Formation of double sheaths and the J-V characteristics of the obstructed region

Technical Report · Sun Jun 01 00:00:00 EDT 1980

DOI:https://doi.org/10.2172/5107580· OSTI ID:5107580

Wang, C C

The arc drop of the vapor thermionic converter is determined by the difference of sheath heights and the potential difference across the plasma. The J-V characteristics of cesium vapor diodes operating in the ignited mode show a knee corresponding to near optimum power. When the diode is operating in the region above the knee, the dominant contributor to the arc drop is the difference of the sheath heights (i.e., the potential difference across the plasma produces either a very small loss or may, in fact, reverse sign and reduce the arc drop). In this region the power decreases because the increase in output current is usually not able to compensate for the loss of output voltage. When the diode is operating in the region below the knee, the potential difference in the plasma becomes the dominant contributor to the arc drop. For these reasons, the shape of the J-V characteristics below the knee is different from that above the knee. The location of the knee is a good indicator of the maximum power and the maximum efficiency points. Under the fully optimized conditions, the knee also indicates the barrier index of the diode. Therefore, how and where the knee will appear is of great theoretical and practical interest. Some workers in the thermionic field have speculated that the appearance of the knee is due to the formation of the double sheath. However, this study indicates that the formation of the double sheath takes place significantly below the knee. In addition, this study evaluates J-V characteristics in the obstructed region.

• Research Organization: Thermo Electron Corp., Waltham, MA (USA)
• DOE Contract Number: AC02-76ET11293
• OSTI ID: 5107580
• Report Number(s): TE-4258-290-80(DRAFT)
• Country of Publication: United States
• Language: English

Related Subjects

30 DIRECT ENERGY CONVERSION
THERMIONIC CONVERTERS
ELECTRICAL PROPERTIES
PLASMA SHEATH
BOLTZMANN STATISTICS
BOUNDARY CONDITIONS
CESIUM
CURRENT DENSITY
ELECTRIC POTENTIAL
MATHEMATICAL MODELS
PLASMA
THERMIONIC DIODES
VOLTAGE DROP
ALKALI METALS
DIODE TUBES
DIRECT ENERGY CONVERTERS
ELECTRON TUBES
ELEMENTS
METALS
PHYSICAL PROPERTIES
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NESDPS Office of Nuclear Energy Space and Defense Power Systems
300401* - Thermionic Converters- Design & Development