Gamma Ray Attenuation Using Nanocomposites for Multiple Radioactive Sources

INTRODUCTION
Finally, in order to enhance the accuracy of atomic and/or mass attenuation coefficient, a series of measurements were presented. The value of mass attenuation coefficient is not only important for the medical imaging systems, but also for the design of shielding materials against radiation [1]. Even though there are intriguing anecdotal evidence in this direction, in practice theory and experiment often have little to do with one another especially for novel or complex materials [2]. Such variations could lead to insufficient attenuation, or errors in image donation and highlight the need for regular validation of these data [3,4]. The gamma ray attenuation effect from sources such as Am-241, Cs-137, and Co-60 by this material of different densities had been reported previously in some other investigations [5, 6]. The main purpose of irradiating source samples [7] is to find the density (m) and m/ for each sample source. The low-density materials are proven to be effective in shielding the low ɣ emitters [8]. For high energy sources such as Co-60, it is required to use High Z or thick material with high mass density materials for efficient radiation shielding [9]. The mode should be extended to character formation in media with complex geometries, composites of materials58 different [10] for better prediction accuracy of the attenuation coefficients. This work could be a contribution in the literature as an investigation of scintillation properties of the material for gamma-ray absorption application. These results can be of interest in all the fields such as nuclear medicine, material science and radiotherapy [11]. The results may serve as a useful data for the researchers in the field of radiation shielding, dosimeter, and simulation based on radiation physics. Efferent substances are essential in fields such as nuclear medicine, radiological safety, and industrial radiography. Owing to their high penetration capabilities, gamma rays interact through mechanisms such as the photoelectric effect, Compton scattering, and pair production.
Research Objectives: 
1. To define and explain the mass attenuation coefficient in relation to gamma ray interactions with matter.
2. To review and analyze relevant experimental and theoretical studies involving various materials and their attenuation characteristics.

MATERIALS AND METHODS
Epoxy resin composites reinforced with 35 nm cobalt ferrite nanopowder were prepared by adding 1%–4% of cobalt ferrite powder to epoxy resin. Mechanical mixing and ultrasonic technology were applied to distribute the powder within the resin before adding the hardener. The mixture was poured into standard sample molds of 20 mm diameter and 15 mm thickness. A Geiger counter was used to calculate the linear absorption coefficient and mass absorption for all radioactive sources and the same sample. This device detects ionizing radiation, including gamma rays. Its working principle is based on the ionization of the gas inside the tube when exposed to radiation, resulting in an electrical pulse that can be detected and recorded. For the analysis of gamma ray attenuation, the device measures the radiation intensity before and after the radiation passes through a material. The attenuation rate μ is then calculated using appropriate equations [12]:

μ = (1 / x) * ln(I₀ / I)
 
where: μ = linear attenuation coefficient, x = sample thickness, I₀ = original intensity, I = measured radiation intensity after passing through the material.

RESULTS AND DISCUSSION
SEM analysis
The image in Fig. 1 shows a scanning electron microscope examination of cobalt ferrite powder. The Fig. 1 shows the presence of clusters and aggregates, the reason for which is due to the method of preparation. The figure also shows the overlap and regular distribution between the ferrite and cobalt, which gives the polymer magnetic properties and increases the magnetic susceptibility.
This study investigates the interaction between the gamma rays emitted by different radioactive sources (Am-241, Cs-137, and Co-60) and a shielding material of varying densities (Tables 1-3 and Fig. 1). The goal is to evaluate the linear attenuation coefficient (μ) and mass attenuation coefficient (μ/ρ) for each source and sample.

Linear Attenuation Coefficient (μ), Calculated as μ = 1/ x ln I0 / I
Am-241 (59.6 keV) is associated with the highest linear attenuation coefficient across all the samples. This is expected, as low-energy photons are likely to be absorbed or scattered by matter, leading to a high attenuation. Cs-137 (661.6 keV) is associated with moderate linear attenuation values. As the photon energy increases, the probability of interaction (especially photoelectric effect) decreases, thereby reducing the linear attenuation. Co-60 (1173 and 1332 keV) is associated with the lowest μ values. This finding is consistent with high-energy gamma rays having a low likelihood of interaction per unit distance in matter.

Mass Attenuation Coefficient (μ/ρ), Where ϼ = density

The mass attenuation coefficient normalizes linear attenuation to the material’s density for a comparison across different sample densities. While μ decreases with the increasing energy, μ/ρ emphasizes the difference in material effectiveness regardless of density [13]. μ/ρ shows a decreasing trend in the order of Am-241>Cs-137>Co-60, confirming the inverse relationship between photon energy and attenuation efficiency. This trend aligns with the following well-established photon–matter interaction principles:
1- At low energies, the photoelectric effect dominates. This effect has a strong dependence on atomic number (Z) and results in high attenuation (as observed for Am-241).
2- At intermediate energies, Compton scattering is the primary mode of interaction, contributing moderately to attenuation (e.g., Cs-137).
3- At high energies, pair production becomes possible (above 1.022 MeV) but contributes less than the photoelectric effect and Compton scattering unless the material is extremely dense or thick, explaining the low μ for Co-60.
These findings confirm that for effective gamma shielding:
1- Low-energy gamma-ray sources require less dense material for significant attenuation.
2- High-energy gamma-ray sources such as Co-60 require materials with high Z and/or great thickness.
Table 3 shows the linear attenuation coefficient (u) and mass attenuation coefficient (u/rho) for each radioactive source and sample (S0–S4) based on experimental data. Sample S0 is considered the baseline sample with initial intensity measurements presented in [14]. Table 1 presents the linear (u) and mass attenuation coefficients (u/ρ) of five different samples (S0 to S4) with increasing density exposed to gamma radiation from four radioactive sources: Am-241, Cs-137, and Co-60 (1173 and 1332 keV).

Effect of Energy on Attenuation
An inverse relationship exists between photon energy and both attenuation coefficients. Am-241 (59.6 keV) consistently shows the highest u and u/ρ values across all the samples. As energy increases (Cs-137 at 661 keV and Co-60 at 1173 and 1332 keV), both coefficients decrease [15]. This finding is in line with the theory of gamma interaction with matter: The photoelectric effect is strongly dependent on atomic number (Z) dominates at low energies, leading to significant attenuation. At intermediate energies, Compton scattering becomes dominant, causing moderate attenuation. At high energies (>1 MeV), pair production becomes significant, though only in very dense materials.

Effect of Material Density (Sample Variation)
As the sample density increases from S0 (1.24 g/cm³) to S4 (2.60 g/cm³), the following patterns are observed: The mass attenuation coefficient (u/ρ) tends to decrease, indicating that increasing density alone is not always efficient for shielding enhancement (Fig. 2). The linear attenuation coefficient (u) slightly decreases or plateaus, especially for high-energy gamma-ray sources, due to the diminishing effect of added thickness on highly penetrating radiation [16].

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CONCLUSION
The linear (u) and mass (u/ρ) attenuation coefficients of samples S0–S4 in the presence of gamma-ray sources Am-241, Cs-137, and Co-60 were analyzed. The following conclusions were drawn: 
1- Low-energy gamma-ray sources (e.g., Am-241 at 59.6 keV) exhibit significantly higher attenuation coefficients than high-energy gamma-ray sources.
2- Photon energy is inversely related to linear and mass attenuation coefficients.
3- The mass attenuation coefficient (u/ρ) decreases with the increasing material density, indicating diminishing returns in shielding beyond certain density thresholds.
4- The linear attenuation coefficient (u) shows a plateau trend at high densities, especially for high-energy gamma-ray sources such as Co-60.
5- As a baseline, sample S0 provides a reference point for assessing the impact of increasing density in subsequent samples.
6- Effective gamma shielding design must consider photon energy and material properties (such as density and thickness).
7- The results align with expected radiation–matter interaction models: photoelectric effect, Compton scattering, and pair production.
8- For low-energy gamma-ray sources, increasing density significantly improves shielding. For high-energy radiation, material selection and total thickness are more crucial than density.

CONFLICT OF INTEREST
The authors declare that there is no conflict of interests regarding the publication of this manuscript.