Patent ID: 8031839

Claim:
An X-ray tube comprising: a vacuum enclosure; a cathode electron gun formed in the vacuum enclosure and comprising a filament coil which is centered around an X-ray tube central axis and has a longitudinal direction perpendicular to the X-ray tube central axis; an anode formed in the vacuum enclosure to face the filament coil on the X-ray tube central axis; and an X-ray radiation window formed, to face the anode, in a wall of the vacuum enclosure in a direction perpendicular to the longitudinal direction of the filament coil, wherein: a distance from the X-ray tube central axis to an outer side surface of the cathode electron gun in the direction perpendicular to the longitudinal direction of the filament coil is less than that from the X-ray tube central axis to an outer side surface of the cathode electron gun in the longitudinal direction of the filament coil, a distance from the X-ray tube central axis to the wall of the vacuum enclosure, in which the X-ray radiation window is formed, in the direction perpendicular to the longitudinal direction of the filament coil is less than that from the X-ray tube central axis to a wall of the vacuum enclosure in the longitudinal direction of the filament coil, an outer side surface of the cathode electron gun in the direction perpendicular to the longitudinal direction of the filament coil is formed into a flat surface parallel to the longitudinal direction of the filament coil, and a wall of the vacuum enclosure in the direction perpendicular to the longitudinal direction of the filament coil is formed to have a flat surface parallel to the longitudinal direction of the filament coil.