Patent ID: 7276704

Claim:
A photomultiplier tube, comprising: a faceplate for receiving light incident thereon; a photocathode for emitting electrons in response to the light incident on the faceplate; a hermetically sealed vessel; an electron multiplier provided in the hermetically sealed vessel for multiplying electrons emitted from the photocathode; and an anode for generating an output signal based on electrons multiplied by the electron multiplier, wherein the hermetically sealed vessel includes: a stem plate having a main surface having stem pins for fixing the electron multiplier and the anode thereon; a metal side tube having an outer side wall extending along a tube axis, an inner side wall opposing the outer side wall, and two open ends for enclosing the electron multiplier and the anode, one of the open ends being fixed and sealed to the stem plate; and the faceplate having two main surfaces, one of the main surfaces of the faceplate receiving the light incident thereon, the other open end of the metal side tube being sealed with the other of the main surfaces of the faceplate, the faceplate being made from glass, the metal side tube having an edge portion on a peripheral portion of the other open end, the peripheral portion being embedded in the other main surface of the faceplate with the edge portion being directly intimate with the faceplate with no member intervened therebetween, the edge portion having a tip end oriented toward the tube axis, wherein a distance between the tip end and the inner side wall in a direction perpendicular to the tube axis is shorter than a distance between the outer side wall and the inner side wall.