PLANAR CONVERTERS FOR RADIOISOTOPE GENERATORS.
Abstract
Specific tasks under this program include investigations of the feasibility of a dynamic cesium flow system (Integral Cesium Reservoir) and the development and evaluation of single-crystal tungsten emitters incorporated in planar thermionic converters. During this program an Integral Cesium Reservoir (ICR) was designed, fabricated and tested. The tests demonstrated the feasibility of the ICR and indicated that the dependence of the converter pressure on the reservoir temperature was reduced by a factor of two when the present ICR instead of a conventional reservoir was used as the cesium source in the converter. Two planar thermionic converters were constructed and tested. Both converters used single-crystal tungsten emitters of the (110) crystallographic orientation and polycrystalline molybdenum collectors with an interelectrode spacing of about 2 mils. The converters operated on a steady-state basis at an emitter temperature of 2000 K and an output voltage of 0.7 volt. One converter completed 3100 hours of continuous operation with a power density output of 21 W/sq cm for the last 2300 hours. Operation of the other converter was discontinued after 870 hours due to performance degradation. Emitter and collector work function measurements were performed periodically during operation of the converters. These measurements showed no significant variation with time of operation. The emitters used were selected from a large number of specimens subjected to different mechanical and thermal treatments designed to produce optimum surface characteristics for thermionic emission. Following these treatments, the specimens were examined in detail by optical and electron microscopy.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1967
- Accession Number
- AD0821597
Entities
People
- Laurence O. Van Someren
- Thomas Athanis