Abstract: An electron gun for high brightness including a LaB.sub.6 single crystal cathode having a (100) plane on at least part of a main electron beam emission surface of a cathode tip having a top and a Wehnelt having a tapered surface defining an interior angle similar to or greater than a vertical angle of said cathode tip.

Abstract: A thermionic emission cathode of a single crystal made of the calcium hexaboride type crystaline structure comprises a top surrounded by natural face inherent to the axial direction of the single crystal.

Abstract: A thermionic cathode supporting device which comprises an electroconductive member adapted to support a thermionic cathode tip and a tip supporting heaters which hold said tip, a pressing means for resiliently pressing the above mentioned members from the outside thereof. The device is so arranged that the pressing force is easily adjustable and can be miniaturized, and applicable for the various different types of cathode devices of an electron gun or the like.

Abstract: A method for manufacturing a thermionic cathode is provided which comprises cutting a bar from a multi-layer structure having a first layer of thermoelectron emissive compound and a third layer of metal of high melting point, a second layer of reaction barrier being interposed between said first and third layers, the bar being cut in a direction substantially perpendicular to that of the layers, sharpening the end of the first layer of the bar and then providing current terminals with the third layer of the bar. According to the method of the invention, a thermionic cathode capable of emitting stable electron beams of high intensity for a long period of time can be manufactured.

Abstract: A thermionic cathode for an electron beam device is provided which comprises a first layer of thermoelectron emissive compound sharpened towards a point, a third layer of metal of high melting point and a second layer of reaction barrier interposed between the first and third layers, current terminals being attached to said third layer. According to the invention, a thermionic cathode capable of emitting stable electron beams of high intensity for a long period of time can be manufactured.