A normal incidence vacuum ultraviolet (VUV) and a grazing incidence extreme ultraviolet (EUV) spectrometers have been developed for the edge and core impurity measure- ments in HL-2A tokamak. The VUV and the EUV s...A normal incidence vacuum ultraviolet (VUV) and a grazing incidence extreme ultraviolet (EUV) spectrometers have been developed for the edge and core impurity measure- ments in HL-2A tokamak. The VUV and the EUV spectrometers cover wavelength ranges of 300-3200 A and 50-500A, respectively. A spatial resolution of 2 mm has been achieved for the VUV spectrometer when a space-resolved slit 50 #m in width is used. The space-resolved slit is placed between the entrance slit and the grating of the spectrometer. The spectral resolutions of 0.15/~ for the VUV spectrometer in the wavelength coverage of the concave 1200 grooves/mm grating and of 0.22A for the EUV spectrometer at λ=200A with a flat-field laminar-type holo- graphic grating are obtained. The sensitivity of the VUV spectrometer was calibrated in situ with the plasma bremsstrahlung radiation. The experimental results from both spectrometers are presented, especially the line intensity radial profiles measured by the VUV spectrometer.展开更多
Neon glow discharge cleaning was firstly attempted in Large Helical Device(LHD) instead of He glow discharge to remove hydrogen neutrals and to control the ion density, n_i.The Ne glow discharge continued for 8 hours ...Neon glow discharge cleaning was firstly attempted in Large Helical Device(LHD) instead of He glow discharge to remove hydrogen neutrals and to control the ion density, n_i.The Ne glow discharge continued for 8 hours overnight after a three-day experiment. At the secondnight H_α emission became weaker than the emission usually observed in the He glow discharge. Aclear reduction of the hydrogen influx was also observed in neutral beam injection (NBI) dischargeswith Ne puff, whereas the neon recycling was strongly enhanced with appearance of a flat densityprofile. As a result, the lowest density limit was further reduced down to 0.2 X 10^(13)cm^(-3). Theuse of Ar puff formed a peaked density profile with a high T_i of 7 keV.展开更多
A repetitive pellet injector has been developed for investigation ofrefueling issues towards the steady-state operation in Large Helical Device (LHD). Continuousoperation of more than 10000 pellet launching at 10 Hz h...A repetitive pellet injector has been developed for investigation ofrefueling issues towards the steady-state operation in Large Helical Device (LHD). Continuousoperation of more than 10000 pellet launching at 10 Hz has been demonstrated. The maximum repeatingrate is 11 Hz. No technical constraint for longer operation has been found. The reliability ofpellet launch has exceeded 99.9%. The initial application to the NBI-heated plasmas has beensuccessful in the last experimental campaign of LHD. Although the pulse length is limited by theoperational constraint of NBI, the plasma with a density of 8 X 10^(19) m^(-3) has been sustainedfor 2 s by the pellet injection at 10 Hz. A prospect for the future experiment is discussed on thebasis of the initial result.展开更多
A space-resolved EUV spectrometer for measuring the one-dimensional distribution of impurity line emissions in Large Helical Device (LHD) has been upgraded to measure two- dimensional distributions of impurity line ...A space-resolved EUV spectrometer for measuring the one-dimensional distribution of impurity line emissions in Large Helical Device (LHD) has been upgraded to measure two- dimensional distributions of impurity line emissions with an extension of working wavelength range to 30-650% The two-dimensional measurement is performed by scanning the observation chord horizontally. A rectangular plasma region of 520 × 700 mm2 in vertical and horizontal sizes can be observed during a single horizontal scan. The horizontal scan requires a time duration of 5 s at least. The spatial resolution is 10 mm in the vertical direction when a spatial-resolution slit of 0.2 mm in width is adopted. Although a spatial resolution in the toroidal direction is 75 mm, it is a function of CCD exposure time and horizontal scanning speed. Two-dimensional distribution of EUV line emissions from several impurities has been successfully observed for the first time from steady discharges in LHD. In this paper two-dimensional distributions of He II (303.78A), C V (40.27A), C VI (33.73A) and Fe XX (132.85A) located at different radial positions are presented with simple analysis on the magnetic field structure of LHD.展开更多
基金partially supported by National Natural Science Foundation of China (Nos. 10975048 and 11175061)the JSPS-NRF-NSFC A3 Foresight Program in the Field of Plasma Physics (No. 11261140328)
文摘A normal incidence vacuum ultraviolet (VUV) and a grazing incidence extreme ultraviolet (EUV) spectrometers have been developed for the edge and core impurity measure- ments in HL-2A tokamak. The VUV and the EUV spectrometers cover wavelength ranges of 300-3200 A and 50-500A, respectively. A spatial resolution of 2 mm has been achieved for the VUV spectrometer when a space-resolved slit 50 #m in width is used. The space-resolved slit is placed between the entrance slit and the grating of the spectrometer. The spectral resolutions of 0.15/~ for the VUV spectrometer in the wavelength coverage of the concave 1200 grooves/mm grating and of 0.22A for the EUV spectrometer at λ=200A with a flat-field laminar-type holo- graphic grating are obtained. The sensitivity of the VUV spectrometer was calibrated in situ with the plasma bremsstrahlung radiation. The experimental results from both spectrometers are presented, especially the line intensity radial profiles measured by the VUV spectrometer.
文摘Neon glow discharge cleaning was firstly attempted in Large Helical Device(LHD) instead of He glow discharge to remove hydrogen neutrals and to control the ion density, n_i.The Ne glow discharge continued for 8 hours overnight after a three-day experiment. At the secondnight H_α emission became weaker than the emission usually observed in the He glow discharge. Aclear reduction of the hydrogen influx was also observed in neutral beam injection (NBI) dischargeswith Ne puff, whereas the neon recycling was strongly enhanced with appearance of a flat densityprofile. As a result, the lowest density limit was further reduced down to 0.2 X 10^(13)cm^(-3). Theuse of Ar puff formed a peaked density profile with a high T_i of 7 keV.
文摘A repetitive pellet injector has been developed for investigation ofrefueling issues towards the steady-state operation in Large Helical Device (LHD). Continuousoperation of more than 10000 pellet launching at 10 Hz has been demonstrated. The maximum repeatingrate is 11 Hz. No technical constraint for longer operation has been found. The reliability ofpellet launch has exceeded 99.9%. The initial application to the NBI-heated plasmas has beensuccessful in the last experimental campaign of LHD. Although the pulse length is limited by theoperational constraint of NBI, the plasma with a density of 8 X 10^(19) m^(-3) has been sustainedfor 2 s by the pellet injection at 10 Hz. A prospect for the future experiment is discussed on thebasis of the initial result.
基金partially carried out under the LHD project financial support (NIFS12ULPP010)partly supported by the JSPS-NRF-NSFC A3 Foresight Program in the field of Plasma Physics (No. 11261140328)
文摘A space-resolved EUV spectrometer for measuring the one-dimensional distribution of impurity line emissions in Large Helical Device (LHD) has been upgraded to measure two- dimensional distributions of impurity line emissions with an extension of working wavelength range to 30-650% The two-dimensional measurement is performed by scanning the observation chord horizontally. A rectangular plasma region of 520 × 700 mm2 in vertical and horizontal sizes can be observed during a single horizontal scan. The horizontal scan requires a time duration of 5 s at least. The spatial resolution is 10 mm in the vertical direction when a spatial-resolution slit of 0.2 mm in width is adopted. Although a spatial resolution in the toroidal direction is 75 mm, it is a function of CCD exposure time and horizontal scanning speed. Two-dimensional distribution of EUV line emissions from several impurities has been successfully observed for the first time from steady discharges in LHD. In this paper two-dimensional distributions of He II (303.78A), C V (40.27A), C VI (33.73A) and Fe XX (132.85A) located at different radial positions are presented with simple analysis on the magnetic field structure of LHD.