Sheath Oscillations During Fire Tube Formation In Expanding Rf Plasma

This paper is devoted to the temporal study of the sheath dynamics during "Fire Tube" formations in expanding radio frequency plasma source, using electric and magnetic probe diagnostics. Although plasma discharges using additional electrodes immersed in plasma have been extensively investigated in DC plasmas, present work exhibits features that make it unique in terms of complex sheath structure formations, sheath oscillations and significant presence of non-thermal electrons during the expanding radio frequency (RF) discharge. The burst oscillations of the potential occur due to the oscillations of the electric field associated with the high-gradient plasma source geometry, the sheath field. The luminous discharge transforms into multiple coaxial "Fire Tube" structures with progressive RF power in plasma.