Emission radiation of hydrogen and helium atoms and ions in plasma

By using a collisional-radiative model for hydrogen, we have investigated the relationship of the photon emission rate of Balmer α line to the ionization flux or to the recombination flux. In both the cases it is found that the dependence of the proportionality factor on the electron temperature and density is weak in the range of practical interest, and therefore the observed line intensity could be a measure of the ionization flux or the recombination flux. The results are supported experimentally in the Large Helical Device, where it is found the Balmer α line intensity well explains the variation of the electron density. We have extended a similar analysis to neutral and ionized helium taking, respectively, the λ667.8 nm (21P-31D) and λ468.6 nm (3-4) lines for example. The proportionality relationship between the ionization or recombination flux and the emission line intensity is confirmed. (orig.)