Behavior of thermal electropositive plasma near electron emitting surfaces

Abstract

This study investigates the behavior of a thermal plasma sheath comprising positive ions as well as primary electrons in contact with electron-emitting surfaces. The Bohm sheath criterion is found to depend on the parameter of nonextensivity, the temperature ratio of positive ions to primary electrons, the secondary electron emission coefficients for primary electrons and positive ions, as well as the floating potential. Considering both thermal and cold plasma cases with superextensive ( q < 1) and extensive (Maxwellian, q = 1) primary electron distributions, the influence of positive ion temperature on sheath properties is numerically examined using the Bohm sheath criterion and the wall potential. A comparative study is also conducted between the results with and without secondary electron emission. Furthermore, it is found that for high-energy primary electrons (superextensive plasma), the presence of secondary electron emission significantly reduces the sheath thickness compared to that in a Maxwellian plasma. This work provides significant insights into plasma- surface interactions which have potential applications in plasma processing technologies and magnetic confinement fusion devices, contributing to the advancement of efficient energy systems.