| 摘要 |
PROBLEM TO BE SOLVED: To extend the lifetime of an X-ray tube by reducing damage by the collision of positively electrified metal ions to the cathode of the electron gun of a microfocus X-ray tube. SOLUTION: A center axis 30 in the electron gun 18 of a negative electrode 12 in the X-ray tube does not go toward a rotary center axis 32 of a rotary positive electrode 14 but passes a position separated from the rotary center axis 32 by distance L. Thus, a positive electrode base line 38 for connecting a focus 36 formed on an inclined surface 20a of a target 20 to the rotary center axis 32 crosses the center axis 30 of the electron gun 18 with an open angle ofθ<SB>2</SB>at the focus 36. As a result, an equipotential line near the focus 36 of the target 20 does not cross the center axis 30 of the electron gun 18, so that the running direction of positively electrified metal ions generated on the target 20 changes, thus reducing the collision of the positively electrified metal ions to the cathode of the electron gun 18 greatly. COPYRIGHT: (C)2008,JPO&INPIT
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