Population Density and LTE of Excited Atoms in a Positive-Column Plasma I. Calculation on Hydroegn

Collisional-radiative model is applied to hydrogen plasma in a positive column and it is shown that as electron density increases in plasma, population density of an excited level goes, in general, along coronal and quasi- and full-saturation phases and finally reaches LTE. Atomic processes responsible for these phases are examined so that a criterion is presented for each transition between the successive phases. Further, it is proved that the validity condition for LTE proposed by Griem corresponds to the transition from the coronal to the quasi-saturation phase in a positive-column plasma.