Electron gun and method of assembly

Claim 1

An electron gun of the type comprising a series of electrodes in alignment along a gun axis, at least one of said electrodes comprising: a. a support member comprising a cup having a central opening in alignment along said gun axis in the bottom thereof; b. an apertured member inserTed in said support member and having an aperture in alignment with said gun axis, said apertured member comprising: i. an outer aperture cup with a centrally apertured cup-shaped depression in the bottom, said depression being inserted fully into said support cup opening, the outside dimensions of said depression being sufficiently matched mechanically to the inside dimensions of said support member opening to prevent axial and radial play between said outer cup and support member; ii. an inner aperture cup with an aperture in the bottom thereof fixed inside said outer cup, the outside dimensions of said inner cup being sufficiently less than the inside demensions of said outer cup to permit radial movement between said outer and said inner cups, said inner cup aperture being aligned with said outer cup aperture; and iii. the configuration of an inside portion of said support member being mechanically matched to the configuration of an outside portion of said apertured member, whereby the relative orientations of said members are mechanically determined on insertion of said apertured member by intimate physical contact with said inside and outside portions, wherein said inside portion of said cup is the inside bottom surface and portions of the inside surface of said central opening in the bottom.