Effect of the RF wall conditioning on the high performance plasmas in the Large Helical Device

Current Status of Large Helical Device and Its Prospect for Deuterium Experiment

“…Figure 2(a) shows the typical ion temperature profile, electron temperature profile, and electron density profile at the high ion-temperature discharge on LHD where central ion temperature of 8.1keV at 1x10 19 m -3 was achieved. 7,8 As shown in the figure, an internal transport barrier with steep ion temperature gradient is formed in the region between r eff =0.2 and 0.4m in this discharge. It was found that the "impurity hole," where most of the impurity ions were expelled from the core region of plasmas, was formed in the high ion temperature plasmas on LHD.…”

“…Additional heating by ECH of 3MW is also assumed. In evaluating the emission rate, a model density profile of (1-(r/a) 8 ) and a model temperature profile of (1-(r/a) 2 ) 2 are used. The electron temperature and density is assumed to be equal to the ion temperature and density, respectively.…”

Comparison of Ion Internal Transport Barrier Formation between Hydrogen and Helium Dominated Plasmas

“…In order to replace the gas species, intense discharge cleaning was carried out before the experiment. The long pulse helium discharges with the duration time of 60 sec were repeated with ion cyclotron range of frequency (ICRF) heating [6][7][8]. The hydrogen recycling was reduced significantly.…”

Radiation control in LHD and radiation shielding capability of the torus hall during first campaign of deuterium experiment

“…The goals of the LHD project are to achieve high temperature plasma, high density plasma and high beta plasma, and to reveal the physics in these high-performance plasmas [2]. For these goals, LHD has been upgraded so far with installing heating systems, higher power supply systems, and the components for improved plasma confinement [3][4][5][6][7][8]. On the other hand, it has been experimentally confirmed by the plasma experiments in other fusion devices that the use of deuterium plasma can improve the plasma performance [9][10][11].…”