Plasma density spatial distribution control in planar helical antenna

Spatial ion density distribution is controlled by connecting an antenna in parallel with the planar helical resonator, while a capacitor was connected in series. The spatial distribution is controlled by adjusting the tap position and capacitor. Ion density is lower at the open end and higher at the ground tap. At the open end, where the voltage is maximum, a significant number of electrons escaped towards the wall. On the other hand, at the ground tap, where the voltage is minimum and the current is maximum, there is a significant amount of ionization due to the induced electric field. This results in spatial variations in density distribution.