Open counter for low energy electron detection with suppressed background noise

摘要

A photoelectron counter in an open detection chamber in which photoelectrons emitted from a solid surface by a photon irradiation energy are counted, is arranged so as to suppress background noise which produces a false count rate due to photoelectrons which are emitted from solid surfaces outside the subject when scattered rays have reached and irradiated the same surface. The counter uses one or more of options including a film or coating formed with a thickness which is less than several mu m thickness on parts which are subject to scattered rays incident from the subject, a ray screen for interrupting scattered rays from entering into the detection chamber and/or a center guard provided at the front part of the detector to enable nearby measurement and while interrupting scattered rays.