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Impurity transport was investigated at both edge and core regions in large helical device(LHD) with developed spectroscopic instruments which can measure one- and two-dimensionaldistributions of impurities. The edge impurity behavior was studied recently using four carbonresonant transitions in different ionization stages of CIII (977(?)), CIV (1548(?)), CV (40.3(?)) andCVI (33.7(?)). When the line-averaged electron density, n_e, is increased from 1 to 6 × 10~(13) cm~(-3),the ratio of (CIII+CIV)/n_e increases while the ratio of (CV+CVI)/n_e decreases. Here, CIII+CIV(CV+CVI) expresses the sum of CIII (CV) and CIV (CVI) intensities. The CIII+CIV indicatesthe carbon influx and the CV+CVI indicates the emissions through the transport in the ergodiclayer. The result thus gives experimental evidence on the impurity screening by the ergodic layerin LHD, which is also supported by a three-dimensional edge particle simulation. The core impuritybehavior is also studied in high-density discharges (n_e < 1 × 10~(15) cm~(-3)) with multi H_2-pelletsinjection. It is found that the ratio of V/D (V: convection velocity, D: diffusion coefficient)decreases after pellet injection and Z_(eff) profile shows a flat one at values of 1.1～1.2. These resultsconfirm no impurity accumulation occurs in high-density discharges. As a result, the iron density,n_(Fe), is analyzed to be 6 × 10~(-7)(= n_(Fe)/n_e) of which the amount can be negligible as radiationsource even in such high-density discharges. One- and two-dimensional impurity distributionsfrom space-resolved VUV and EUV spectrometers newly developed for further impurity transportstudy are also presented with their preliminary results.
Impurity transport was investigated at both edge and core regions in large helical device (LHD) with developed spectroscopic instruments which can measure one- and two-dimensional distributions of impurities. The edge impurity behavior was found recently four carbonresonant transitions in different ionization stages of CIII (977 (?)), CIV (1548?), CV (40.3?) And CVI (33.7 (?)) When the line-averaged electron density, n_e, increased from 1 to 6 × 10 ~ (CV + CVI) / n_e decreases. Here, CIII + CIV (CV + CVI) expresses the sum of CIII (CV ) and CIV (CVI) intensities. The CIII + CIV indicatesthe carbon influx and the CV + CVI indicates the emissions through the transport in the ergodiclayer. The result then gives experimental evidence on the impurity screening by the ergodic layer in LHD, which is also supported by a three-dimensional edge particle simulation. The core impurity behavior is also studied in high-density discharge s (n_e <1 × 10 ~ (15) cm ~ (-3)) with multi H_2-pellets injection. It is found that the ratio of V / D (V: convection velocity, D: diffusion coefficient) As a result, the iron density, n_ (Fe), was analyzed to be 6 × 10 ~ (-1) -7) (= n_ (Fe) / n_e) of which the amount can be negligible as radiationsource even in such high-density discharges. One- and two-dimensional impurity distributions from space-resolved VUV and EUV spectrometers newly developed for further impurity transportstudy are also presented with their preliminary results.