Diagnostics Based on Helium Neutral Beams in Iter

Abstract

Reducing the activation of the vessel and its components during the early phase of ITER operation is important. One scheme of minimising the activation is to use helium as the heating neutral beam species. This gives rise to a concern about how effective diagnostic spectroscopy will be with such beams. The diagnostic use of deuterium heating beams is well established yielding, for example, ion temperature profiles, plasma rotation, magnetic fields, impurity concentration, Z_eff and beam penetration measurements. The experience with helium beams is more limited and there are greater uncertainties in the fundamental atomic data. A helium neutral beam has certain potential advantages: a reduced beam halo, no fractional energy components, greater penetration than deuterium beams and possibly more efficient charge exchange donation in certain energy regions.