Nitrogen dissociation in a low pressure cylindrical ICP discharge studied by actinometry and mass spectrometry

A cylindrical inductively coupled plasma source (ICPS) is optimized for nitrogen atom production. How to operate in the bright mode (H-mode) in pure nitrogen at relatively low applied power is explained. Actinometry is developed for a quantitative determination of the nitrogen dissociation fraction in the ICPS. These results are compared with those obtained outside the ICPS by modulated beam mass spectrometry. A qualitative agreement is obtained between the nitrogen dissociative fraction inside and outside the ICPS. The higher magnitude of the dissociation fraction given by mass spectrometry compared with that derived from actinometry is explained by the contribution of dissociative recombination of N2+ near the exit hole of the ICPS. A dissociation fraction of up to 0.7 is observed by mass spectrometry. Some results are also reported for argon-nitrogen gas mixtures