Molecular and Atomic Deuterium in the Plasma Edge of TEXTOR-94

Abstract

This paper gives a short overview of the spectroscopic measurements of atomic and molecular deuterium in front of a graphite test limiter in the plasma edge of TEXTOR-94. The vibrational and rotational population of the molecules as a function of both plasma parameters and surface conditions are discussed. In contrast to deuterium gas blow experiments, in the case of recycled particles at the graphite surface, a deviation of the vibrational population from a Boltzmann distribution is found. The ratio between atomic and molecular deuterium and their behaviour due to a change of the surface condition is described. A significant change of the composition of released deuterium caused by a heating of the graphite surface is one result of these investigations. For limiter temperatures below 1100 K, the release of deuterium as a molecular species is important, and at temperatures above 1100 K, the release as atomic species starts to dominate. This result confirms the measurements on hydrogen, which were performed earlier on the same test limiter [1].