Fusion Science and Technology / Volume 51 / Number 2T / February 2007 / Pages 86-88
Technical Paper / Open Magnetic Systems for Plasma Confinement
One of the peculiar characteristics of the HANBIT discharge is that plasma density varies as stepwise manner on applied RF power and there does not exist stable discharge between the each of steps.
We believe that the plasma density is determined as the balance of loss power caused by transport and absorbed power coupled with radio frequency antenna. According to previous simulation concerning RF wave coupling with the plasma, the antenna loading impedance or the plasma resistance is very peaky on the plasma density variation. It implies that the plasma impedance at the density at which the power is balanced is not continuous on applied RF power. Even though the plasma resistance is very sensitive to the plasma conditions of density and external magnetic field and have peaky dependence on plasma conditions, up to now we have used fixed RF matching condition and successfully implemented discharge experiments. To investigate the characteristics of density variation on applied RF power and reason how does the impedance well adjust to separated discharge conditions, we performed self-consistent discharge simulation. The results well explain the behavior of the plasma density on applied RF power and the reason why we can use fixed matching condition for various plasma conditions.