INTERNAL ENERGY-DISTRIBUTIONS IN A SHIELDED PLASMA-DEVICE

A shielded plasma device has been used extensively in plasma synthesis and plasma processing. In order to optimize these processes, optical diagnostics were used to study the device operated at 545 kHz and pressures between 2.5 and 580 Torr. Plasma-induced emission for Ar, N2, and N+ 2 suggested that a local thermodynamic equilibrium point of view was inappropriate. Spatially resolved laser-induced fluorescence and laser absorption measurements were performed on the metastable argon state 3P2 and the radiative state 3P1. The metastable profiles were described in terms of a kinetic model dominated by electron-atom kinetics. The model was used to determine the electron temperature Te as a function of axial position and total gas pressure. These temperatures were found to lie in the range of 5000 K at 580 Torr to 11 000 K at 25 Torr.