US Patent 7135670 Photomultiplier and radiation detector

Onto a base member, through which stem pins are passed and holding members are to be joined to the respective surfaces thereof, the stem pins and the holding members are joined by fusion by melting of the base member to arrange a stem with at least three or more layers formed by sandwiching the base member by the holding members. In comparison to a conventional arrangement wherein the stem is arranged as a single layer of glass material and this is melted to fuse the stem pins, the positional precision, flatness, and levelness of both surfaces of the stem are improved.