X-ray tube

An X-ray tube, comprising:

• an anode including a target surface radiating X-rays in a main radiation direction from a first focal spot formed by collision of an electron beam;
• and
• a cathode arranged at a position opposite to the target surface of the anode, and including a first filament emitting the electron beam and a focusing electrode focusing the electron beam emitted from the first filament, the focusing electrode including a valley bottom part farthest from the first focal spot, a first inclined plane obliquely rising from the valley bottom part in a direction to the anode, a first focusing groove opened to the first inclined plane, and a first housing groove opened to the bottom surface of the first focusing groove to accommodate the first filament,
• wherein
• an axis passing through a center of the first focal spot and parallel to an X-ray tube axis is a reference axis, a plane including the reference axis and the main radiation direction is a first reference plane, and an angle formed inside by a first extending line and a second extending line intersecting on a side opposite to a side of radiating the X-rays with respect to the reference axis is referred to as a first angle θ1, where the first extending line is a virtual straight line extending from a boundary straight line between the valley bottom part and the first inclined plane along the first reference plane, and the second extending line is a virtual straight line extending from the target surface along the first reference plane and the target surface,
• θ1>0°
• the first housing groove has a long axis,
• the first focusing groove has a lone axis, and
• the long axis of the first housing groove is inclined from the long axis of the first focusing groove.