The oil light-couple is necessary to obtain an intimate connection of the phosphor with the photomultiplier to ensure the efficient passage of very small light photons. VOSE, in Introduction to Nuclear Techniques in Agronomy and Plant Biology, 1980 Detector Systems for Scintillation CountingĪ scintillation detector consists of a crystal or other phosphor coupled with its mount to a PM tube with a silicone oil light-couple. These crystals offer a good transparency, high photon efficiency and can be produced in large sizes. For X-ray detectors, in most cases NaI or CsI crystals activated with thallium are used. The average energy necessary to produce one electron at the photocathode is approximately 300 eV. At the detector output an electric pulse proportional to the absorbed energy is produced. Electrons, emitted from the photocathode, are accelerated by the applied high voltage and amplified at the dynodes of the attached photomultiplier ( Figure 3). The light pulses are collected by a photo- cathode. The number of photons produced is proportional to the energy of the absorbed primary photon. In scintillation detectors the material of the detector is excited to luminescence (emission of visible or near-visible light photons) by the absorbed photons or particles. Scintillation detectors are used for the determination of the high-energy part of the X-ray spectrum. Utz Kramar, in Encyclopedia of Spectroscopy and Spectrometry, 1999 Scintillation detectors
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