Patent ID: 7397184

Claim:
A photomultiplier comprising: a sealed container of which the inside is kept in a vacuum state; a photocathode, placed in said sealed container, emitting photoelectrons to the inside of said sealed container in response to light having a predetermined wavelength; a dynode unit placed in said sealed container and including a plurality of stages of dynodes emitting secondary electrons in response to the photoelectrons reached from said photocathode to cascade-multiply sequentially the secondary electrons, said dynode unit having, at least, a first dynode emitting the secondary electrons in response to the photoelectrons reached from said photocathode, and a second dynode emitting the secondary electrons in response to the secondary electrons reached from said first dynode; an anode, placed in said sealed container, taking out the secondary electrons cascade-multiplied by said dynode unit as a signal; a pair of insulating support members holding unitedly said dynode unit and said anode in a state grasping said dynode unit and said anode; a focusing electrode arranged between said photocathode and said dynode unit, and having a through hole through which the photoelectrons from said photocathode pass, said focusing electrode correcting an orbit of each photoelectron emitted from said photocathode; and an accelerating electrode arranged between said focusing electrode and said dynode unit, and having a through hole through which the photoelectrons reached from said photocathode via said focusing electrode pass, said accelerating electrode accelerating the photoelectrons reached from said photocathode via said focusing electrode, wherein each of said pair of insulating support members has a main body attached with each one end of at least said first and second dynodes, and at least two protruding portions extending from said main body toward said photocathode and arranged so as to sandwich each part of said focusing electrode and said accelerating electrode, thereby serving as a reference of alignment positions of said focusing electrode and said accelerating electrode, and wherein each of said protruding portions has a first fixture structure fixing said accelerating electrode in a state supporting directly said accelerating electrode, and a second fixture structure fixing said focusing electrode in a state supporting directly said focusing electrode.