Photodetachment cross-section evaluation using asymptotic considerations

Mathematical calculations are given concerningthe evaluation of the negative ions photodetachment crosssection, into a so-called saturation regime. The interactionbetween a negative ion particle beam and a laser beamis examined under theoretical aspects. A quantitative criterionS is proposed to define the saturation thresholdbetween the linear and the saturated domains, which areboth present in this saturation regime. The asymptoticbehaviours extracted at the low and high energy limits areused to determine this threshold quantitative criterion S andto evaluate also the photodetachment cross-section . Thecase of a symmetric gaussian photodetachment laser beamshape is examined according to the proposed formalism,which can be used either for the photo-detachment orphoto-ionization processes, and could be potentially usedinto technological solutions for negative ion neutralisationprocesses (such as neutral beam injector) in the futurefusion energy devices. Estimations onto the errors relatedto the use of this methodology are given.