GB478812A - Improvements in and relating to electron discharge tubes - Google Patents

Abstract

478,812. Discharge apparatus. HARRIES, J. H. O. May 25, 1936, No. 14796. [Class 39 (i)] In an electron-discharge tube of the kind comprising a cathode, an accelerating electrode and an anode and in which the distance between the accelerating electrode and the anode is so chosen that the rate of change of the distance curve is positive or not more than slightly negative, as described and claimed in Specifications 380,429 and 385,968, rod-like directing electrodes are provided which are so positioned in relation to the electron discharge as to direct the electrons in a comparatively confined path towards the anode, whereby the density of the electron stream is increased. The effect of the space charge in producing a potential minimum in the space between the accelerating electrode and the anode is thereby increased, and smaller anode diameters may be used. In the form shown, a flattened equipotential cathode 14 is surrounded by lenticular control and accelerating grids 11, 10 and a circular anode 1. In the space between the accelerating grid and anode, and outside the region between the control grid and its projection on the anode perpendicular to its greatest diameter, are placed four rod directing electrodes 17 of circular cross-section similar in dimensions to the electrode support rods 7. The rods may be of non-circular cross-section with their greatest transverse dimension parallel to the electron stream and may alternatively be placed between the control and accelerating grids or between the control grid and the cathode. They are maintained at about cathode potential and may be connected to the cathode inside the valve. Dimensions are given for the example described.