Close-spaced thermionic converters with active spacing control and heat-pipe isothermal emitters

Book · Tue Dec 31 04:00:00 EST 1996

OSTI ID:442761

Fitzpatrick, G O; Koester, J K; Chang, J; Britt, E J; McVey, J B ^[1]

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1. Space Power, Inc., San Jose, CA (United States)

Thermionic converters with interelectrode gaps smaller than 10 microns are capable of substantial performance improvements over conventional ignited mode diodes. Previous devices which have demonstrated operation at such small gaps have done so at low power densities and emitter temperatures. Higher power operation requires overcoming two primary design issues: thermal distortion of the emitter due to temperature gradients and degradation of the in-gap spacers at higher emitter temperatures. This work describes two innovations for solution of these issues. The issue of thermal distortion was addressed by an isothermal emitter incorporating a heat-pipe into its structure. Such a heat-pipe emitter, with a single-crystal emitting surface, was fabricated and characterized. Finite-element computational modeling was used to analyze its distortion with an applied heat flux. The calculations suggested that thermal distortion would be significantly reduced as compared with a solid emitter. Ongoing work and preliminary experimental results are described for a system of active interelectrode gap control. In the present design an integral transducer determines the interelectrode gap of the converter. Initial designs for spacing actuators and their required cesium vapor seals are discussed. A novel hot-shell converter design incorporating active spacing control and low-temperature seals is presented. A converter incorporating the above features would be capable of near ideal-converter performance at high power densities. In addition, active spacing control can potentially completely eliminate short-circuit failures in thermionic converter systems.

• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: FG03-94ER81864
• OSTI ID: 442761
• Report Number(s): CONF-960805--
• Country of Publication: United States
• Language: English

Related Subjects

30 DIRECT ENERGY CONVERSION
CONTROL
DESIGN
ELECTRODES
HEAT PIPES
NESDPS Office of Nuclear Energy Space and Defense Power Systems
POSITIONING
THEORETICAL DATA
THERMAL DEGRADATION
THERMIONIC CONVERTERS
THERMIONIC EMITTERS