| 摘要 |
PURPOSE:To improve detection accuracy of an incident position, by unifying the thickness of a rectangular light entry window along its longitudinal direction, and bending it in the vertical direction at a fixed curvature so as to form plural emission surfaces separated from each other facing to photoelectric surfaces on plural dynode members. CONSTITUTION:A light entry window 7 is bent at a fixed curvature in a direction vertical to its longitudinal direction and its curvature center is located in the position shifted to the side of the first dynode member from the central axial line D-D of a photomultiplier 1. Accordingly, photoelectrons can be made to be surely incident on the emission surface 35 of the first dynode member 20. Further, since a zonal part 39 having a small secondary electron emission ratio is formed between the emission surfaces 35 and 36, the photoelectrons incident on this zonal part 39 do not emit secondary electrons. Thereby, neighboring emission surfaces are separated from each other and the secondary electrons emitted from the first dynode member 20 are surely directed to the emission surface facing to the second dynode member 21 for enabling mixture to be efficiently checked.
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