Thermionic Space Charge Oscillations

• Main Author: Carl, William
• Format: Others
• Published: TopSCHOLAR® 1971
• Subjects: Physics
• Online Access: http://digitalcommons.wku.edu/theses/1038; http://digitalcommons.wku.edu/cgi/viewcontent.cgi?article=2041&context=theses

Thermionic electrons emitted into a potential well will produce radiation, the frequency of which is determined by the transit time of the electrons. This paper investigates the case where radiation is produced by a vacuum tube in which two Pierce guns face each other, one acting as the emitter, the other acting as a reflector. Symmetry and the focusing of the electron beam by the Pierce guns make it possible to make an accurate determination of the electron transit time. Measurements showed that the period of the oscillation was 1.5 times the period required for an electron to traverse the well and return to the emitting cathode. Attempts to account for this period by presently accepted modes of oscillation were unsuccessful. A model developed to explain the observations resulted from establishing compatibility of the electron flow in the emitter and the cathode-accelerator space. A conclusion drawn from the model is that conventional calculations of the emitted current density should be modified to account for the shift in energy levels of the electrons in the emitter as a result of the surface-directed electron drift.