| 摘要 |
<p>An X-ray tube apparatus comprises an X-ray tube which includes a vacuum envelope and an anode target (8) and a cathode assembly (6) which are disposed within the vacuum envelope opposing each other. The cathode assembly has a flat-plate like filament (20) for generating an electron beam, and a beam shaping electrode (40) insulated from this filament (20). The beam shaping electrode (40) is formed with a beam limiting aperture (42) for passing therethrough a part of the electron beam emitted from the filament (20), and a focussing dimple (44) so as to focus the electron beam. When d2 and a3 are assumed to represent the depth of the focussing dimple (44) and the distance between the target surface and the top surface of the focussing dimple (44) opposing this target surface, respectively, the value of the ratio of d3 to d2 satisfies the inequality 1.0≤ d3/d2 ≤ 4.0.</p> |
