Infrared data from the Spitzer space telescope are shown in red; and radio data from the Very Large Array are displayed in orange. Gamma Rays. Retrieved [insert date - e. Science Mission Directorate. National Aeronautics and Space Administration.
Brighter colors in the Cygus region indicate greater numbers of gamma rays detected by the Fermi gamma-ray space telescope. Krause et al. Electromagnetic Spectrum Series Series Homepage. Infrared Waves. Reflected Near-Infrared. Visible Light. Ultraviolet Waves. Earth's Radiation Budget. Diagram of the Electromagnetic Spectrum. Recommended Articles. September 24, The linear attenuation coefficient is inversely proportional to a quantity called a half-value layer HVL , which is the material thickness needed to attenuate the intensity of the incident photon beam to half of its original value.
From Eq. The HVL of a given material thus characterizes the quality penetrance or hardness of a gamma beam. Figure 2 shows the relationship between the linear attenuation coefficient and the HVL for a soft tissue [ 3 ]. Relationship between the linear attenuation coefficient and the HVL for a soft tissue.
Apart from the use of nuclear energy for the supply of electricity, the applications of radioactivity are numerous in many areas: medical physics, earth sciences, industry and preservation of cultural heritage. The properties used for these various applications are: Time decline of radioactivity. A few months after the discovery of X-rays, there is over a century, it has become clear that biological action radiation could be used in the treatment of cancers.
Cancers cells divided more quickly are more sensitive, than normal cells to ionizing radiation. By sending these cells a certain dose of radiation, it is possible to kill them and eliminate the tumor. Irradiation of surgical and food material: Irradiation is a privileged means to destroy micro-organisms fungi, bacteria, virus…. As a result, many applications radiation exists for sterilization of objects. For example, most medical-surgical equipment disposable syringes, etc.
Similarly, the treatment by irradiation of food ingredients allows improve food hygiene: sterilization spices, elimination of salmonella from shrimp and frog legs.
This technics is also known as food ionization. Irradiation of art objects: Treatment with gamma rays helps to eliminate larvae, insects or bacteria lived inside objects, to protect them from degradation. This technics is used in the treatment of conservation and restoration of arts objects, ethnology and archaeology. It is applicable to different types of materials: wood, stone, leather, etc.
Elaboration of materials: Irradiation causes, under certain conditions, chemical reactions that allow the development of more resistant materials, more lightweight, capable of superior performance. This measurement technics exploits a fundamental property observed for unstable nuclei: the emission of radiation from the process of nuclear decay. It is thus known as non-destructive because it respects the integrity of the object to be analyzed [ 4 ].
This development was made possible by a better understanding of the process of photon interaction with matter, and especially by the appearance of semiconductor detectors in the s.
It is now used in a wide variety of sectors for example: dating, climatology, astrophysics, medicine and in virtually all stages of the fuel cycle. Photon spectrometry is a commonly used nuclear measurement technique to identify and quantify gamma emitting radionuclides in a sample. It is non-destructive and does not require specific sample preparation. Conventional spectrometers are designed around semiconductor detectors, usually with high purity germanium hyper-pure germanium.
The radionuclides measured by this method emit gamma photons of specific energies and their interactions with the detector depend on several variables geometry or conditioning: physical shape of the object, density, measured quantity, container type, emission energy, size, shape, nature of the detector, etc.
The thermoluminescence dating method TL requires a very accurate knowledge of the annual radiation doses deposited, in the minerals that are used, by the alpha, beta, gamma and cosmic rays [ 5 , 6 ].
Gamma-ray dose-rate may be measured by a TL dosimeter. But as this dose is not valid for the dosimeter itself, corrections must be made to know the one corresponding to the soil. These corrections are related to the complexity of the energy spectrum gamma radiation incidents; their origins are: The difference in composition between TL dosimeter and the soil, resulting in absorption and therefore deposited different doses, especially for an energies less than keV.
The correction factors had already been investigated theoretically [ 7 ] and experimentally [ 8 , 9 ]. Below, we describe a theoretical evaluation method, for these factors, which does not require excessive computer time and so can be easily extended to a wide variety of site conditions. The calculations presented here refer to CaSO 4 : Dy as dosimeter, and two encapsulating materials, polyethylene and copper, of various thicknesses Figure 3.
However, the resulting computer programs can be easily extended to other materials. Several kinds of soils were considered. The relative energies and intensities of the lines taken into consideration are given in Table 1 [ 10 ]. For the uranium series, the contribution of uranium and its descendants were taken into account. The bulk of the calculation therefore comes down to a few dozen successive numerical integrations, with about steps each time.
It is therefore a much lighter and less demanding procedure in computer time than the Monte-Carlo method for a similar definition. In fact, formula Eq. For the use of these formulas, it is assumed that there is an electronic equilibrium, that is, the dimensions of the dosimeter are equal to or greater than the secondary electron range of the order of a few mm. Murray [ 9 ] showed that this is verified if the dosimeter mass is greater than mg. In applying formula Eq. Here one assumes an infinite environment and homogeneous, in which the radioelements are evenly distributed.
Let N 0 E be the primary spectrum number of photons per unit time and unit mass of soil. Figure 4 an example of various order spectra for 40 K. The value of absorption or attenuation coefficients was obtained for the Compton effect from the Klein-Nishina formula. For the photoelectric effect, they were deduced from the data of Hubbell [ 12 ]. Some typical spectra are shown in Figure 5 for 40 K. The low energy cut-off is determined by photoelectric effect and occurs at higher energy for high-Z media.
And for Th in pure water Figure 6. Computed energy spectra for 40 K in a dry C soil, b wet S soil, and c pure water [ 5 ]. Computed energy spectra for Th in pure water [ 5 ]. Similar features are also noticed for the more complex case of U and Th series. There is a similarity in the degraded spectrum, even for two very different gamma sources for example, thorium and potassim By printing microscopic, invisible amounts of radioisotopes onto an item, the unique digital fingerprint can be read and verified with gamma-ray spectroscopy.
Gamma rays are produced by the hottest and most energetic objects in the universe, like neutron stars, supernova explosions, and areas around black holes. Gamma-ray astronomy presents unique opportunities to explore the universe, search for new physics, test theories, and perform experiments that are not possible in Earth-bound laboratories.
Research at NNSA spans the entire electromagnetic spectrum.
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