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Laser photodetachment diagnostics of electronegative expanding plasmas

The study presents results from measurements of the negative hydrogen ion density b y laser photo-detachment in the expanding plasma region of an inductively-driven tandem plasma source. The results obtained show that the negative ion density and the plasma electronegativity increase with increasing the high-frequency power absorbed in the discharge. An optimum gas pressure range ((1-3) Pa) for negative ion production in the expansion chamber is observed.