Gas phase and surface phenomena observed with a seeded plasma

This paper describes and discusses some recent experiments conducted with low-temperature seeded plasmas. The plasma was obtained by mixing potassium vapor with arc-heated argon. The experiments indicated two modes of steady, stable current conduction between the electrodes. In the first mode, the effect of gas phase phenomena predominated in fixing the current. Under certain conditions, a transition to a second mode of operation occurred. In this mode, the current was found to be thermionically limited, and was determined solely by electrode surface effects. A comparison between the observed voltage current characteristics and two current conduction theories is presented. Analysis of electrode temperature data indicated that the chief heat transfer mechanism was the penetration of the surface work function barrier as electrons entered or left the surface.