Low-pressure electrode microwave discharge in argon and in an Ar-O2 mixture

Abstract

The phenomenological description of an electrode microwave discharge in argon and in an Ar-O2 mixture under a pressure between 1 and 30 torr and an incident power of below 300 W is presented. The results of probe measurements are reported. It is shown that the discharge can be initiated at the tip of an exiting rod antenna and takes different forms, for instance, spherical or the form of moving glowing filaments. In our case, the spatial structure of a spherical discharge is more uniform than that of discharges excited earlier in molecular gases. The addition of oxygen raises the power absorbed by the plasma (if the incident power is kept constant) and brings the discharge structure closer to that in molecular gases.