Abstract: A flat thermionic cathode is provided with a substrate having at least one main heating element thereon to produce at least one substantially localized area of heat and a sub-heating element to substantially define a heating area, the localized area being produced within the heating area. A cathode element including electron emissive material is disposed at the localized area. While the localized area tends to produce a temperature gradient directed from the localized area toward the perimeter of the substrate so as to create thermal stress in the substrate along the perimeter thereof, the sub-heating element reduces this temperature gradient and, consequently, the thermal stress.

Abstract: A thermionic cathode structure includes a ceramic base plate, a heater layer of tungsten coated on the ceramic base plate, a cathode lead layer of tungsten formed on a ceramic insulating layer covering the heater layer, a base metal layer coated on the cathode lead layer, and a cathode material coated on the base metal layer.

Abstract: In a cathode ray tube in which an electron gun directs one or more electron beams against a phosphor screen through an electron focusing lens, preferably of the unipotential type, constituted by a plurality of tubular electrodes arranged coaxially in succession along the tube axis with a relatively low potential being applied to one of the electrodes and a relatively high potential being applied to the other electrodes, and in which each electron beam is deflected, after passing through the focusing lens, so as to scan the screen in line-scanning and vertical directions; distortion of the landing spot of each beam on the screen, particularly when deflected toward the peripheral portions of the screen, is removed or compensated by forming the tubular electrode which is maintained at the relatively low potential of two axially divided tubular electrode portions having respective end plates or walls extending across their adjacent ends and formed with aligned apertures for the passage through the latter of each