Transition radiation energy loss in inductively coupled argon plasma

This work studies the transition radiation energy loss in inductively coupled argon plasma. Energy loss channels due to ionization, momentum transfer, and radiation are investigated in argon plasma bounded by a cylindrical metal vessel. Radiation energy is calculated using the electron energy distribution function diagnosed by a Langmuir probe and the emission cross section. The measured electron energy is found to feature a Druyvesteyn-like distribution. Detailed emission lines and their relative intensity are investigated using high resolution optical emission spectroscopy. Radiation energy loss due to the blue lines (mainly 5p -> 4s transition) and red-IR lines (4p -> 4s transition) appears less prominent than that of the two ultraviolet emission lines originated from the transitions of the two lowest resonant levels to the ground state. Approximately 30% collisional energy loss is responsible for ionization, whereas only a few percent of the energy loss is attributed to elastic collision. Most energy loss is due to the transition radiation emission. These findings are remarkably important for controllable plasma aided materials processing.