Characterization of the Li-BES at ASDEX Upgrade

The lithium beam emission spectroscopy (Li-BES) is a powerful diagnostic to resolve the plasma edge density with high temporal and spatial resolution.The recent upgrades of the Li-BES at ASDEX Upgrade and the resulting gain in photon flux allow the plasma edge density to be determined with an advanced level of accuracy.Furthermore, electron density fluctuations are measured using Li-BES.The Li-BES capabilities and limitations to measure electron density profiles as well as density fluctuations are presented.Li-BES is well suited to characterize electron density turbulence in the scrape off layer (SOL) with decreasing sensitivity towards the plasma core.This is demonstrated by simulations as well as by comparisons with other diagnostics.Li-BES is an appropriate tool to study transport phenomena in the SOL over a wide range of plasma parameters due to its robustness and routine usage.