The Scintillation Method

Measurement of Clinical Radioactivity.

“…Besides having high stopping power, this material produces generous amounts of light to which the crystal itself is transparent (as it must be), and the blue-violet light is well suited to many good phototubes. Sodium iodide is a medium-speed scintillator, 10 which means that whereas it is fast enough to permit high counting rates, it does not unduly complicate the design of the processing circuitry.…”

The nuclear decays of Zr97 and Nb97

“…Statistical fluctuations in the number of photons created in the scintillator by the radiation, in the number of these photons transmitted to the phototube, and in the photoelectric detection of these photons at the photocathode of the phototube limit the resolution attain able with scintillators. Resolution of about 8% at 1 MeV ((full-width-at-half-maximum)/(peak energy)) is typical for a compared to about 500 eV (se^) for an average photoelectron at the cathode of a scintillator's photomultiplier (19). The corresponding numbers of electron-hole pairs and photoelectrons produced by a nuclear particle of energy E are then just and K/e^.…”

“…The corresponding numbers of electron-hole pairs and photoelectrons produced by a nuclear particle of energy E are then just and K/e^. Since the statistical fluctuations in these numbers are roughly proportional to the square roots of the numbers (19), the resolution of semiconductor detectors is at least an order of magnitude higher than that of scintillators. For both kinds of detectors the use of high atomic number (Z) materials is advantageous for gamma-ray detection (the cross-section for the photoelectric effect -the kind of interaction most likely to lead to complete absorption of 5 a gamma ray -goes as Z ); salts of iodine (most commonly, Nal) provide hi^h-X scintillators, and germanium is used for semiconductor detectors (principally because no satis factory semiconductors of higher 7, have been found) .…”

The nuclear decays of Zr97 and Nb97

“…The corresponding numbers of electron-hole pairs and photoelectrons produced by a nuclear particle of energy E are then just and K/e^. Since the statistical fluctuations in these numbers are roughly proportional to the square roots of the numbers (19), the resolution of semiconductor detectors is at least an order of magnitude higher than that of scintillators.…”

“…The most commonly used materials are inorganic (e.g., thallium-activated sodium iodideNal (Tl)) and organic (plastics, anthracene, stilbene) crystals. compared to about 500 eV (se^) for an average photoelectron at the cathode of a scintillator's photomultiplier (19). The corresponding numbers of electron-hole pairs and photoelectrons produced by a nuclear particle of energy E are then just and K/e^.…”