Читать книгу Patty's Industrial Hygiene, Physical and Biological Agents - Группа авторов - Страница 51

A scintillation detector is a transducer that converts the energy of the radiation into a flash of light, which is then converted by a photomultiplier into a voltage pulse. Whereas the inherent gamma ray detection efficiency of G–M counters is very low, usually less than 1%, the gamma ray detection efficiency of solid scintillation detectors is very high. Thus, a scintillation detector is extremely sensitive for detecting gamma radiation as compared to a gas filled G–M detector. Furthermore, since the intensity of the flash of light in the scintillation detector is proportional to the energy of the incident radiation, a scintillation counter can, with the aid of the proper electronics, be used to distinguish among various gamma ray energies. Using this principle, scintillation survey meters are available that can be used to identify the gamma‐emitting isotope. The resolving time of a scintillation detector is much less than that of a G–M counter. Scintillation detectors therefore can be used in higher radiation fields than G–M counters. However, in return for these advantages, scintillation detectors are relatively expensive and relatively fragile as well as being temperature dependent. Because of its high gamma ray sensitivity, the typical scintillation survey meter has a full‐scale response of 0.02 mrad h⁻¹ (from ¹³⁷Cs or ⁶⁰Co). Like G–M counters, scintillation detectors generally are not designed for measuring dose. Table 4 identifies the best applications for some of the more common scintillation detectors and for G–M detectors in general. Typical portable scintillation detectors for contamination control include ZnS(Ag) and NaI(Tl) crystals.