Plasma edge diagnostics by atomic beam supported emission spectroscopy-status and perspectives

TLDR

Atomic beam supported emission spectroscopy offers high space‑ and time resolution with minimal plasma perturbation, and its potential to address plasma turbulence and the two‑dimensional character of the edge depends on further technical development. Using Li, He, and H atomic beams of varying velocities, the technique measures electron density, electron and ion temperature, and radial impurity profiles, with the atom sources described for the TEXTOR tokamak. Recent TEXTOR experiments measured these plasma parameters and the results are presented and critically discussed.

Abstract

Atomic beam supported emission spectroscopy is well suited to satisfy the needs of edge diagnostics; in particular, it offers high space- and time resolution and causes almost no perturbation of the plasma. Making use of the species Li, He and H. atomic beams have been developed, in different velocity ranges, by the help of which the most important plasma parameters can be measured. The principles for the measurement of the electron density and temperature profiles of the ion temperature profile and of the radial profiles of highly ionized impurities are explained and the atom sources used at TEXTOR are described. Recent results obtained on TEXTOR for various plasma parameters are presented and critically discussed. We are convinced that plasma turbulence and the two-dimensional character of the plasma edge will be important challenges for the future. Atomic beams may offer solutions only if sufficient efforts are invested into their technical development.