Spectroscopic Studies on Impurity Transport of Core and Edge Plasmas in LHD

摘要

Spectroscopic diagnostics have been extensively developed for studies of impurityand neutral particle transports at core and edge plasmas in LHD.Diagnostics of core plasmas aresimilar to a tokamak case,i.e.,Z_(eff)from visible bremsstrahlung,K-x-ray measurements from x-ray spectroscopy using Si(Li)detectors and a compact crystal spectrometer,and high-Z impuritydiagnostics from VUV spectroscopy using a flat-field EUV spectrometer.A combination of impu-rity pellet injection and visible bremsstrahlung is an active tool for determination of the diffusioncoefficient D and convective velocity V.Using this tool the spatial structures of D and V areobtained and discussed with a neoclassical effect.On the other hand,the spectroscopic methodfor edge diagnostics is considerably different from the tokamak case because of the existence of athick ergodic layer in addition to the x-points necessarily included into the diagnostic chord view.In order to break this negative situation,Zeeman and polarization spectroscopy are adopted toLHD edge plasmas.As a result,2-dimensional emission contours of HeI and H_α are successfullyobtained.Laser absorption spectroscopy is tried to measure hydrogen neutrals directly.Radialprofiles of edge impurities are also measured with a mirror-assembled 3 m VUV spectrometer.Recent results of and progress in LHD spectroscopy are briefly reviewed.