RESEARCH ON IMPROVED THERMIONIC CONVERTER FOR SPACE OPERATIONS. Final Report, January 1, 1960-December 31, 1961
: 9 = : ; 8 ; 7 : : 7 : ? 6 >Cs plasma diode shows that operating conditions can be achieved for which there exists no simultaneous solution of the space charge and converter equations which relate current, voltage, and load impedance. These conditions correspond to those for which internal relaxation oscillations were experimentally observed in a Cs vapor type thermionic energy converter. Examination of the normalized distance parameter used in the analysis indicates that potential distributions having a large number of potential maxima and minima may exist in the Cs plasma diode. This explains some irregularities found in the load characteristic and in plasma temperature measurements for the Cs diode. The conversion of heat into electromagnetic energy is achieved by utilizing the intrinsically unstable space- charge properties of a thermionic Cs plasma diode. Experimental studies of this phenomenon are described. A physical model for the observed relaxation oscillations is proposed which is in qualitative agreement with experiments. A novel method of representing the potential energy diagram for the plasma is described; this method facilitates the understanding of the interaction between plasmas and solids. Based on this model, a detailed plasma energy balance for different types of cathode materials is given. Experimental studies of plasma synthesis are described where ions and electrons originate at different sources. The experimental tube operating as an energy converter had a power output of about 0.55 w/cm/sup 2/ at a cathode temperature of 1100 deg C. Theoretical and experlmental studies of the duo-emitter diode are described. In this diode an electron emitter and an ion emitter are facing each other. This geometry simulates the plasma triode geometry and allows studies of plasma generation as well as cathode and ion emitter materials and their interaction. Microwave and d-c experiments corroborate the theory. Some physical properties of the Li ion emitter Beta-Eucryptite were investigated and the application of this material for the production of an electron-Li ion'' plasma are described. Beta- Eucryptite is a ceramic material which has the ability to emit Li ions when heated to 1000 to 1300 deg C. In contrast to other types of ion emitters using the process of resonance ionization of neutral atoms on a hot surface, the alkali metal is here supplied not from the vapor phase but is stored in the emitter itself. ln this sense BETA -eucryptite is a true ion emitter. This compound is one of the most copious ion emitters known. A theory is developed for ion emission from film coated metal surfaces. Based on this theory calculations are made of the ion emitter temperature (T*), which corresponds to the onset of saturated ion emission. T* is found to be dependent on the physical properties of the metal, the film, and on the film atom arrival rate. Theoretical and experimental values of T* are in excellent agreement. For Cs fllms at constant Cs atom arrival rate, T* is expected to vary about 200 deg C among the transition metals. For each metal, an increased Cs atom arrival rate corresponding to a change in the Cs bath temperature of 100 deg C cause T* to increase by about 300 deg C. Experimental studies of the plasma triode are described. Using the duo- emitter diode geometry tests of the performance of a large number of ion emitter materials were made in the presence of the L-cathode. It was found that Hf and graphite give excellent ion emission at temperatures equal to or lower than that of the L-cathode. The construction of a plasma triode having a common heat source for the two emitters is described. This structure uses a metallized ceramic base onto which the heater, the cathode and the ion emitter are brazed. This assures a uniform temperature distribution for the emitter. A discussion of the relative merits of three approaches to low temperature thermionic power conversion is made. These
- Research Organization:
- David Sarnoff Research Center, Princeton, N.Y.
- DOE Contract Number:
- AF19(604)-6175
- NSA Number:
- NSA-16-033928
- OSTI ID:
- 4743621
- Report Number(s):
- NP-12090
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-62
- Country of Publication:
- United States
- Language:
- English
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