Radiation counters

Use Neutron counter, radiation shielding (in the form of boral), medicine. 

Figure 23.18 Schematic diagram of a Geiger counter. Radiation (a, p, or y rays) entering through the window ionized the argon gas to generate a smaii current flow between the eiectrodes. This current is ampiifled and is used to flash a tight or operate a counter with a ciicking sound.

Dosimeters Monitor radiation dose to field personnel and first responders Ionization chamber Geiger-Muller counter Radiation-sensitive film Semiconductor detector... 

In a Geiger counter, radiation produces charged particles in the gas contained in a tube, which generates an electrical current. 

It was found that that in the case of soft beta and X-ray radiation the IPs behave as an ideal gas counter with the 100% absorption efficiency if they are exposed in the middle of exposure range ( 10 to 10 photons/ pixel area) and that the relative uncertainty in measured intensity is determined primarily by the quantum fluctuations of the incident radiation (1). The thermal neutron absorption efficiency of the present available Gd doped IP-Neutron Detectors (IP-NDs) was found to be 53% and 69%, depending on the thicknes of the doped phosphor layer ( 85pm and 135 pm respectively). No substantial deviation in the IP response with the spatial variation over the surface of the IP was found, when irradiated by the homogeneous field of X-rays or neutrons and deviations were dominated by the incident radiation statistics (1). 

With the help of Geiger counter the p- and y-radiations are registered. 

There are many types of electronic detector. The original fomi of electronic detector was the Geiger counter, but it was replaced many years ago by the proportional counter, which allows selection of radiation of a particular type or energy. Proportional counters for x-rays are filled witii a gas such as xenon, and those for... 

Liquid scintillation counting is by far the most common method of detection and quantitation of -emission (12). This technique involves the conversion of the emitted P-radiation into light by a solution of a mixture of fluorescent materials or fluors, called the Hquid scintillation cocktail. The sensitive detection of this light is affected by a pair of matched photomultiplier tubes (see Photodetectors) in the dark chamber. This signal is amplified, measured, and recorded by the Hquid scintillation counter. Efficiencies of detection are typically 25—60% for tritium >90% for and P and... 

The high cross-section for thermal neutrons results in the use of boron and boron compounds for radiation shielding (14). The ease of detecting the a-particle produced when boron absorbs thermal neutrons results in the use of boron for neutron counters as weU. 

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. 

XRD is an excellenr, nondestructive method for identifying phases and characterizing the structural properties of thin films and multilayers. It is inexpensive and easy to implement. The future will see more use of GIXD and depth dependent measurements, since these provide important information and can be carried out on lab-based equipment (rather than requiring synchrotron radiation). Position sensitive detectors will continue to replace counters and photographic film. 

Spectral Gamma Ray Log. This log makes use of a very efficient tool that records the individual response to the different radioactive minerals. These minerals include potassium-40 and the elements in the uranium family as well as those in the thorium family. The GR spectrum emitted by each element is made up of easily identifiable lines. As the result of the Compton effect, the counter records a continuous spectrum. The presence of potassium, uranium and thorium can be quantitatively evaluated only with the help of a computer that calculates in real time the amounts present. The counter consists of a crystal optically coupled to a photomultiplier. The radiation level is measured in several energy windows. 

A liquid scintillation counter. This instrument is used to detect radiation and measure disintegrations per minute quickly and accurately. 

A scintillation counter registers emitted radiation caused by the disintegration of nuclides. If each atom of nuclide emits one count, what is the activity of a sample that registers 3.00 X 104 disintegrations in five minutes ... 

Fluorine-18 has a decay constant of 6.31 X 10-3 min-1. How many counts will one get on a Geiger counter in one minute from 1.00 mg of fluorine-18 Assume the sensitivity of the counter is such that it intercepts 0.50% of the emitted radiation. 

Figure 2. XRD pattern of an EMD sample (Chemetals). The diffractogram is taken with a Bruker AXS D5005 diffractometer using CuKa radiation and a scintillation counter. The step width is 0.02° with a constant counting time of 10 s / step.

Fig. 5—6. Geiger-counter output currents recorded by Dow automatic x-ray absorption spectrometer. Superposed records on left are x-ray absorptiometric curves for iso-octane and a solution containing ethylene dibromide, whereas traces at right illustrate recording of transmitted intensities at fixed wavelengths. Apparent change in x-ray absorption of solvent in going through bromine absorption edge is result of marked slope of white radiation distribution curve at 0.9 A. 16 (Liebhafsky, Anal. Chem., 21, 17. Courtesy of Dow Chemical Company.)...

The second feature, the use of a secondary radiator, entails a loss of intensity because it introduces a second x-ray excitation process, but this loss is, offset to a large extent by the increased absorption of the characteristic lines from the radiator. The third feature also merits further comment. As Figure 11-7 shows, the proportional counter... 

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