Robust electrode with septum rod for biased X-ray tube cathode

An electrode for gridding and/or focusing at least one electron beam from an emitter, the electrode comprising:

• a ring-shaped housing defining a central aperture therein;
• a width electrode comprising a pair of electrode sections disposed on the housing on opposed sides of the central aperture between and above the emitter to affect the electron beam in a width direction;
• a length electrode comprising a pair of electrode sections spaced from the width electrode and above and over the emitter to affect the electron beam in a length direction;
• a rod extending across the central aperture between the electrode sections, wherein the rod is joined to the housing at only one end.

A method for affecting the intensity and shape of a focal spot of an electron beam emitted from an X-ray tube, the method comprising the steps of:

• providing an X-ray tube including a cathode assembly comprising a pair of emitters for generating a pair of electron beams, a first electrode for gridding and/or focusing the pair of electron beams, the first electrode defining a central aperture with a pair of electrode sections disposed on opposed sides of the central aperture and a rod extending across the central aperture between the electrode sections, a second electrode comprising a pair of electrode sections between and/or perpendicular to the pair of electrode sections of the first electrode, and a target for generating X-rays when impinged upon by the electron beams;
• passing a current through at least one of the pair of emitters to generate an electron beam;
• biasing the first electrode with a voltage to grid or focus the electron beam as the electron beam passes through the central aperture to one or both sides of the rod;
• biasing the rod with a voltage of between within +/−2 kV from the biasing voltage applied to the first electrode;
• and
• biasing the second electrode to focus the electron beam.