A 1 m vacuum ultraviolet （VUV） spectrometer with temporal and spatial resolution was developed for impurity study of HL-2A tokamak. The instrument is equipped with two concave gratings blazed at 80 nm and 150 nm, re...A 1 m vacuum ultraviolet （VUV） spectrometer with temporal and spatial resolution was developed for impurity study of HL-2A tokamak. The instrument is equipped with two concave gratings blazed at 80 nm and 150 nm, respectively, and a windowless back-illuminated charge coupled device （CCD） detector of 256 × 1024 pixels. Tile total wavelength coverage of spectrometer is 30～ 320 nm with a spectral resolution of 0.015 nm at a width of entrance slit of 10 μm. A portion of this range is observed during a plasma discharge with a spectral range of 20 nm. The minimum integration time of the detector system is about 6.7 ms for each frame in a full binning mode. Using a space-resolved slit located between the entrance slit and the grating a radial profile on the vertical direction with a range of 400 mm can be obtained. The primary results were successfully obtained with high signal-to-noise ratio and good spectral resolution, which demonstrated the instrument functions very well.展开更多
Impurity transport was investigated at both edge and core regions in large helical de- vice （LHD） with developed spectroscopic instruments which can measure one- and two-dimensional distributions of impurities. The ...Impurity transport was investigated at both edge and core regions in large helical de- vice （LHD） with developed spectroscopic instruments which can measure one- and two-dimensional distributions of impurities. The edge impurity behavior was studied recently using four carbon resonant transitions in different ionization stages of CIII （977A）, CIV （1548A）, CV （40.3A） and CVI （33.7A）. When the line-averaged electron density, ne, is increased from 1 to 6 × 10^13 cm-3, the ratio of （CIII^CIV）/ne increases while the ratio of （CV＋CVI）/ne decreases. Here, CIII^CIV （CV＋CVI） expresses the sum of CIII （CV） and CIV （CVI） intensities. The CIII＋CIV indicates the carbon influx and the CV＋CVI indicates the emissions through the transport in the ergodic layer. The result thus 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 impu- rity behavior is also studied in high-density discharges （ne 〈 1 × 10^15 cm 3） with multi H2-pellets injection. It is found that the ratio of V/D （V： convection velocity, D： diffusion coefficient） decreases after pellet injection and Zeff profile shows a flat one at values of 1.1,-1.2. These results confirm no impurity accumulation occurs in high-density discharges. As a result, the iron density, rife, is analyzed to be 6 × 10^-7（=- nFe/ne） of which the amount can be negligible as radiation source even in such high-density discharges. One- and two-dimensional impurity distributions from space-resolved VUV and EUV spectrometers newly developed for further impurity transport study are also presented with their preliminary results.展开更多
基金National Natural Science Foundation of China(No.10475022)
文摘A 1 m vacuum ultraviolet （VUV） spectrometer with temporal and spatial resolution was developed for impurity study of HL-2A tokamak. The instrument is equipped with two concave gratings blazed at 80 nm and 150 nm, respectively, and a windowless back-illuminated charge coupled device （CCD） detector of 256 × 1024 pixels. Tile total wavelength coverage of spectrometer is 30～ 320 nm with a spectral resolution of 0.015 nm at a width of entrance slit of 10 μm. A portion of this range is observed during a plasma discharge with a spectral range of 20 nm. The minimum integration time of the detector system is about 6.7 ms for each frame in a full binning mode. Using a space-resolved slit located between the entrance slit and the grating a radial profile on the vertical direction with a range of 400 mm can be obtained. The primary results were successfully obtained with high signal-to-noise ratio and good spectral resolution, which demonstrated the instrument functions very well.
基金the LHD project (NIFS08ULPP527)the JSPS-CAS Core-University program in the field of Plasma and Nuclear Fusion
文摘Impurity transport was investigated at both edge and core regions in large helical de- vice （LHD） with developed spectroscopic instruments which can measure one- and two-dimensional distributions of impurities. The edge impurity behavior was studied recently using four carbon resonant transitions in different ionization stages of CIII （977A）, CIV （1548A）, CV （40.3A） and CVI （33.7A）. When the line-averaged electron density, ne, is increased from 1 to 6 × 10^13 cm-3, the ratio of （CIII^CIV）/ne increases while the ratio of （CV＋CVI）/ne decreases. Here, CIII^CIV （CV＋CVI） expresses the sum of CIII （CV） and CIV （CVI） intensities. The CIII＋CIV indicates the carbon influx and the CV＋CVI indicates the emissions through the transport in the ergodic layer. The result thus 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 impu- rity behavior is also studied in high-density discharges （ne 〈 1 × 10^15 cm 3） with multi H2-pellets injection. It is found that the ratio of V/D （V： convection velocity, D： diffusion coefficient） decreases after pellet injection and Zeff profile shows a flat one at values of 1.1,-1.2. These results confirm no impurity accumulation occurs in high-density discharges. As a result, the iron density, rife, is analyzed to be 6 × 10^-7（=- nFe/ne） of which the amount can be negligible as radiation source even in such high-density discharges. One- and two-dimensional impurity distributions from space-resolved VUV and EUV spectrometers newly developed for further impurity transport study are also presented with their preliminary results.
