PRELIMINARY SPECTROSCOPIC EXPERIMENTS WITH HELIUM MICROWAVE-INDUCED PLASMA PRODUCED IN AIR BY USE OF A NEW STRUCTURE - THE AXIAL INJECTION TORCH

In this experimental study we have used spectroscopic methods to chara cterize helium plasma obtained by means of a novel waveguide-fed micro wave plasma torch at atmospheric pressure, the axial injection torch. This device produces a ''plasma flame'' by coupling high frequency (HF ) power at 2.45 GHz to the discharge. Various flame parameters (namely the electron density number and the electron and gas temperatures) ha ve been determined by using spectroscopic diagnostic techniques that p rovided an estimate in terms of the helium flow rate, absorbed HF powe r and axial position in the experiments. These preliminary results sug gest some departure from local thermodynamic equilibrium (LTE) and see m to indicate the utility of the discharge as an excitation source for emission spectroscopy. Comparison with other microwave torches alread y described in the literature is made in terms of the electron density and the electron and gas temperature.