A heavy ion beam probe （HIBP） using a 3-MV tandem accelerator has been installed on large helical device （LHD）. Electrostatic potential in core plasma can be measured under the toroidal magnetic field strength of ...A heavy ion beam probe （HIBP） using a 3-MV tandem accelerator has been installed on large helical device （LHD）. Electrostatic potential in core plasma can be measured under the toroidal magnetic field strength of up to 3 T. By using the HIBP, the transition of potential profiles from electron-root to ion^root is observed in core plasmas during ramp-up of the electron density. Potential fluctuations are also measured electron cyclotron current drive （ECCD）. Two kind of characteristic fluctuations are observed. One is a reversed-shear-induced Alfv^n eigenmode （RSAE）, whose frequency varies during the evolution of the rotational transform profile, and the other is with a constant geodeisc acoustic mode （GAM） frequency.展开更多
A cylindrical carbon pellet with a size of 1.2L x 1.2φ mm to 1.8L x 1.8φ mm and a velocity of 100 m/s to 300 m/s was injected into large helical device （LHD） for an efficient fueling based on its deeper deposition...A cylindrical carbon pellet with a size of 1.2L x 1.2φ mm to 1.8L x 1.8φ mm and a velocity of 100 m/s to 300 m/s was injected into large helical device （LHD） for an efficient fueling based on its deeper deposition instead of hydrogen gas puffing and ice pellet injection. Electron density increment of Ane = 10^14 cm^-3 is successfully obtained by single carbon pellet injection without plasma collapse. Typical density and temperature of the ablation plasma of the carbon pellet, e.g., 6.5× 10^16 cm^-3 and 2.5 eV for CII, are examined respectively by spectroscopic method. A confinement improvement up to 50% compared to ISS-95 stellarator scaling is clearly observed in a relatively low-density regime of ne = 2 × 10^13 cm^-3 to 4×10^13 cm^-3, and high ion temperature Ti（0） of about 6 keV is also observed with an internal transport barrier at ne = 1.2 × 10^13 cm^-3. In particular, the improvement in the ion temperature largely exceeds that observed in hydrogen gas-puffed discharges, which typically ranges below 3 keV.展开更多
基金MEXT Japan under Grant-in-Aid for Young Scientists (Nos.16760674,18760640)the JSPS-CAS Core-University program in the field of Plasma and Nuclear FusionNIFS/NINS under the project of Formation of International Network for Scientific Collaborations and NIFS07ULBB505
文摘A heavy ion beam probe （HIBP） using a 3-MV tandem accelerator has been installed on large helical device （LHD）. Electrostatic potential in core plasma can be measured under the toroidal magnetic field strength of up to 3 T. By using the HIBP, the transition of potential profiles from electron-root to ion^root is observed in core plasmas during ramp-up of the electron density. Potential fluctuations are also measured electron cyclotron current drive （ECCD）. Two kind of characteristic fluctuations are observed. One is a reversed-shear-induced Alfv^n eigenmode （RSAE）, whose frequency varies during the evolution of the rotational transform profile, and the other is with a constant geodeisc acoustic mode （GAM） frequency.
文摘A cylindrical carbon pellet with a size of 1.2L x 1.2φ mm to 1.8L x 1.8φ mm and a velocity of 100 m/s to 300 m/s was injected into large helical device （LHD） for an efficient fueling based on its deeper deposition instead of hydrogen gas puffing and ice pellet injection. Electron density increment of Ane = 10^14 cm^-3 is successfully obtained by single carbon pellet injection without plasma collapse. Typical density and temperature of the ablation plasma of the carbon pellet, e.g., 6.5× 10^16 cm^-3 and 2.5 eV for CII, are examined respectively by spectroscopic method. A confinement improvement up to 50% compared to ISS-95 stellarator scaling is clearly observed in a relatively low-density regime of ne = 2 × 10^13 cm^-3 to 4×10^13 cm^-3, and high ion temperature Ti（0） of about 6 keV is also observed with an internal transport barrier at ne = 1.2 × 10^13 cm^-3. In particular, the improvement in the ion temperature largely exceeds that observed in hydrogen gas-puffed discharges, which typically ranges below 3 keV.
