| Popis: |
The principal problem which arises at construction of multibeam cathodes units is provision of small spread in emission parameters of separate emitters in the unit preserving the mechanical strength and the shape stability of the cathode unit. The problem is reduced to the task of effective attachment of emitters to their seats in the cartridge-holder of the unit. There exist some structures of multibeam cathode units in which the emitters are fixed in the cartridge-holder by means of rolling or welding. A disadvantage of such units is their insufficient mechanical strength and a large scatter of temperature between separate emitters particularly under thermomechanical loads. As a rule, the emitters are made of tungsten sponge impregnated with barium-calcium aluminate. A cure for these difficulties is soldering. In this connection, the emitters are inserted into the holes in the cartridge-holder and in this case, there is a clearance of a definite width are made between the emitter and the walls of the hole, while the solder is located both inside the clearance and on the side of the emitter, opposite to the emitting surface, the emitter being immersed in the hole of the cartridge-holder down to some definite depth. |
