THE SURFACE IONIZATION AND VOLUME IONIZATION MODES OF OPERATION IN THE THERMIONIC PLASMA ENERGY CONVERTER

Journal Article · Sun Jul 01 04:00:00 EDT 1962 · Advan. Energy Conversion

OSTI ID:4729326

Talaat, M E

The plasma diffusion equations for electrons and ions, Poisson's equation, the continuity equations, and the proportionality assumption are examined and solutions are obtained for two cases: (1) when the ions are primarily produced at the emitter electrode surface, and (2) when important volume ionization exists in the interelectrode space. These solutions are then used to examine typical examples of the two modes of operation of the thermionic plasma energy converter. One, the surface ionization mode of operation, is characterized by an output current density that represents a fraction of the Richardson saturation current density and the second mode, the volume ionization mode of operation, is characterized by an output current density approximately an order of magnitude higher than the surface ionization current density. It is shown that for the surface ionization mode of operation the current density at maximum power is proportional to the electron density at the emitter sheath edge, is proportional to the mean free path of the electron, and is inversely proportional to the interelectrode spacing. When the electron temperature is raised by going toward short circuit conditions, high volume ionization takes place and a new stable operating region may be reached when the electron temperature is such that the generated ion density in the interelectrode space gives rise to a high electric field epsilon at the emitter surface (due to the plasma ions reaching the emitter surface from the plasma region). The high volume ionization mode of operation is maintained as long as the energy balance equation is satisfied at the high electron temperatures necessary for maintaining the high plasma ion current density collected by the emitter electrode. The plasma ion current density reaches, in typical examples, values which are three orders of magnitude greater than the typical ion current density generated by surface ionization (the SahaLangmuir equation). The latter current density is symptomatic of the surface ionization mode of operation. The transition from volume ionization mode to surface ionization mode is reached when the electron temperature necessary for adequate volume ionization does not satisfy the energy balance equation. (auth)

• Research Organization: Martin Marietta Corp., Baltimore
• NSA Number: NSA-17-020615
• OSTI ID: 4729326
• Journal Information: Advan. Energy Conversion, Journal Name: Advan. Energy Conversion Vol. Vol: 2
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

CIRCUITS
CONTINUITY EQUATIONS
CONVERSION
CURRENTS
DENSITY
DIFFERENTIAL EQUATIONS
DIFFUSION
DIFFUSION LENGTH
DISTANCE
ELECTRIC FIELDS
ELECTRODES
ELECTRON TEMPERATURE
ELECTRONS
EMISSION
ENERGY
EQUATIONS
IONIZATION
IONS
OPERATION
PHYSICS
PLASMA
POISSON EQUATIONS
POWER
RICHARDSON EQUATION
SAHA-LANGMUIR EQUATION
STABILITY
SURFACES
TEMPERATURE
THERMIONICS
TRANSIENTS
VOLUME