Low energy (0.5-3 keV) fast neutral lithium beam source for edge plasma density measurements

A low energy (0.2–3 keV) fast neutral lithium beam source based on a glassy β-eucryptite Li+ source was developed for high spatial resolution (0.5 cm or less) density profile measurements in edge plasmas of tokamaks and stellarators. A 10-fold higher Li+ emission was obtained from this source as compared with the traditionally used pasty sources. Space charge effects became important for the ion beam propagation at such low energies, requiring careful beam control between the accelerator and the neutralizing section. In spite of this shortcoming, an approximately 40 μA cm−2 equivalent current Li0 beam at about 2 keV was obtained.