True Asymptotic Plasma-Sheath Matching with an Asymptotically Correct Collisional Presheath
Abstract
The work on plasma presheaths, which form a transition region between the collisionless electrode sheaths and the plasma, is directed toward the problems of the Thermionic Energy Converter (TEC). A schematic of a TEC is shown in a reactor core for space power applications and the basic physics, Cesium is put the gap between the emitter and collector for two purposes: First, to ionize and neutralize the space charge so that a useful electron current density can pass (10 - 100 amps/square cm), and second to reduce the electrode work functions by adsorption fo cesium. Of the plasma physics of the cesium filled gap of the TEC, the plasma-electrode interactions are the most significant part because these regions form boundary conditions which control the plasma density and temperatures of the entire gap. Thus the research under this grant has been directed toward the study of collisional presheaths which form the layer adjacent to an electrode on the order of one ion mean free path thick. However, the research pursued under this grant is not limited in applicability to TECs but is on interest to plasma-surface interactions in general. Other applications include electric propulsion where electrode erosion is a problem and not fully understood and more generally any plasma-surface interaction. This report included the asymptotic presheath theory developed, and is preceded by the basic theory of the Thermionic Energy Converter (TEC) and is followed by the application of the theory to a time dependent model of the TEC in the program called TEC. As shown in the TEC results, the agreement with experiment is good except in the low current regime of the TEC where an unexplained disagreement remains. This is still a puzzle.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 30, 1989
- Accession Number
- ADA212857
Entities
People
- Geoffrey L. Main
Organizations
- Georgia Tech