Abstract: An electron gun with one directly heatable initial cathode (2), one indirectly heatable second blocking cathode (3) and one focusing electrode (17). The focusing electrode (17) presents an initial centering region (18) and, by means of supporting braces, the blocking cathode (3) is fixed concentrically in a carrier ring (19) presenting a second centering region complementary to the first centering region (18). This permits the blocking cathode (3) to be introduced into the focusing electrode from the back by means of the carrier ring (19), and the carrier ring (19) is secured by means of a locking ring (24).

Abstract: In a mounting device for electrically heated, spirally wound wire cathodes in electron guns, two mounting posts joined together by an insulator are configured as sector-shaped sections of a hollow cylinder, and have each a circumferential groove on its end remote from the insulator. The surfaces defining the grooves are parts of common circular and cylindrical surfaces, and the mounting ends of the cathodes are of a configuration approximately complementary to that of the grooves in the mounting posts. The mounting ends therefore lie in a spring-biased and form-fitting manner in the circumferential grooves.