Isotope effect in plasmas driven by ECR modules towards H– and D– production

Abstract

Optimization of negative ion sources operated with deuterium may be limited by the lack of data on fundamental processes. Insight can be obtained from studies focusing on a direct comparison of and plasmas. Herein, the ECR volume negative ion source ‘Prometheus I’ operates with both and gases and the properties of the generated plasmas are probed by means of electrostatic probe and laser induced photo-detachment. A parametric study, involving pressure and microwave (2.45 GHz) power variation, reveals similar qualitative trends for most of the plasma properties in both gases. However, quantitively, differences do exist for the plasma potential, the electron density and temperature, and the negative ion to electron density ratio. Electron energy distribution functions are thus isotope dependent. Overall, nearly the same maximal and negative ion densities are achieved (i.e. ). The results are eventually elucidated with respect to the ECR heating mechanism, and the production and destruction paths of the negative ions.