A cylindrical X-ray tube having an outer insulating layer, a cathode electrode and an anode electrode disposed at both ends of the outer insulating layer, a gate electrode disposed between the cathode and anode electrodes, an emitter, and a target, comprises an inner insulating layer which is disposed between the cathode electrode and the outer insulating layer, is formed to extend downward in a coaxial direction with the outer insulating layer, and is pre-adjusted in order to secure an insulating distance between the cathode electrode and the gate electrode. Thus, by providing a separate internal insulating layer extending coaxially with the external insulating layer between the cathode electrode and the external insulating layer, the insulating distance between the cathode electrode and the gate electrode, the insulating distance between the cathode electrode and the anode electrode may be easily adjusted, so that a desired insulating capability can be secured.

An x-ray tube includes an electron emitter and a cathode cup having a recess that holds the electron emitter. The recess has a bottom surface, and a shield is positioned in the recess between the electron emitter and the bottom surface. The shield is configured to receive deposited sublimated emitter material and to maintain the sublimated emitter material away from the electron emitter.

An emitter for a closed x-ray tube includes an emitter body formed of a low work function emitter material, the emitter body having a major surface and a secondary surface. The major surface is adapted for emission of electrons from the low work function material. The emitter assembly is adapted to reduce an emission current density emitted from the secondary surface of the emitter body, as compared to the major surface.

An x-ray tube includes an electron emitter and a cathode cup having a recess that holds the electron emitter. The recess has a bottom surface, and a shield is positioned in the recess between the electron emitter and the bottom surface. The shield is configured to receive deposited sublimated emitter material and to maintain the sublimated emitter material away from the electron emitter.

A computer tomograph (1) for mammographic x-ray imaging includes a MBFEX tube (20) and a flat-bed x-ray detector (30). Cathodes (40) are arranged in a fixed manner in rows in the MBFEX tube (20), the cathodes (40) being provided for the field emission of electrons. Geometry, radiation density and wavelength range of an x-ray beam (b) can be set. The MBFEX tube (20) is movable parallel (z) to the flat-bed x-ray detector (30). The flat bed x-ray detector (30) includes a moveable x-ray screen (31), the opening of which can be set. Using the x-ray screen (31), an imaging area (A) on the detector surface (D) of the flat-bed x-ray detector (30) can be selected and moved. Compared to conventional computer tomographs having rotating x-ray components, the computer tomograph (1) has a lighter and more compact design, with which a particularly small focal spot size is achieved.

The present disclosure relates to a method and system for adjusting a focal point position of an X-ray tube. The method may include: obtaining a first thermal capacity and a first position of a focal point of an X-ray tube; obtaining a second thermal capacity of the X-ray tube; determining a second position of the focal point the X-ray tube based on the second thermal capacity; determining a target grid voltage difference of a focusing cup of the X-ray tube based on the first position and the second position of the focal point; and adjusting the X-ray tube based on the target grid voltage difference.

According to one embodiment, an X-ray tube, including a cathode including a filament including a leg portion extending from a coil to a distal portion and including a corner portion at the distal portion, a support terminal including a gap, and including an opening portion in which the gap is opened and a bottom portion located on a side opposite to the opening portion, and a cathode cup being connected to the support terminal, the distal portion being located in the gap, the support terminal including a protruding portion protruding in the gap, being located more closely to the bottom portion side than the distal portion, and being joined to the corner portion of the leg portion.

An emitter for a closed x-ray tube includes an emitter body formed of a low work function emitter material, the emitter body having a major surface and a secondary surface. The major surface is adapted for emission of electrons from the low work function material. The emitter assembly is adapted to reduce an emission current density emitted from the secondary surface of the emitter body, as compared to the major surface.

An electron gun, an X-ray source and a CT device are provided. The electron gun includes a body having a first end portion and a second end portion opposite to each other, wherein the first end portion is a connecting end portion; an internal cavity is formed in the body and has an opening positioned on the second end portion; a cathode, a grid, a compensation electrode and a focus electrode, orderly arranged in the internal cavity in a direction from the first end portion to the second end portion.

An electron gun includes a cathode including an electron emitting portion, an extraction electrode for extracting electrons emitted from the electron emitting portion, and a focusing electrode for focusing the electrons extracted by the extraction electrode. The focusing electrode includes an outside electrode having a tubular shape, and an inside electrode arranged inside the outside electrode. The inside electrode defines a first space having a columnar shape, and includes a first surface on a side of the cathode, and a second surface on an opposite side of the first surface. An inside surface of the outside electrode and the second surface of the inside electrode define a second space. The inside electrode includes an electron passage hole, and a communicating portion which makes the first space and the second space communicate with each other.