An analysis is presented of the effect of an electric field upon a "patchy" thermionic emitter. The model assumed for the analysis is that of parallel strips in a plane arranged with adjacent strips alternating between two particular values of work function. Calculations are made showing the dependence of emission on various parameters in the model. Some comparisons are made between the above analysis, the Nottingham strip theory for field effects, and experimental data presented by Nottingham. On the basis of the above analysis a simple model is presented for estimating the field effect on thermionic emission. Results from the simplified model are compared with those from the more detailed analysis.
ACKNOWLEDGMENT 16Calculation of AO(eT) 19Summary 2:5References 27 IV Space Charge Analysis for Low Pressure ThermionicDiodes (Warner) P-8 introduction 28The in that report the ideal converter performance was der-ined and the details of the fundamental efissiaon processes were analyzed and related to the recuirements for ideal converter operation. This thereby provided an extensive analysi8 of emission-limited converter operation.The continuation of the proerran, the results of which are included in the present report, extends some of the theories of the emission processes, but emphasizes the processes occurring in the interelectrode space and the relation and importance of the emission characteristics on the transport effects. The work of this year, therefore, represents a logical extension of the earlier work in that the knowledge of the emission processes is coup~led with studies of the transport processes in order to effect a more complete understanding of thermionic energy conversion. The results are summarized in the following section. The remainder of the report consists of detailed articles on problems investigated during the past year.Predominzajtly, the conventions used in this report are those proposed for the 1962 Colorado Springs Symposium on Thermionic Power Conversion.When the discussion is directly related to gaseous discharges or vacuum electronics, however, and when extensive reference is made to published A!"7979 1 Ii. SUMMARY OF RESULTSSome of the work of the past year has been a continuation of the study 6f emission phenomena and the emisSion6limited thermionic converter. The resutrS of this study are discussed in Section III.Results of the studies of the transport processes and the interaction of emission and transport effects ar discussed in Sections IV, V, VI and VII. The inclusion of the effects of adatoms has shown that a major effect in expla~ning the maximum in the work function change may be due to the polarizability of the adatoms. Furthermore, at large coverages where this theory is inadequate, the lateral bonding of the cesium and possible accom- AI-79793 panying effects such as changes in polarizability may also be extremely important. SPACE CHARGE ANALYSIS FOR LOW PRSSUE THE11IONIC DI0DESA space charge analysis of a collisionless, plane electrode thermionic converter has been performed. With, both ions and electrons emitted, the potential distributions can assume a variety of forms. This report Completely systematizes these SlUtioinsiThe space charge problem is first considered for infinite spacing, and the potential distributions are Characterized by the collector potential and the potential at which the electric field first vanishes. For a given emitted ion-to-electron ratio, the diode ion and electron currents are easily extracted as a function of collector potential, and thus the volt-ampere curve can be plotted. The resulting volt-ampere characteristics extend continuously from minus infinity to plus infinity, so that the load line always yields an operating point. he ptes...
Capture cross sections of electron irradiation induced defects in 6H-SiC
The plasma physics of thermionic converters is discussed in an attempt to develop a coherent physical picture of this aspect of the converter in all regions of operation. Emphasis is placed on the presentation of simple physical models consistent with experimental data: The usefulness of certain characteristic features of the I–V curve, in determining the physical processes governing converter operation, is pointed out. Nine regions of converter operation are identified by these features of the I–V curve and are discussed. The importance of two parameters of converter operation, the pressure—spacing product pd, and the relative amount of emitter-surface ion generation β, in controlling converter behavior is emphasized. The particular values of pd and β control which of the nine regions of converter operation appear on a particular I–V curve.
Articles you may be interested inThe effect of ion drift on the sheath, presheath, and ion-current collection for cylinders in a collisionless plasma Phys. Plasmas 12, 062109 (2005); 10.1063/1.1924392 Novel compact electrostatic ion-current detector using a self-collection method for secondaryelectron suppression Rev.Effects of hydrogen ion implantation on Al/Si Schottky diodes Appl. Phys. Lett. 50, 1530 (1987); 10.1063/1.97821 Effect of antimony ion implantation on Alsilicon Schottky diode characteristicsAn experimental and theoretical study is made of current nonsaturation phenomena in cesium vapor, thermionic diodes. It is shown that ion flow from the plasma to the emitter electrode produces a significant nonsaturation effect. It is also shown that this ion current produces a high-sheath field at the emitter which accentuates the nonsaturation through the Schottky and anomalous Schottky effects. These effects are incorporated into an analysis of diode behavior. It is shown that the expected diode behavior due to ioncurrent and Schottky effects is consistent with available experimental data.implications of plasma-transport processes due to electron-neutral collisions are becoming clear.4-6 The significance of electron-ion contributions to cesium plasma transport phenomena has been studied. 7 -9 Descriptions of the complicated, multistage ion-generation and recombination processes have been de-4 N. S.
A comprehensive experimental and theoretical analysis is presented for the electron-rich, unignited mode of a cesium-vapor thermionic diode. The theoretical inverse spacing dependence of the apparent saturation current is found to be in agreement with experiment. The theoretical and experimental coefficient of this dependence are found to be in agreement if one assigns a value Pc=700 cm−1 Torr−1 to the electron-neutral collision probability. This value is consistent with other available information. Potential distributions are calculated. Full theoretical and experimental volt-ampere curves are compared. Some of the assumptions in the theoretical analysis are examined in detail.
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