Plasma parameters of a small microwave discharge at atmospheric pressure obtained by probe diagnostics

We present the design of a system for probe diagnostics and the results obtained for the plasma parameters in a small portable microwave plasma source operating at atmospheric pressure. The average electron temperature and the argon plasma density in the discharge are estimated from the current-voltage (I-V) characteristics of an asymmetric double probe. The calculated value of the electron temperature is T-e similar to 1.7 +/- 0.3 eV. Three models for the probe ion saturation current in a flowing plasma at atmospheric pressure are applied to calculating the plasma density. The calculated value of the plasma density varies with the input power P = 15 - 25 W and gas flow rate 250 - 350 sccm. The plasma density estimations obtained by the models lie within a wide range and are compared with results from optical diagnostics.