Patent ID: 7923929
Filing Date: 2011-04-12
Classification: H01J

Abstract:
1. 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 plurality of stages of dynodes being constituted by at least a first-stage dynode which the photoelectrons from said photocathode initially reach and a second-stage dynode receiving the secondary electrons outputted from said first-stage dynode in response to the reached photoelectrons; 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, for accelerating the photoelectrons reached from said photocathode via said focusing 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 being set to a potential higher than that of said first-stage dynode, wherein each of said pair of insulating support members has a portion directly gripping said accelerating electrode together with said dynode unit in a state that at least said first-stage dynode and said second-stage dynode included in said dynode unit are directly opposite to said accelerating electrode not connected through a conductive member, whereby a position variation of said accelerating electrode with respect to said dynode unit is restricted in both of a first direction extending from said photocathode to said dynode unit and a second direction orthogonal to the first direction.