A plasma spectroscopic study of molecular hydrogen and hydrocarbons in a tokamak; techniques and problems

The cross sections for production of excited H atoms by electron collisions exhibit significantly different variations with the principal quantum number of the product atoms, depending on whether the production mechanism involves dissociative excitation of H2, or direct excitation from ground‐state H atoms. It is also known that, in a tokamak plasma, the excited state which constitutes the boundary between the corona‐phase and the ladder‐like excitation‐ionization phase is located close to the states from which the lower members of Lyman or Blamer lines are emitted. On the basis of these premises we developed a method to determine the densities of atomic hydrogen, molecular hydrogen, and electrons from the observed Balmer or Lyman line intensities. We applied this method to the WT‐III tokamak and found that, in the edge region of the main plasma, the H2 density was forty times higher than the H atomic density. We discuss the possible use of a similar method for the treatment of a deuterium plasma or a pla...