X-ray tube with improved control electrode arrangement

Claim 2

An electron emissive device comprising: a cathode means including an electron emitter for generating electrons; an anode for receiving said electrons; an auxiliary electrode positioned entirely behind said emitter of said cathode means with respect to said anode; means for applying a potential between said cathode means and said anode to cause electrons to flow from said cathode means to said anode; and means for connecting said auxiliary electrode to a source of positive electrical potential with respect to said emitter thereby drawing electrons from said cathode means and decreasing the flow of electrons from said cathode means to said anode.

Claim 3

An electron emissive device as set forth in claim 1, said cathode means comprising a filament.

Claim 4

An electron emissive device as set forth in claim 1, said cathode means comprising a metal body having an electron focusing cup recess Therein, and a filament for thermionic generation of electrons mounted within said recess.

Claim 5

An electron emissive device as set forth in claim 3, said metal body having a front surface wherein said focussing cup recess is provided and a rear surface, said auxiliary electrode being positioned adjacent to but spaced from said rear surface, said body having an opening extending from said rear surface into said recess, whereby upon application of a positive potential to said auxiliary electrode electrons will flow from said filament to said auxiliary electrode through said opening.

Claim 6

An x-ray tube comprising: a cathode means including an electron emitter and a focusing electrode insulated from said emitter for generating electrons, an anode for receiving said electrons; an auxiliary electrode positioned behind said emitter with respect to said anode and insulated from said focusing electrode; means for applying a potential between said cathode and said anode to cause electrons to flow from said cathode means to said anode; and means for connecting said auxiliary electrode to a source of positive electrical potential with respect to said cathode means thereby drawing electrons from said cathode means and decreasing the flow of electrons from said cathode means to said anode.

Claim 7

An x-ray tube comprising: a cathode means including an electron emitter and a focusing electrode insulated from said emitter for generating electrons, an anode for receiving said electrons; an auxiliary electrode positioned behind said emitter with respect to said anode and insulated from said focusing electrode; means for applying a potential between said cathode and said anode to cause electrons to flow from said cathode means to said anode; and means for connecting said auxiliary electrode to a source of positive electrical potential with respect to said cathode means thereby drawing electrons from said cathode means and decreasing the flow of electrons from said cathode means to said anode.

Claim 8

An x-ray tube in which the improvement comprises: a cathode means including a pair of filaments for emitting electrons; anode means for receiving said electrons; a focusing cup structure for said filaments comprising a pair of metal bodies each having a focusing cup recess formed therein, said bodies being electrically insulated from each other; said filaments being mounted one in each of said recesses and electrically insulated from said bodies; at least one auxiliary electrode insulated from said focusing cup structure and positioned behind said filaments relative to said anode; means for connecting said filaments to a source of electrical potential; and means for connecting each of said bodies to a source of negative electrical potential relative to the filament potential independently of the other body whereby a cutoff bias can be applied selectively to said bodies to restrict flow of electrons from a selected one of said filaments to said anode.

Claim 9

An x-ray tube in which the improvement comprises: a cathode means including a pair of filaments for emitting electrons; anode means for receiving said electrons; a focusing cup structure for said filaments comprising a pair of metal bodies each having a focusing cup recess formed therein, said bodies being electrically insulated from each other; said filaments being mounted one in each of said recesses and electrically insulated from said bodies; at least one auxiliary electrode insulated from said focusing cup structure and positioned behind said filaments relative to said anode; means for connecting said filaments to a source of electrical potential; and means for connecting each of said bodies to a source of negative electrical potential relative to the filament potential independently of the other body whereby a cutoff bias can be applied selectively to said bodies to restrict flow of electrons from a selected one of said filaments to said anode.

Claim 10

An x-ray tube as set forth in claim 6 in which the auxiliary electrode is positioned rearwardly of at least one of said metal bodies, and means for connecting said auxiliary electrode to a source of positive potential with respect to the filament in the adjacent body whereby upon application of said positive potential electrons will be drawn from such filament to said auxiliary electrode.

Claim 11

In an x-ray tube: an anode; a focusing electrode comprising a conductive metal body having at least one focusing cup recess formed therein in the surface facing said anode and at least one opening extending from said recess to the opposite surface of said body; a cathode filament mounted in said recess for generating electrons for impingement upon said anode having a lead extending through said opening; an auxiliary electrode of an electrically conductive material positioned behind said filament relative to said anode and adjacent to said opposite surface but electrically insulated from said focusing electrode; means for connecting said filament to a source of electrical energy; means for connecting said focusing electrode and anode to a source of electron accelerating electrical potential; and means for connecting said auxiliary electrode to a source of electrical potential positive with respect to said filament whereby at least some of the electrons generated at said filament will be drawn to said electrode thereby lessening the flow of electrons from said cathode to said anode.

Claim 12

In an x-ray tube: an anode; a focusing electrode comprising a conductive metal body having at least one focusing cup recess formed therein in the surface facing said anode and at least one opening extending from said recess to the opposite surface of said body; a cathode filament mounted in said recess for generating electrons for impingement upon said anode having a lead extending through said opening; an auxiliary electrode of an electrically conductive material positioned behind said filament relative to said anode and adjacent to said opposite surface but electrically insulated from said focusing electrode; means for connecting said filament to a source of electrical energy; means for connecting said focusing electrode and anode to a source of electron accelerating electrical potential; and means for connecting said auxiliary electrode to a source of electrical potential positive with respect to said filament whereby at least some of the electrons generated at said filament will be drawn to said electrode thereby lessening the flow of electrons from said cathode to said anode.