Photomultiplier tube tightly arranged with substantially no space between adjacent tubes

Abstract

A photomultiplier tube unit including photomultiplier tubes densely assembled and thereby having an improved light sensing efficiency. The outer surfaces ( b) of metal side tubes ( ) of photomultiplier tubes ( ) are in facial contact with one another, and thereby a high-density arrangement of photomultiplier tubes ( ) are achieved. The side tubes ( ) can be electrically connected to one another, and therefore the side tubes ( ) can be easily made equipotential. As a result, it is unnecessary to electrically connect the stem pin ( ) to the side tube ( ) of each photomultiplier tube ( ), facilitating the assembling of the photomultiplier tube unit. When a required photomultiplier tube ( ) in a device (e.g., a gamma camera) having thus-united multiple photomultiplier tubes is replaced with a new one, the troublesome work of replacing photomultiplier tubes one by one is obviated, simplifying the replacement work.