Detector types scintillation counter

The basic function of the spectrometer is to separate the polychromatic beam of radiation coming from the specimen in order that the intensities of each individual characteristic line can be measured. In principle, the wide variety of instruments (WDXRF and EDXRF types) differ only in the type of source used for excitation, the number of elements which they are able to measure at one time and the speed of data collection. Detectors commonly employed in X-ray spectrometers are usually either a gas-flow proportional counter for heavier elements/soft X-rays (useful range E < 6keV 1.5-50 A), a scintillation counter for lighter elements/hard X-rays (E > 6keV 0.2-2 A) or a solid-state detector (0.5-8 A). 

In order to assess the accuracy of the present method, we compared it with two other methods. One was the Track Etch detector manufactured by the Terradex Corp. (type SF). Simultaneous measurements with our detectors and the Terradex detectors in 207 locations were made over 10 months. The correlation coefficient between radon concentrations derived from these methods was 0.875, but the mean value by the Terradex method was about twice that by our detectors. The other method used was the passive integrated detector using activated charcoal which is in a canister (Iwata, 1986). After 24 hour exposure, the amount of radon absorbed in the charcoal was measured with Nal (Tl) scintillation counter. The method was calibrated with the grab sampling method using activated charcoal in the coolant and cross-calibrated with other methods. Measurements for comparison with the bare track detector were made in 57 indoor locations. The correlation coefficient between the results by the two methods was 0.323. In the case of comparisons in five locations where frequent measurements with the charcoal method were made or where the radon concentration was approximately constant, the correlation coefficient was 0.996 and mean value by the charcoal method was higher by only 12% than that by the present method. 

There are two possibilities for the detection of the interferences the film detection and the registration of x-ray counts with scintillation counters or position-sensitive detectors. However, the SAXD method does not detect interferences from which the interlayer spacings can be calculated. It rather makes it possible from the sequence of the interferences to decide the type of liquid crystal [13,14]. 

Radioactivity of uranium can be measured by alpha counters. The metal is digested in nitric acid. Alpha activity is measured by a counting instrument, such as an alpha scintillation counter or gas-flow proportional counter. Uranium may be separated from the other radioactive substances by radiochemical methods. The metal or its compound(s) is first dissolved. Uranium is coprecipitated with ferric hydroxide. Precipitate is dissolved in an acid and the solution passed through an anion exchange column. Uranium is eluted with dilute hydrochloric acid. The solution is evaporated to near dryness. Uranium is converted to its nitrate and alpha activity is counted. Alternatively, uranium is separated and electrodeposited onto a stainless steel disk and alpha particles counted by alpha pulse height analysis using a silicon surface barrier detector, a semiconductor particle-type detector. 

All methods of radiometric analysis involve, of course, the use. of various radiation detection devices, The devices available for measuring radioactivity will vary with the types of radiations emitted by the radioisotope and the kinds of radioactive material. Ionization chambers are used for gases Geiger-Miiller and proportional counters for solids liquid scintillation counters for liquids and solutions and solid crystal or semi-conductor detector scintillation counters for liquids and solids emitting high-energy radiations. Each device can be adopted to detect and measure radioactive material in another state, e.g., solids can be assayed in an ionization chamber. The radiations interact with the detector to produce a signal,... 

Many nuclear processes occui one after the other within a very short time of the order of picoseconds or less - for instance a. or fi decay followed by y-ray emission or emission of a cascade of y rays. The events are practically coincident, and for many purposes it is of interest to know whether two particles or photons are emitted practically at the same time or not. For detection and measurement of coincident events two detectors and a coincidence circuit are used. The detectors are chosen according to the coincidences to be measured, e.g. ot-y, fi y, y-y, X-y, y5-e or other types of coincidences, and the coincidence circuit records only events occurring within a given short time interval. Scintillation counters and semiconductor detectors are commonly used for these measurements. 

Canberra well-type HPGe gamma detector for determination of Sr Liquid scintillation counter (Wallac 1220) for determination of... 

The 4jt P-y coincidence counting is an improved version of the P y coincidence counting method. Here, a 4ji p gas flow type proportional counter is usually used as the P-detector, and a Nal(Tl) scintillation counter located near the 4tc P counter wall is employed to detect the y-rays. 

A solvent module (Varian model No. 5000) with a UV detector coupled to an on-line Nal(Tl) detector was used for high performance liquid chromatography (HPLC) analysis. For radioactive measurements, a dose calibrator (Capintec CRC-7, USA), a solid scintillation counter (ORTEC, USA) with a plane (7.62 cm x 7.62 cm) Nal(Tl) detector, an automatic well type gamma counter (Compac-120, Picker, USA) and a multichannel analyser coupled to a Nal(Tl) detector (7.62 cm x 7.62 cm) were used. 

The fourth detector system is to use a resonance scintillation counter [57]. A standard type of plastic scintillator for /5-detection is doped with the resonant absorber. It is insensitive to the non-resonant background of primary... 

Cosmic rays, which are highly energetic charged particles, produce background in all types of detectors, and scintillators are no exception. The effect of cosmic-ray background, as well as that of the other sources mentioned earlier, will be reduced if two counters are used in coincidence or anticoincidence. 

For Ge detectors other than the well-type, the efficiency is low, relative to Na(Tl) scintillation counters. This statement holds true for Si(Li) detectors as well (see Sec. 12.9). Lower efficiency, however, is more than compensated for by the better energy resolution of the semiconductor detector. Figure 12.32 illustrates the outstanding resolution characteristics of a semiconductor detector by showing the same spectrum obtained with a Nal(Tl) and a Ge(Li) detector. Notice the tremendous difference in the FWHM. The Ge(Li) gives a FWHM =... 

The width F is indicated as electronic noise in Fig. 12.41. Of the three types of X-ray detectors mentioned—scintillation, proportional, and semiconductor counters—the Si(Li) detector has the best energy resolution for X-rays. This fact is demonstrated in Fig. 12.42, which shows the same energy peak obtained with the three different detectors. Notice that only the Si(Li) detector can resolve and lines, an ability absolutely necessary for the study of fluorescent X-rays for most elements above oxygen. The manganese fluorescence spectrum obtained with a Si(Li) detector is shown in Fig. 12.43... 

Scintillation counters and germanium detectors are two types of sophisticated nuclear radiation detectors which depend upon the interaction of radiation with solid materials, such as Nal (Tl) crystals or germanium solid state diodes. They have the ability to distinguish the energies of the radiation and have a higher sensitivity to radiation than the materials discussed heretofore. They also require sophisticated instrumentation associated with their use and are expensive. 

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. 

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. 

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