Spectroscopic diagnostics for spatial density distribution of plasmoid by pellet injection in Large Helical Device

摘要

In order to investigate the behavior of the plasmoid which is the pellet ablatant ionized by background plasma, two-dimensional imaging measurements of high-speed spectroscopy using a fast camera has been developed in the Large Helical Device. The diagnostic system provides the density distribution of the plasmoid. The density distribution is determined by the Stark broadening width of Balmer-β line. The Stark broadening profile can be evaluated from the intensity ratio measured with narrow-band optical filters having different full width at half maximum. The two-dimensional images of the plasmoid by the fast camera connected to a bifurcated fiber scope with two objective lenses are obtained. As an initial result from the imaging measurements, it is shown that the plasmoid density is in the order of 1023 m-3.