Scintillation crystal detectors

Scintillation counting Scintillation crystals Scintillation detector Scintillation detectors... 

In both scintillator and gas detectors, the absorption of radiation causes excitation and ionization however with the scintillation process, the absorbed energy produces a flash of light, rather than a pulse of current. The principal types of scintillation detectors found in the clinical chemistry laboratory are the sodium iodide crystal scintillation detector and the organic liquid scintillation detector. Because of the crystal detector s relative ease of operation and economy of sample preparation, most clinical laboratory procedures have been developed to measure nucfides, such as which can be counted efficiently in a crystal detector. A liquid scintillation detector is used to measure pure (3-emitters, such as tritium or C. 

Crystal Scintillation Detector. The well detector is a common type of a crystal scintillation detector and has a hole drilled in the end or side of the cylindrical crystal to accept a test tube. Because it is hygroscopic, the crystal is hermetically sealed in an aluminum can with a transparent quartz window at one end through which the blue-violet (420 nm) scintillations are detected. The photons of gamma emitters, such as Cr, Co, Fe, and (Table 1-14) in the sample easily penetrate the specimen tube and the thin, low-density can and enter the crystal where they are likely to... 

Melcher CL (1990) Lutetium orthosilicate single crystal scintillator detector. US Patent 4,958,080 MMC Magnetics, http //www.mmcmagnetics.com/ourproducts/main SmCohtm. Accessed Dec 2014... 

Scintillation detectors are substances which fluoresce when stmck by x-radiation. Scintillation can, therefore, serve to convert x-ray photons into visible or ultraviolet light. Scintillation materials include thaUium-activatedcrystals of sodium iodide, NaI(Tl), potassium iodide, KI(T1), or cesium iodide, CsI(Tl) crystals of stilbene (a, P-diphenylethylene) [588-59-0] and anthracene [120-12-7] bismuth germanium oxide [12233-56-6] ... 

The activation [672] of Lil with Eu2+ and the use of an activated Lil phosphor as a scintillation detector for slow neutron detection [673] has been investigated. Blue, fluorescent Lil (0.03 mole % Eu) phosphor was found to be the most useful [673] phosphor because of its ease to growth, relatively high light output, chemical stability and good match with spectral characteristics of the 6260 type photomultiplier. Lil (Eu), however, does have an interfering y radiation sensitivity. Fast neutron scintillation spectra of Li6(w, a)H3 in Eu doped Lil crystals has also been investigated [674]. 

Another commonly used detector is the scintillation detector. This makes use of a crystal that produces a scintillation (pulse of visible light) upon absorption of an x-ray photon. The visible light is detected by a photomultiplier tube and associated amplifier circuit, which is sensitive enough to detect nearly every scintillation. The scintillating crystal is usually sodium iodide doped with an activator such as thallous iodide. 

Figure 10.10. A typical scintillation detector. (Well crystal Nal)...

Scintillation detectors with Nal(Tl) crystals may also be used for y spectrometry. Because Nal(Tl) crystals can be made in larger size than Ge crystals and because the atomic number of I is larger than that of Ge, the internal counting efficiency of Nal(Tl) detectors for y rays is higher than that of Ge crystals, as already discussed in section 7.5 (Fig. 7.16). On the other hand, the energy resolution is appreciably lower (5 to 7% for y energies of the order of 100 keV). Scintillation detectors are operated in a way similar to that used with Ge detectors, but without cooling. 

Gas-filled detectors are used for X-rays or low energy gamma rays. These include ionization chambers, proportional counters and Geiger-Miiller counters. Scintillation detectors are used in conjunction with a photomultiplier tube to convert the scintillation light pulse into an electric pulse. Solid crystal scintillators such as Csl or Nal are commonly used, as well as plastics and various liquids. 

Figure 3.13. The overall view of the goniostat of the Rigaku TTRAX rotating anode powder diffractometer with the horizontal goniometer axis, and synchronized rotations of both the x-ray source and detector arms. This goniometer is equipped with variable divergence, scatter and receiving slits, curved crystal monochromator, and scintillation detector. (Courtesy of Rigaku/MSC.)...

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