Gridded convergent flow electron gun for linear beam tubes

In an electron gun;

• an evacuable envelope structure;
• thermionic cathode emitter means having a concave emitting surface generally approximating a figure of revolution for emitting a stream of electrons;
• an accelerating anode means spaced from said cathode emitter and having a central aperture of substantially smaller diameter than the diameter of the concave emitting surface of said cathode emitter, such anode central aperture being disposed in axial alignment with the axis of revolution of said concave emitting surface of said cathode emitter for accelerating and converging a stream of electrons through said aperture into a linear beam of electrons;
• a multi-apertured concave control grid means disposed overlaying said concave emitting surface of said cathode emitter in spaced relation therefrom for controlling the beam current drawn from said cathode through the apertures in said control grid means;
• control grid support means for supporting said control grid from the periphery thereof and disposed in electrically insulative and substantially thermally insulative relation relative to said cathode emitter means;
• said control grid support means being connected in heat exchanging relation with said control grid and including, a thermally conductive support structure surrounding said cathode emitter in thermally insulative relation thereto and thermally communicating through the evacuable envelope of the gun to the surrounds for conducting heat from said control grid to the surrounds of the electron gun and having an electrically insulative thermally conductive first portion interposed within said evacuable envelope in heat exchanging relation between the periphery of said control grid means and an electrically conductive second portion of said grid support structure, said second portion being in physical contact with a portion of said evacuable envelope, said control grid means is serrated to define a plurality of radially directed fingers at the periphery of said control grid, and wherein said fingers are joined to said electrically insulative and thermally conductive first portion of said grid support structure, the peripheral extent of each of said fingers is greater than the space between adjacent fingers.

In an electron gun;

• an evacuable envelope structure;
• thermionic cathode emitter means having a concave emitting surface generally approximating a figure of revolution for emitting a stream of electrons;
• an accelerating anode means spaced from said cathode emitter and having a central aperture of substantially smaller diameter than the diameter of the concave emitting surface of said cathode emitter, such anode cnetral aperture being disposed in axial alignment with the axis of revolution of said concave emitting surface of said cathode emitter for accelerating and converging a stream of electrons through said aperture into a linear beam of electrons;
• a multi-apertured concave control grid means disposed overlaying said concave emitter surface of said cathode emitter in spaced relation therefrom for controlling the beam current drawn from said cathode through the apertures in said control grid means;
• control grid support means for supporting said control grid from the periphery thereof and disposed in electrically insulative and substantially thermally insulative relation relative to said cathode emitter means;
• said control grid support means being connected in heat exchanging relation with said control grid and including, a thermally conductive support structure surrounding said cathode emitter in thermally insulative relation thereto and thermally communicating through the evacuable envelope of the gun to the surrounds for conducting heat from said control grid to the surrounds of the electron gun and having an electrically insulative thermally conductive first portion interposed within said evacuable envelope in heat exchanging relation between the periphery of said control grid means an an electrically conductive second portion of said grid support structure, said second portion being in physical contact with a portion of said evacuable envelope, said second portion of said grid support structure includes a tubular metallic member surrounding said cathode emitter, and said first portion includes an annular ceramic member joined at one end to said tubular metallic second portion and at the other end to the periphery of said control grid means, said tubular metallic member is made of a copper impregnated tungsten matrix comprising by weight a preponderance of tungsten.