| 摘要 |
PURPOSE:To obtain excellent resolution by making a cathode structure be composed of a flat plate filament for a small focal point and a coiled filament for a large focal point, both of which are installed in a focusing electrode of the cathode structure. CONSTITUTION:When a positive potential to a flat plate filament 23 for a small focal point is applied to a focusing electrode 13 by a power source, a coiled filament 24 for a large focal point and the electrode 13 are operated essentially in equipotential states. Hence, an electron beam focal point formed at a X-ray focal point position X on a rotary anode target 11 has a single- humped distribution e1 of electron density generated by the filament 23 on a flat electronic radiation surface. A focal point distribution of electron density generated by the filament 24 is double-humped e2. The small focal point is a X-ray focal point less than 0.2 mm in diameter and its size can be more largely changed by the bias potential applied to the electrode 13.
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