Measurement of the scrape-off layer density profile on ASDEX via an energetic neutral lithium beam

Abstract

By observation of the intensity of the collisionally excited Li resonance line along an energetic beam injected into a low-density plasma, it is possible to infer the density profile.1 On ASDEX this technique is employed to continuously measure the density profile at the plasma edge with sub-ms time resolution. The Li-beam diagnostic system is described and results presented, for a beam energy of 60 keV, which show the method to produce profiles with low statistical noise, enabling small changes in density to be followed. The inferred relative density profiles are found to be in agreement with those determined by Thomson scattering and a Langmuir probe.