Hydrogen analysis in metal samples by selective detection method utilizing TEA CO2 laser-induced He gas plasma

When a Transversely Excited Atmospheric (TEA) CO2 laser (energy of 1.5 J, pulse duration of 200 ns) was focused on a metal sample surface containing hydrogen (H) in He gas at 1 atm, a strong helium gas plasma was produced and only H atoms came out of the sample. The H atoms then moved into the helium gas plasma to be excited through meta-stable helium atoms. Using this technique, an excellent linear calibration curve with zero intercept was made using zircalloy-2 samples containing H (100–600 ppm), where the compensation method was made using an emission intensity of O I 777.1 nm in order to subtract the H emission intensity coming from unwanted H2O. It should be emphasized that this technique has a possibility to realize highly sensitive analysis of H with a detection limit of less than 1 ppm because of its selective detection.