Hydrogen Degree of Dissociation in a Low Pressure Tandem Plasma Source

ABSTRACT

Hydrogen dissociation degree in an inductively-driven tandem plasma source, operating at low pressure, is measured by applying optical actinometry method with an argon gas as actinometer. The gas temperature, a parameter in the investigations, is obtained from the rotational temperature, analyzing the intensity distribution of the Fulcher-α band. Several actinometric pairs are used for examining the dissociation degree and its pressure dependence. The influence−on the results−of the difference in the excitation cross sections for argon, commonly accepted, is analyzed. Two suitable actinometric pairs are proposed, one of which can also be applied for fast monitoring of the dissociation degree.

KEYWORDS:

• actinometry
• degree of dissociation
• emission spectroscopy
• gas temperature
• inductively-driven discharge
• tandem plasma source

ACKNOWLEDGMENTS

The authors acknowledge Prof. Dr. A. Shivarova for the discussions and stimulation in the preparation of the paper. We are indebted to Dr. St. Lishev for his contribution to the probe measurements. The work is within projects DO02-267 supported by the National Science Fund of Bulgaria and it is part of the programme of the Bulgarian Association EURATOM/INRNE (task 2). Support to the experimental equipment by the National Science Fund (Bulgaria) and Sofia University through project D01-413 is also highly acknowledged.