| 摘要 |
<p>An inner surface of an electron-multiplier hole (14) includes a first curved surface (19a) and a second curved surface (19b) that face each other. The first curved surface (19a) extends from an edge of an input opening (14a) in such a way as to face the input opening (14a), and is shaped like a substantially circular arc having a predetermined radius. The second curved surface (19b) extends from an edge of an output opening (14b) in such a way as to face the output opening (14b), and is shaped like a substantially circular arc having a predetermined radius.</p> |
