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Fundamental Concepts and Quantities
Published in Shaheen A. Dewji, Nolan E. Hertel, Advanced Radiation Protection Dosimetry, 2019
Following radioactive decay, the nucleus may be left in an excited energy state—see the discussion on nuclear shell models from Section 2.2.5 and Figure 2.2. When P214o undergoes alpha decay to 210Pb (which is itself unstable), photons are emitted from the nucleus. These photons are referred to as gamma emissions since they originate in the nucleus, whereas X-rays originate in the electron orbital shells. The alpha energies and intensities for 214Po decay are listed in Table 2.7 along with the three most intense photon emissions that accompany the alpha emissions (Hubbell and Seltzer 1995). The listed decay energy was determined from the observed alpha particle energy and conservation of momentum. If the 7834 keV decay energy represents the transition to the ground state of the nucleus, then the difference between the 7034 keV and the 7834 keV decays (~800 keV) should appear as an emitted photon energy (Krane1988; Eisberg and Resnick 1985). Similarly, the difference in the next two decay energies (6736 keV and 7034 keV) is 298 keV, and this photon energy is also observed. Other photon energies represent transitions between various nuclear energy states. Since the gamma emissions are characteristic of the shell structure of the nucleus, each atom will decay with specific energies. These characteristic emission energies are routinely used to identify the radioactive nucleus via gamma spectroscopy.
Origin and Classification of Radiation
Published in Philip T. Underhill, Naturally Occurring Radioactive Material, 2018
Gamma rays are emitted with distinctive energy levels or quanta which are usually unique to the atomic transition that causes their emission (i.e., the radioactive decay of a particular radionuclide will always produce gamma rays with the same, uniquely recognizable energy). This allows identification of gamma-emitting radionuclides by a technique known as gamma spectroscopy.
Geant4 Tracks of NaI Cubic Detector Peak Efficiency, Including Coincidence Summing Correction for Rectangular Sources
Published in Nuclear Science and Engineering, 2021
Mohamed Elsafi, Jamila S. Alzahrani, Mahmoud I. Abbas, Mona M. Gouda, Abouzeid A. Thabet, Mohamed S. Badawi, Ahmed M. El-Khatib
Gamma spectroscopy is an effective technique for identifying and measuring a broad range of gamma-emitting radionuclides. Furthermore, gamma spectroscopy does not need chemical processing in many cases, and it is nondestructive. Therefore, this technique plays a very important role in measuring the activity of radioactive environmental samples; for example, gamma-ray spectroscopy techniques are used to determine the percentage of depleted uranium in environmental samples.1 The full-energy peak efficiency for a cubic detector with a rectangular cavity was evaluated by different methods using point-like radioactive sources with axial and nonaxial positions for far geometry.2,3 However, in order to acquire high detection efficiency for measuring low activity in environmental samples, the low source-to-detector distance must be performed in the measurement.
The Effect of Intrinsic Radiation from a 3 × 3-in. LaBr3(Ce) Scintillation Detector on In Situ Artificial Radiation Measurements
Published in Nuclear Technology, 2018
Li Sangang, Cheng Yi, Wang Lei, Yang Li, Liu Huan, Liao Jiawei, Zeng Liyang, Luo Yong, Wang Xiaoyu, Pei Qiuyan, Wang Jie
Since the 1950s, in situ gamma spectroscopy measurement has often been used in radiation monitoring to detect radioactive material in luggage; at border control checkpoints; for in-field monitoring; during illicit transfer of nuclear material; and in radioactive contamination sites, e.g., the Fukushima nuclear accident site.1–5 The NaI(Tl) detector is the main choice for radiation monitoring because of its high detection efficiency, stable performance, and low price. However, because of growing requirements for higher resolution in the above deployments, its performance is limited because its energy resolution is not very high.6 Cerium-doped lanthanum bromide [LaBr3(Ce)], with its excellent properties, is capable of meeting these requirements. It has high brightness (>65 000 photons/MeV), fast decay time (16 ns), and better energy resolution (<3% full-width at half-maximum at 662 keV) compared to NaI(Tl) (6% to 8%) [Fig. 1 shows the energy resolution for the 137Cs point source at 661.7 keV in the NaI(Tl) detector and the LaBr3(Ce) detector].7,8 Some researchers have already investigated the properties of LaBr3(Ce) for marine environmental monitoring6 and in vivo measurement of 131I activity retention in the thyroid,9 and because of its efficiency, others have included it for in situ gamma spectrometry and prompt gamma tests.10 However, it has been identified that lanthanum halide scintillators including the LaBr3(Ce) ones have intrinsic activity.7