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Particle Detection
Published in Walter Fox Smith, Experimental Physics, 2020
The mass attenuation coefficient depends on the energy of the gamma ray. Therefore, the graph of count rate vs. absorber thickness for radiation from isotopes that emit gamma rays strongly at multiple energies (such as 60Co) is not linear on a semilog plot; the count rate is given by R=R0,1e−μ1ρρt+R0,2e−μ2ρρt+⋯+R0,Ne−μvρρt
X-ray Vision: Diagnostic X-rays and CT Scans
Published in Suzanne Amador Kane, Boris A. Gelman, Introduction to Physics in Modern Medicine, 2020
Suzanne Amador Kane, Boris A. Gelman
The density of the material influences how many atoms the x-ray beam encounters when it passes through a given thickness of material, so denser materials are generally better absorbers of x-rays than less dense ones. This dependence makes the relatively dense bone better at absorbing x-rays than soft tissues (see Table 5.1). Because of the multiplicative dependence on density of the attenuation coefficient (see Equation 5.7), it is often convenient to use the mass coefficient of attenuation, defined as, μmass=μρ=σ×nρ=σma, where in the second step we used Equation 5.7 and the relation n = ρ/ma (ma is the mass of the atom). If the density of the material is measured in units of g/cm3, the mass attenuation coefficient is measured in cm2/g.
X-ray Computed Tomography for Diagnostic Imaging—From Single-Slice to Multi-Slice
Published in Paolo Russo, Handbook of X-ray Imaging, 2017
As demonstrated by Equations 32.1 and 32.3, the mass attenuation coefficient, μ(x, y; E), of a material is jointly dependent on its atomic number and mass density (Johns and Cunninham 1983; Bushberg et al. 2011). There exist situations in practice where two different materials are not differentiable in an MSCT image acquired at single peak voltage, as the material with the lower atomic number may possess a higher mass density. It occurs often in the diagnosis of stenosis with CT angiography that the iodine contrast in vascular lumen may not be differentiable from the calcification attached to the wall. However, the difficulty in such situations can be overcome using the dual kVP scan capability that is available in state-of-the-art MSCT scanners (see also Section III, Chapter 39, for a description of dual energy techniques in CT).
Enhanced Bentonite/PVA Matrix for Advanced Shielding Applications
Published in Nuclear Technology, 2022
Fawzy Hammad Sallam, Eman Mohamed Ibrahim, Sayed Fahmy Hassan, A. Omar
The study of gamma-ray and X-ray attenuation of different materials started in 1952 (Refs. 3 and 4), so many studies have come along with techniques of various attenuation calculations.5 Different attenuation coefficients have been investigated, such as linear and mass attenuation coefficients. The linear attenuation coefficient µ represents the probability of interaction between gamma rays and shielding material per unit path length and is considered the main factor for the penetration and diffusion of gamma rays in a shielding medium.6 Gamma-ray attenuation depends on the shielding material’s atomic number, photon energy, and density. The mass attenuation coefficient is defined as the linear attenuation coefficient per unit mass of the shielding material.7 According to Lambert’s law, linear attenuation µ can be determined as presented in Eq. (1):
The radiation shielding offered by the commercial glass installed in Bangladeshi dwellings
Published in Radiation Effects and Defects in Solids, 2018
Sabina Yasmin, Z. Siti Rozaila, Mayeen Uddin Khandaker, Bijoy Sonker Barua, Faruque-Uz-Zaman Chowdhury, Md. Abdur Rashid, David A Bradley
Given that the linear attenuation coefficient depends on the density of a material, the coefficient of mass attenuation is often used in more practical settings. In regard to utility of the latter, consider for instance the very much lower linear attenuation of water vapour than that of ice. Given that the density of molecules of water vapour is much less than that of ice, the probability of photons encountering water molecules is consequently much reduced. Normalisation of mass dividing by the density of an element or compound produces a constant value for that particular material, this constant being known as the mass attenuation coefficient. Effectively, the mass attenuation coefficient is a measure of the average number of interactions of radiation with matter taking place in a given thickness, sometimes referred to as the areal density (i.e. mass per unit area) of the target material (18). Thus, the mass attenuation coefficient (µm, typically measured in units of cm2/g) is widely used in the calculation of photon penetration and energy deposition in biological, shielding and other dosimetric materials. The attenuation of gamma rays can then be estimated from measured values of µ and ρ as follows: where ρ is the mass density (g/cm3) and t is the absorber thickness (cm).
Measurement of photon interaction parameters of high-performance polymers and their composites
Published in Radiation Effects and Defects in Solids, 2018
M. Büyükyıldız, M. A. Taşdelen, Y. Karabul, M. Çağlar, O. İçelli, E. Boydaş
In conclusion, the photon interaction properties of polymers and their composites have been examined at various photon energies using both experimental and MC based on transmission technique. The experimental results were compatible with MC and theoretical results according to mass attenuation coefficients. It was proposed that the polymer structures played important role in to the shielding properties against spatial low and high-energy radiation in the present study. Compared with a conventional passive shield, P1 and P6 exhibited better shielding capability, as indicated by lower amounts of effective electron density. The mass attenuation coefficient results have a similar tendency and display that the interaction possibility is highly relevant to the effective atomic number. The shielding properties of P1 and P6 were affected by boron and iron contents. Within these polymers, the P1 and P6 had the most boron and iron elements, respectively. Among them, the P6 sample was recommended as better armor material than the other polymers.