PLASMA PROPERTIES IN A THERMIONIC CONVERTER.
Abstract
The properties of the non-equilibrium plasma existing in the interelectrode space of the arc-mode converter were investigated with coaxial electrostatic Langmuir probes. Probe measurements were made as a function of cesium pressure, emitter temperature, interelectrode position and converter output in several low-temperature arc-mode converters. The plasma potential, was found to vary significantly across the interelectrode space. Both the existence of a retarding sheath for electrons very close to the emitter surface and a region farther from the emitter in which the variation in plasma potential is accelerating for electrons have been detected. Significant variations in the plasma potential existing in the space were observed with changes in emitter temperature, cesium pressure, and converter output. The electron energy distribution is non-Maxwellian with a significant number of electrons with energies in excess of 1.4 eV. However, from an analysis of the production and loss rates in the converter, there is an insufficient number of electrons, even in the accelerated electron energy distribution, to account for the enhanced degree of ionization observed in arc-mode operation by single stage electron-atom collisional ionization processes. Further analyses of the production and loss rates using the electron energy distribution indicate that ambipolar diffusion is the dominant loss process in the converter if the major ionic species is Cs(+). However, if the major ionic species in the converter is Cs sub 2(+), then recombination is the dominant loss mechanism. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 25, 1964
- Accession Number
- AD0600096
Entities
People
- R. H. Bullis
- W. J. Wiegand
Organizations
- United Aircraft Corporation