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X-Ray Interactions and Energy Deposition
Published in Jerry J. Battista, Introduction to Megavoltage X-Ray Dose Computation Algorithms, 2019
Jerry J. Battista, George Hajdok
By way of analogy, this linear stopping power is akin to a vehicle’s fuel consumption rate per unit of distance travelled in metric units (e.g. litres per 100 km). The stopping power depends on the charge (i.e. type of vehicle) and speed (i.e. highway or city driving) of the particle and the nature of the stopping medium (i.e. road conditions). As the charged particle slows down, the stopping power escalates sharply because the Coulomb force exerts itself for a longer duration on passing by an atom. At a starting energy of 5 MeV, the mass stopping power for an electron in carbon (Z = 6) is 1.72 MeV per g cm−2 and the linear stopping power is 3.44 MeV per cm of travel using a density of ρ = 2 g cm−3. When the particle has slowed to a kinetic energy of 100 keV, the linear stopping power has more than doubled to 7.32 MeV per cm. The stopping power includes energy losses due to collisions with atomic electrons (i.e. collisional stopping power) and with the nucleus (i.e. radiative stopping power). The ratio of radiative to collisional stopping power can be estimated by the ratio ≈ Ek × Z/800) where Ek is the particle’s kinetic energy and Z is the atomic number of the absorber. For instance, for an electron with energy of 5 MeV interacting in carbon (Z = 6), bremsstrahlung energy losses amount to only ~ 4% of collisional losses.
Comprehensive radiological parameterizations of proton and alpha particle interactions for some selected biomolecules: theoretical computation
Published in Radiation Effects and Defects in Solids, 2023
Abayomi M. Olaosun, Denen E. Shian
Zeff is a term used to describe multi-element materials in terms of equivalent elements because the multi-element material in the continuous energy region cannot be represented by a single number (9). In medical physics, where various forms of ionizing radiation are utilized for radiological reasons such as diagnosis and therapy, Zeff is useful in computing other significant quantities such as absorbed doses. This parameter depends on energy, mass attenuation coefficient, or stopping power. Neff, on the other hand, of a multi-element material refers to the number of electrons per unit mass of the material (9) and provides definitive information regarding the scattering of the radiation through a medium (5). Zeff and Neff are beneficial in shielding and dosimetric applications since they are used to characterize various types of materials including biomolecules such as fatty acids, nucleotide bases, carbohydrates, vitamins, and lipids by correctly differentiating them in continuous energy regions based on the probability of interaction. Early diagnosis of tumors and other diseases in biological organs can be deduced with about 15–20% deviation in the normal values of Zeff and Neff of such organs (22). More significantly, such distinct separation between biological materials from one another will not only produce accurate diagnostic results but also be beneficial for the estimation of radiation dose.
Testing the suitability of FLUKA and PHITS to predict the outcome of radionuclide production
Published in Radiation Effects and Defects in Solids, 2023
M. Klink, L. Lens, J. J. W. van de Laar, U. W. Scherer
The activity of a nuclide can be calculated with the aid of the activation equation below (1). For charged-particle induced reactions with a target of a particular thickness the ‘thick target’ yield Y [2] can be calculated as Where NA is Avogadro's number, M the molar mass of the target element, H the isotopic abundance or enrichment, I the projectile current in (particles s), λ the decay constant and t the irradiation time. The term describes the stopping power and the cross section at the energy E in the lower ( E1) and upper ( E2) energy limits of the projectile in the target.
An extensive study on the neutron-gamma shielding and mass stopping power of (70-x) CRT–30K2O–xBaO glass system for 252Cf neutron source
Published in Environmental Technology, 2023
Mucize Sarihan, Roya Boodaghi Malidarre, Iskender Akkurt
One significant feature to evaluate the penetration depth of charged particles is Mass Stopping Power (MSP). The concept of the mass stopping power (MSP) refers to the reduction of the kinetic energy of the ionizing particles like proton particles (H1) and alpha particles (He+2) and can be estimated by the SRIM software in the present study. As it is seen in Figures 13 and 14, the curves for both proton and alpha undergo a sharp rise and then fall as they maximize kinetic energy. Furthermore, glass labelled as CG1 can better stop the proton and alpha particles among the rest of the candidate shielding materials.