Abstract

Metastable transfer emission spectroscopy (MTES) has been applied for on-line monitoring of nitrogen purity. The relative efficiencies of various purification techniques for removing oxygen- and carbon-containing impurities have been compared. Total oxygen impurities present initially at several hundred ppm are reduced to <50 ppb with a reactive resin. Several other conventional laboratory purification methods reduce, but do not eliminate, oxygen contamination. Hydrocarbon impurities as methane are reduced only to the 3 ppm level by a liquid-nitrogen cold trap. Further reduction is obtained by the use of the microwave discharge as a chemical reactor prior to liquid-nitrogen trapping. An on-line system for the direct purification and reliable monitoring of nitrogen purity in a flowing gas stream is reported.

Fiber optic Raman sensor to monitor the concentration ratio of nitrogen and oxygen in a cryogenic mixture

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