Patent ID: 7659666

Claim:
A photomultiplier comprising: a sealed container including a hollow body section extending along a predetermined tube axis, and a faceplate provided so as to intersect the tube axis and transmitting light with a predetermined wavelength; a photocathode provided inside sealed container so as to emit photoelectrons into said sealed container in response to incidence of the light with the predetermined wavelength; a dynode unit provided inside the sealed container so as to cascade-multiply photoelectrons emitted from said photocathode, said dynode unit including: at least one dynode set constituted by a plurality of dynodes that respectively have a secondary electron emitting surface; and a pair of insulating supporting members clampingly and integrally holding said one dynode set; and a gain control unit for controlling a gain of at least one electron multiplier channel formed by said one dynode set, wherein said gain control unit has: an insulating base plate having fixing tabs provided at opposite ends thereof, the opposite ends of said insulating base plate being clamped by said pair of insulating supporting members by each of said fixing tabs being inserted into an associated one of fixing slits respectively provided on said pair of said insulating supporting members, whereby said insulating base plate is in direct contact with both of said insulating supporting members paired; a control dynode, fixed to said insulating base plate, belonging to said one dynode set, said control dynode controlling the gain of the electron multiplier channel by adjustment of a setting potential; an anode, fixed to said insulating base plate, for capturing secondary electrons cascade-multiplied by said electron multiplier channel, said anode being set to a higher potential than any of the dynodes of said one dynode set; and a final stage dynode, fixed to said insulating base plate at a position where secondary electrons that have passed through said anode arrive, belonging to said one dynode set, said final dynode reversing the secondary electrons that have passed through said anode back to said anode.