To provide a photomultiplier tube achieving great improvement of response time characteristics with a structure capable of producing a large volume.
The photomultiplier tube is provided with a closed vessel (100). In the closed vessel (100), a photocathode 200, a dynode unit (400) containing at least a dynode group of one system, and a focus electrode unit (300) arranged between the photocathode (200) and the dynode unit (400) are stored. The focus electrode unit (300) is set at the same electric potential as a second dynode (DY2) arranged at a position at which secondary electron from a first dynode (DY1) emitting the secondary electron in correspondence with incidence of a photoelectron reaches, and a separating plate (332) for dividing the second dynode (DY2) into two parts in its longitudinal direction is provided.
YAMAGUCHI AKIHIKO
Shiro Terasaki
Satoru Ishida