Sodium iodide scintillator

Before injection, monitoring probes re placed on the outlet lines close a the exit from the tank being tested. These probes consist of a l-in.-diarr.-tter, thalium-activated sodium-iodide scintillation crystal, a small portable meter, and a recorder. 

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... 

An additional potential means of surveying the deposited material following the passage of a radioactive plume is by using an aircraft instrumented with a sodium iodide scintillation counter which can detect y-radiation in different wavebands and hence... 

Fig. 117. Sodium iodide scintillation counter with ring-beaker arrangement for measurement of gamma emitters directly from the water sample...

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). 

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... 

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