Gas fueling effect on plasma profile in Heliotron J

The optimization of gas fueling scenarios has been studied to improve the plasma performance in Heliotron J. Gas fueling effects on the plasma profile are discussed by comparing two fueling methods, a short pulse H2-beam fueling with a supersonic molecular-beam injection (SMBI) technique and a high intensity gas-puff fueling (HIGP) with a conventional gas puff technique. The maximum plasma stored energy Wp after SMBI is about 20% higher than that after HIGP in this NBI-only sustained plasma experiment, where the line-averaged density is almost the same (∼3 × 1019 m−3) for both cases. The electron and ion temperatures in the SMBI case are higher than those are in the HIGP case at the Wp-peak timing. A peaked density profile is observed after SMBI, while it is flat or slightly hollow for the case of HIGP. These observations point out the importance of SMBI fueling for plasma density control to obtain better plasma performance.