Sodium iodide scintillation detector

Tracer injection is performed by injecting a suitable tracer via the tracer injector described above and monitoring the output from the vessel by means of a sodium iodide scintillation detector. 

The expts were conducted in stainless steel sigma-blade type mixers with proplnt mixing capacities of 60, 600 and 2000 lbs, respectively. Radioactivity measurements on samples taken from various locations in the batch at different mixing times were performed with a sodium iodide scintillation detector system... 

The function of the X-ray counter is to measure the intensity of the diffracted X-ray beam and to provide output pulses that are proportional in height to the energy of the detected photon. This provides a means of discriminating against multiple-order interferences by pulse height analysis. Multiple-order interferences are fluorescence X-rays with 1/2, 1/3, 1/4 of the wavelength of interest in compliance with = 2, 3, 4 in the Bragg equation. Two types of counter are normally used on WD-XFR spectrometers, gas proportional counters and sodium iodide scintillation detectors. 

With a resolution of 7-10% the sodium iodide scintillation detector offers inferior discrimination, but detectors are available with much higher detection efficiencies than are possible with high-resolution detectors. The detection of 7-rays is based on scintillations produced in the thallium-activated sodium iodide crystal and observed by a photomultiplier tube, operating efficiently at ambient temperature. 

Relative efficiency is a general performance measure relating the efficiency of detection of the Co gamma-ray at 1332 keV of the detector to that of a standard sodium iodide scintillation detector (this is discussed further in Chapter 11, Section 11.4.3). 

The gamma ray scintillation spectrometer (Fig. 1) consisted of two single channel analyzers coupled to a common sodium iodide well detector, preamplifier, amplifier and scalers. By setting each analyzer for the appropriate energy the two isotopes were determined. 

The most commonly used isotopic labels for such assays are 1-125, Co-57, H-3, and C-14. However, since 1-125 and Co-57 are gamma emitters, while H-3 and C-14 are beta emitters, two basically different types of nuclear counting equipment are required to detect both types of radiation. These gamma emitters are most conveniently counted with a sodium iodide well detector, while beta emitters must be detected in a liquid scintillation counter. 

Scintillators which have hydrogen as a constituent, such as organic liquids for example, may be used for fast neutron detection, since the protons produced by fast neutron collisions create the ionization required to operate the detector. In order to adapt a sodium iodide scintillator for the detection of slow neutrons, a small concentration of boron may be distributed in the crystal, giving a particles on neutron capture as discussed above. Alternatively, it is possible to add a neutron absorber which emits 7 rays following the (n, y) capture reaction. Another possibility is the use of lithium iodide (Lil) which, in addition to its own suitability as a scintillator, interacts with neutrons through the reaction... 

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 equipment used in gamma spectroscopy includes a detector, a pulse sorter (multichannel analyzer), and associated amplifiers and data readout devices. The detector is normally a sodium iodide (Nal) scintillation counter. Figure 27 shows a block diagram of a gamma spectrometer. 

As discussed above, the measurement of characteristic y rays is very similar to the methods used in EDXRF. Early studies used a scintillation counter, typically a crystal of sodium iodide containing a small amount of thallium (Tite 1972). y ray absorption by these counters produces visible light, which is converted into an electrical pulse using a photosensitive detector. More recently semiconductor detectors have been used, either a lithium drifted germanium crystal, or, more typically, a pure ( intrinsic )... 

A range of scintillants is available, many designed for maximum efficiency with specific isotopes. Crystals of sodium iodide containing a small amount of thallous iodide are very efficient detectors of gamma radiation and... 

Alpha-particle detector Beta-particle detector Gamma-ray detector proportional counters silicon (Si) diode with spectrometer proportional counters Geiger-Muller counters liquid scintillation (LS) counters thallium-activated sodium iodide (Nal(Tl) detector with spectrometer germanium (Ge) detector with spectrometer... 

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. 

Solid scintillators include materials such as sodium iodide, lithium iodide, anthracene, naphthalene and loaded polymers. Sodium iodide detectors are by far the most important, and subsequent discussions will be restricted to... 

Scintillation counters usually consist of a sodium iodide crystal doped with 1% thallium. The incident X-ray photons cause the crystal to fluoresce producing a flash of light for every photon absorbed. The size of the light pulse is proportional to the energy of the photon and is measured by a photomultiplier. A deficiency associated with scintillation counters is that they do not provide as good energy resolution as proportional or solid state 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. 

These are used on single counter four-circle diffractometers. The detector is often sodium iodide. The scintillator is used in conjunction with a photomultiplier tube. Thallium activated sodium iodide has an energy resolution of about 40% at lOkeV. Hence, the attractiveness of such a detector lies not only with its counting of individual photons but also its... 

---