The results on high power injection with the ueutral bean, injection （NBI） system for the Large Helical Device （LHD） are reported. The system consists of three beam-lines with two hydrogen negative ion （H^- ion）...The results on high power injection with the ueutral bean, injection （NBI） system for the Large Helical Device （LHD） are reported. The system consists of three beam-lines with two hydrogen negative ion （H^- ion） sources installed in each beam-line. In order to improve the injection power, a new beam accelerator with a multi-slot grounded grid （MSGG） has been developed and applied to one beam-line. Using the accelerator, a maximum power of 5.7 MW was achieved in 2003 and 2004, and the maximum energy of 189 keV was reached. The power and energy exceeded the design values of the individual beam-line for LHD. The other beam-lines also increased their injection power up to about 4 MW, and the total injection power of 13.1 MW was achieved with three beam-llnes in 2003. Although the accelerator had an advantage in high power beam injection, extracted beams expand in the short side direction of the ground-grid slot. The disadvantage has been resolved by modifying the aperture shapes of the steering grid.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
基金supported in part by the JSPS-CAS Core-University Program in the field of Plasma and Nuclear Fusion
文摘The results on high power injection with the ueutral bean, injection （NBI） system for the Large Helical Device （LHD） are reported. The system consists of three beam-lines with two hydrogen negative ion （H^- ion） sources installed in each beam-line. In order to improve the injection power, a new beam accelerator with a multi-slot grounded grid （MSGG） has been developed and applied to one beam-line. Using the accelerator, a maximum power of 5.7 MW was achieved in 2003 and 2004, and the maximum energy of 189 keV was reached. The power and energy exceeded the design values of the individual beam-line for LHD. The other beam-lines also increased their injection power up to about 4 MW, and the total injection power of 13.1 MW was achieved with three beam-llnes in 2003. Although the accelerator had an advantage in high power beam injection, extracted beams expand in the short side direction of the ground-grid slot. The disadvantage has been resolved by modifying the aperture shapes of the steering grid.
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.
