Spectroscopic Studies of Cold Atomic Hydrogen and Deuterium Produced in a Tokamak Edge Plasma

Spectroscopic measurements of low-n Balmer line profiles of atomic hydrogen and deuterium, emitted within the edge region of the TEXTOR-94 tokamak plasma, have revealed the existence of a class of cold excited atoms, whose probable origin has been ascribed to electron impact-induced molecular dissociation. Associated with these cold radiators are a second group of ‘lukewarm’ atoms, i.e. atoms heated by elastic collisions with hot protons (deuterons) diffusing outward from the plasma interior, as well as a third group of ‘hot’ atoms, produced in the corresponding excited states directly by charge-exchange recombination between protons (deuterons) and boundary region atoms. A mechanism recently proposed to explain the heating process quantitatively, in terms of elastic atom-ion collisions, is applied and discussed in this paper.