The TEXT neutral lithium beam edge density diagnostic

A fast neutral lithium beam has been installed on the TEXT tokamak for beam emission spectroscopy studies of the edge plasma electron-density profile. The diagnostic was recently upgraded from ten to twenty spatial channels, each of which has two detectors, one to measure lithium beam signal and one to monitor plasma background light. The spatial resolution is 6 mm, and the temporal resolution is designed to be as high as 10 ms for studies of transient events including plasma density fluctuations. Initial results are presented from the ten-channel system: Edge electron densities unfolded from the LiI (2 s 2S--2 p 2P) 670.8 nm emission profile have the same general time dependence as the line-averaged density measured by microwave interferometry