| 摘要 |
An improved large area self-powered photon detector (hereafter referred to by the acronym LASPPD) based monitor of the movement of photon sources into and out of radiographic source shields is described. The term photon shall be used throughout this application to denote x-rays or gamma rays. The photon source position monitor system comprises: a photon sensitive electrode assembly; a current-to-voltage converter-amplifier that is electrically connected to the electrode assembly; an analog logic circuit coupled to output of the current-to-voltage converter-amplifier; an integrated circuit for controlling the on/off state of an annunciator; an alarm annunciator; a direct current power source and a metallic enclosure that encompasses the electrode, the signal conditioning electronics, analog logic circuit, direct current power source, integrated circuit, and alarm annunciator. When the photon source is driven out of its shield past the LASPPD based monitor positioned proximate the source egress/ingress conduit of the shield, the photons emitted by the source interact with the electrode of the monitor. The photons interacting with the electrode generate a current that is amplified and conditioned such that it can be used to activate an annunciator that remains in an active condition until the source is retracted back into the shield past the monitor. The device provides a radiographic technologist with an active alarm that indicates the position of a radioactive source during radiographic inspections of industrial components.
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