Possibilities for direct optical observation of negative hydrogen ions in ion beam plasma sources via Rayleigh or Thomson scattering

The possibilities of applying optical scattering techniques to the determination of H- concentrations in plasma sources relevant to negative ion beam generation are considered. Rayleigh scattering measurements for incident wavelengths just below the H- photoionization limit appear to be only just feasible experimentally. A more promising possibility is observation of the modification in a plasma containing negative ions of the collective ion-feature in Thomson scattering. Numerical predictions of the effects of H- concentration on the spectral distribution of the ion-feature are presented. (author)