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Proportional and Scintillation Counters

Electronic counters are devices in which absorption of an x-ray photon or a neutron generates a short electric pulse in the associated electronic circuitry. By counting the rate of generation of such pulses, the flux of the x-ray or neutron beam to which the device is exposed can be measured. These counters are the outgrowth of the initial efforts made by nuclear physicists for detection of radioactivities of materials. Most useful among them for x-ray and neutron scattering studies are the proportional and scintillation counters described in Section 2.4.1. Further elaboration on these counters led to the development of position-sensitive detectors, explained in Section 2.4.2. Very recently, a number of novel devices based on new technologies have become available, and these are briefly introduced in Section 2.4.4. [Pg.57]

Avoiding a loss of intensity by absorption, XRF analysis is realized under vacuum. The intensities of the fluorescence radiation are measured by flow or sealed proportional and scintillation counters. For quantification, measured intensities are compared with intensities of known standard samples. Based on the measured raw intensities, element concentrations are calculated using the... [Pg.187]

In view of their complementary sensitivity characteristics, proportional and scintillation counters are... [Pg.5131]

Detector, flow proportional, or scintillation, or flow proportional and scintillation counter. [Pg.748]

The analyzing magnet in conjunction with the multi-wire proportional chamber planes, was used to measure the momenta of charged particles. The shower counters and scintillation counters, installed after the iron absorbers, identified electrons and muons accordingly. After the introduction of a set of criteria, 320 examples of the decay (1) were observed. By imposing more strict criteria, from this number, 163 events were selected [3],... [Pg.227]

Four types of counters are currently in use proportional, Geiger, scintillation, and semiconductor. All depend on the power of x-rays to ionize atoms, whether they are atoms of a gas (proportional and Geiger counters) or atoms of a solid (scintillation and semiconductor counters). A general treatment of the first three types has been given by Parrish [7.8]. [Pg.199]

As in the proportional counter, the pulses produced in a scintillation counter have sizes proportional to the energy of the x-ray quanta absorbed. But the pulse size corresponding to a certain quantum energy is much less sharply defined, as shown in Fig. 7-19 for typical proportional and scintillation (Nal Tl) counters. As a result, it is more difficult to discriminate, with a scintillation counter, between x-ray quanta of different wavelengths (energies) on the basis of pulse size. [Pg.209]

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... [Pg.420]

Energetic electrons cause ionization and molecular excitation in matter, although the effect is weaker and more difficult to detect than for a-particles. As a result the effect must be amplified for coimting individual /3-particles. Ionization is used in proportional and Geiger counters. Scintillation counting can also be used with various detector systems (Ch. 8). [Pg.63]

SECTIONS 21.4 AND 21.5 The SI unit for the activity of a radioactive source is the becquerel (Bq), defined as one nuclear disintegration per second. A related unit, the curie (Ci), corresponds to 3.7 X 10 disintegrations per second. Nuclear decay is a first-order process. The decay rate (activity) is therefore proportional to the number of radioactive nuclei. The half-life of a radionuclide, which is a constant, is the time needed for one-half of the nuclei to decay. Some radioisotopes can be used to date objects C, for example, is used to date organic objects. Geiger counters and scintillation counters count the emissions from radioactive samples. The ease of detection of radioisotopes also permits their use as radiolracers to follow elements through reactions. [Pg.908]

In X-ray fluorescence spectrometry, primary X-ray radiation is produced by means of an X-ray tube, exciting the sample located in this beam to emit fluorescence. This secondary radiation is rendered parallel by a collimator and diffracted and reflected by a movable analyzer crystal. The intensity of the radiation is measured in the receiver, e.g. a geiger, proportional or scintillation counter, at a wavelength specific to the element. [Pg.102]

Proportional counters and scintillation counters are used as detectors. The proportional counters should preferably be designed without windows and take the form of methane flow counters, ce-rays generally feature extremely high energy levels of several MeV, but only a very limited range. Water can thus not be measured directly, and instead it is necessary to achieve a concentration of Oi -emitting nuclides, with particular attention being paid to radium 226, but also to uranium and thorium. [Pg.446]

WDXRF systems commonly use one or more of the following detectors gas flow proportional counter (flow counter [FC]), sealed gas-proportional counter, and scintillation counters (SC). [Pg.637]

Multiple proportional counters are used in simultaneous X-ray spectrometers, described later, while one proportional counter is often used in tandem with an SC in a sequential system. It is for this reason that the detector has two windows as shown in Figure 8.38. X-ray photons pass through the proportional counter to the SC located behind it, as illustrated in Figure 8.31, and signals are obtained from both detectors. It should be noted that this tandem arrangement does not permit independent optimization of both detectors. There are sequential spectrometer systems available with independent proportional and scintillation detectors. [Pg.641]

How do Geiger counters and scintillation counters measure radioactivity Precisely, what do they count Do they count radiations or do they count something that is proportional to radiation Suggest units for radioactivity as it would be measured by either of these counters. [Pg.595]

Figure 8.28 shows how the X-rays fall on the solid or liquid sample which then emits X-ray fluorescence in the region 0.2-20 A. The fluorescence is dispersed by a flat crystal, often of lithium fluoride, which acts as a diffraction grating (rather like the quartz crystal in the X-ray monochromator in Figure 8.3). The fluorescence may be detected by a scintillation counter, a semiconductor detector or a gas flow proportional detector in which the X-rays ionize a gas such as argon and the resulting ions are counted. Figure 8.28 shows how the X-rays fall on the solid or liquid sample which then emits X-ray fluorescence in the region 0.2-20 A. The fluorescence is dispersed by a flat crystal, often of lithium fluoride, which acts as a diffraction grating (rather like the quartz crystal in the X-ray monochromator in Figure 8.3). The fluorescence may be detected by a scintillation counter, a semiconductor detector or a gas flow proportional detector in which the X-rays ionize a gas such as argon and the resulting ions are counted.
In X-Ray Fluorescence (XRF), an X-ray beam is used to irradiate a specimen, and the emitted fluorescent X rays are analyzed with a crystal spectrometer and scintillation or proportional counter. The fluorescent radiation normally is diffracted by a crystal at different angles to separate the X-ray wavelengths and therefore to identify the elements concentrations are determined from the peak intensities. For thin films XRF intensity-composition-thickness equations derived from first principles are used for the precision determination of composition and thickness. This can be done also for each individual layer of multiple-layer films. [Pg.26]

At present, the Geiger counter is the most popular x-ray detector in analytical chemistry. Although it is yielding ground to the proportional counter and the scintillation counter, it will be remembered for having greatly accelerated the use of x-ray emission spectrography in analytical chemistry. [Pg.52]

In the phosphor-photoelectric detector used as just described, the x-ray quanta strike the phosphor at a rate so great that the quanta of visible light are never resolved they are integrated into a beam of visible light the intensity of which is measured by the multiplier phototube. In the scintillation counters usual in analytical chemistry, on the other hand, individual x-ray quanta can be absorbed by a single crystal highly transparent to light (for example, an alkali halide crystal with thallium as activator), and the resultant visible scintillations can produce an output pulse of electrons from the multiplier phototube. The pulses can be counted as were the pulses-from the proportional counter. [Pg.59]

Recent papers from the Philips Laboratories37 40 contain thorough discussions of the Geiger counter, the proportional counter, and the scintillation counter, and significant performance data for all three, the emphasis being placed throughout upon x-ray applications. The detection system employed by Parrish and Kohler was particularly noteworthy in that it could conveniently accommodate any one of four detectors. ... [Pg.65]

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). [Pg.629]

Lekner, 1967 Lekner and Cohen, 1967). From the experimental viewpoint, LRGs are excellent materials for the operation of ionization chambers, scintillation counters, and proportional counters on account of their high density, high electron mobility, and large free-ion yield (Kubota et al., 1978 Doke, 1981). Since the probability of free-ion formation is intimately related to the thermalization distance in any model (see Chapter 9), at least a qualitative understanding of electron thermalization process is necessary in the LRG. [Pg.279]


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