IMPREGNATED CATHODE AND MANUFACTURE THEREFOR AND ELECTRON GUN AND ELECTRONIC TUBE

摘要

PROBLEM TO BE SOLVED: To provide a stable electron emitting characteristic by restraining emission of an unnecessary electron and a particle produced from an excessive electron emitting substance. SOLUTION: An impregnated cathode 1A is positioned just under an electron emitting hole of a first grid, and is composed of a porous sintered body 10 having the surface being an electron emitting area 10a and a porous sintered body 11 having the surface being a peripheral area except for the electron emitting area. Porosity of the porous sintered body 10 is set larger than that of the porous sintered body 11. An electron emitting substance 1a is impregnated not only into the porous sintered body 10 having the electron emitting area 10a but also into the porous sintered body 11 corresponding to the peripheral area of the electron emitting area 10a, and a quantity of the electron emitting substance 1a per unit volume impregnated into the porous sintered body 10 is increased more than that impregnated into the porous sintered body 11.