| 摘要 |
PROBLEM TO BE SOLVED: To provide an X-ray tube having small distortions for the focal point of a plurality of electron beams with different sizes formed on the anode. SOLUTION: On a focusing electrode 21 disposed to face the target surface of the anode where X-ray is generated, a valley bottom wall face M0 located farthest from the anode and two slanting wall faces M1, M2 sandwiching this valley bottom wall face M0 are formed, and nearly rectangular focusing grooves 22a through 22c are formed on these three wall faces M0, M1, M2, respectively. And filaments 23a to 23c are disposed in the nearly rectangular focusing grooves 22a to 22c, where the largest focusing groove 22a and filament 23a are disposed on the central valley bottom wall face M0.
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