Explorative studies for the development of fast He beam plasma diagnostics

Modelling calculations for a fast He beam on its way through a tokamak plasma have been performed at TU Wien. They are based on the collisional-radiative ADAS model for He beams which delivers radially resolved population density and line intensity profiles for any initial population of a diagnostic He beam and any plasma structure. The effect of the metastable triplet population in the incident beam on the line emission profiles is shown. A sensitivity study of the optical lines with respect to electron temperature and density has been performed in the plasma edge and core regions. To validate these model calculations, experiments using fast He beams and beam emission spectroscopy have been performed at ASDEX Upgrade (IPP Garching) and JET by injecting He gas into the ion sources of the H- or D-heating beam systems.