Patent ID: 6927538

Claim:
A photomultiplier tube comprising: a tube-shaped vacuum vessel extending along a tube axis, the tube-shaped vacuum vessel having a first end and a second end in relation to the tube axis; a photocathode positioned on the first end of the tube-shaped vacuum vessel, for converting incident light to electrons and emitting the electrons; a pair of electrically insulating base plates, each of the pair of electrically insulating base plates having a predetermined thickness; a plurality of dynodes arranged in n stages, the plurality of dynodes including through n th stage dynodes wherein n is an integer, the plurality of dynodes being supported between the pair of electrically insulating base plates and having secondary electron emitting surfaces formed on inner walls for multiplying electrons sequentially; and an anode for receiving the electrons multiplied by the plurality of dynodes; wherein at least one dynode from among the plurality of dynodes includes: the secondary electron emitting surface having a curved surface of an arcuate cross-section and a flat surface formed continuously and flush with the curved surface: first support portions extending outward from both ends of the curved surface on a base plate side; and second support portions extending outward from both ends of the flat surface on the base plate side and forming a prescribed angle with the first support portions; and wherein the pair of electrically insulating base plates is formed with first through-holes for receiving the first support portions and second through-holes for receiving the second support portions.