PURPOSE: To maintain the electron emission characteristic of an electron gun before mounting by blowing nonoxidizing gas into an impregnated type cathode during sealing processes.
CONSTITUTION: The surface of an Sc impregnated type cathode pellet 1 is covered by a thin film 2 made of Mo and a thin film 3 made of Sc2O3 is provided on the surface of the film 2. The pellet 1 is formed by a porous W base 4 having a hole therethrough and a vacant portion 5. The pellet 1 is pressed into a Ta cup 6 and then the Ta cup 6 and a Ta sleeve 7 are welded together while nonoxidizing gas such as Ar or N2 is blowed. During heating of the cathode a heater 9 comprising a W filament 8 corvered with alumina is used. In the preheating process of electron gun stem glass, that of electron tube neck glass and the annealing process of a sealed portion, sealing is performed while N, gas is sprayed to the cathode through a chip pipe 16. Thereafter the electron gun is heat-treated in order to evacuate the inside of the electron tube 10 and to activate the cathode 13.
TAKEUCHI KATSUSUE
KANNA KENICHI
