Experimental investigation of different structures of a radio frequency produced plasma column

Experimental results on the observation of spatial structures appearing in a radio frequency (rf) produced plasma column are presented in this paper. A plasma column of length 30 cm is formed in a glass tube by applying rf power from a cw generator. It is observed that by changing the operating parameters, e.g., input power, working pressure, drive frequency, diameter of glass tube, background gases, etc., single plasma column transforms into stationary/moving striations and helical and spiral structures. For a better understanding of these observations, experiments are also carried out to study the electric field profile of these structures in the plasma. Findings of this study reveal that surface wave produced plasma column transversally bifurcates and transforms into stationary striations. With further increase in working pressure, stationary striations become moving striations with linear and rotational motions and finally rotating plasma column bifurcates longitudinally and a helical structure is for...