied with changing plasma parameters. The measurement of this ratio may make possible estimation of the electron density of the ECR ion source plasma.