Electron gun having a low capacitance cathode and grid assembly

Claim 1

An electrode assembly for an electron discharge device, comprising: an annular dielectric support member having a front face, a rear face, and a central passage formed by a frusto-conical major interior surface extending between a circular front opening adjacent said front face and a substantially smaller circular rear opening adjacent said rear face, a first, disk-shaped grid electrode, of a size not substantially exceeding that of said smaller opening, disposed overlying the smaller opening and bonded at its periphery to the support member's rear face, a second nonplanar grid electrode bonded to the support member's front face, said second electrode including a recessed portion extending into said front opening to position a central region of the second electrode in closely-spaced relation to said first grid electrode, said recessed portion having a frusto-conical surface disposed in axially-aligned, closely-spaced relation to said frust-conical interior surface of the support member, a cathode electrode having an activated, electron-emissive surface, and means, including a dielectric member bonded to the rear surface of said annular support member, mounting said cathode electrode with its electron-emissive surface closely adjacent said first grid electrode, said first and second grid electrodes each including a central aperture, the apertures of said electrodes and the electron-emissive surface of said cathode being arranged in mutual alignment.