EMISSION-SPECTROSCOPY DIAGNOSTICS OF A DC PLASMA-JET DIAMOND REACTOR

We performed emission spectroscopy on a d.c. plasma jet (Ar, H-2, CH4) chemical vapor deposition reactor. We used a spectrometer with a larg e spectral range (150-800 nm), a spectral resolution of 0.07 nm and a spatial resolution better than 1 mm. We were able to derive informatio n concerning the gaseous species existing in the plasma (CH, C-2, H, A r, C) as well as their evolution with torch parameters. Studies of the CH (B-2 Sigma --> X(2) Pi) rotational band and the C-2 (A(3) Pi(g) -- > X(3) Pi(u)) rovibrational bands allowed temperature measurements usi ng both spectra simulation and the Boltzmann method. We thus obtained rotational temperature maps of the jet and information on the vibratio nal temperature. These data will be useful for modelling the plasma je t. Emission spectroscopy also provides information concerning the elec tron densities in the plasma. Indeed, significantly Stark broadened H Balmer lines were observed.