A COMPARATIVE STUDY OF CYLINDRICAL, ELLIPTICAL AND PRISMATIC FORMS OF ELECTRONIC TUBES

Abstract

In a previous study of the design shapes of an electronic diode, the prismatic form was shown to be superior to the cylindrical form, from the standpoint of the design parameter Kd defined as the ratio of the volume of the vessel to the surface area of the cathode. In the present paper the study is extended to include the condition of space-charge saturation in the device. To facilitate analysis a third form of tube is considered, in addition to the cylindrical and prismatic forms. This consists of a flat strip cathode surrounded by an anode of thin elliptical cross section. By the technique of conformal transformation,equivalence is set up between a diode having the elliptical shape and a cylindrical diode. The equivalent structures possessing the same electrostatic capacitance per unit length and giving approximately the same space charge saturated current are then compared as to their design parameters. The thin elliptical diode is found to have a decisively better design parameter than the equivalent cylindrical diode. A further comparison of equivalent elliptical and prismatic diodes shows the latter to be slightly superior to the former. The eIliptical form helps to set up equivalence between the prismatic and cylindrical forms of diodes. From the point of view of physical construction,it is likely to provide a more stable structure than the prismatic shape.