Patent ID: 7649163

Claim:
A photomultiplier tube module comprising: a photomultiplier tube which is fixed in a housing, whose light incident surface is arranged on a side of a front surface of said housing, and an extension line of a tube axis of which is provided a position displaced from a center of gravity position of said front surface; a high-voltage generating circuit board which is fixed in said housing, whose board surface is arranged so as to intersect the extension line of the tube axis, and which applies an operating voltage to said photomultiplier tube; a signal processing board which is fixed in said housing and located on a side opposite to a direction toward the tube axis from the center of gravity position, whose one end portion is adjacent to a tube wall of said photomultiplier tube, whose board surface is parallel to the tube axis, and which processes an output signal of said photomultiplier tube that flows in from a region on a side of the one-end portion; and a digital circuit which is provided on an outside surface of said signal processing board located on a side opposite to an inside surface opposed to said photomultiplier tube and which digitally processes an output signal from said photomultiplier tube, wherein said high-voltage generating circuit board is provided on said inside surface of said signal processing board; said digital circuit comprises a comparator in which an output signal of said photomultiplier tube is inputted and a signal processor that outputs a digital value according to a number of square waves outputted from said comparator; and said comparator and said signal processor are arranged on other end portion opposite to said one end portion of said signal processing board.