‘Fire Tube’ Formation in Expanding RF Plasma

Abstract

Multiple double layers develop during expanding capacitive mode of RF discharge in a linear vacuum vessel in the absence of external magnetic field. Dynamics of multiple double layers have been studied through electric probe diagnostics in nitrogen RF plasma operated at 13.56 MHz frequency. The burst oscillations of the potential, fire tube formations and space charge formations suggest formations of complex structures during the discharge. Our first experimental results provide interesting information about the stability of plasma sheath and space charge effect on it. The visibly bright discharge transforms into multiple intensely coaxial luminous “Fire Tube” structures on increasing the input RF power in plasma.