Experimental Investigation of Gas Phase and Surface Phenomena in a Seeded Plasma

Citation

Pinchak, Alfred Cyril (1963) Experimental Investigation of Gas Phase and Surface Phenomena in a Seeded Plasma. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/951D-2728. https://resolver.caltech.edu/CaltechTHESIS:05182011-164000438

Abstract

This thesis deals with some recent experiments conducted with low-temperature seeded plasmas at atmospheric pressure. A simple arc jet was utilized to heat a steady flow of argon gas which was subsequently mixed with a small amount of potassium vapor. The resulting mixture was then channeled through a suitable electrode configuration. Results of the experiments indicated two modes of steady, stable current conduction between the electrodes. The data indicated that thermionic emission was sufficient to provide the observed currents during both modes of operation. In the first, or normal, 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 thus was determined solely by electrode surface effects. A quantitative comparison between the observed voltage-current characteristics and two current conduction theories is presented. The aforementioned comparison, along with a quantitative examination of the experimentally observed elevated electron temperatures, indicated that both Joule heating and some non-equilibrium process must be considered in order to obtain a satisfactory understanding of the current conduction phenomena. Electrode heat transfer was studied by observing variation of the electrode temperatures with magnitude and polarity of the current. Analysis of the data indicated that an important heat transfer mechanism was the penetration of the surface work function barrier as electrons entered or left the surface.

Thesis Files