## 3 Results and Discussion
In this study, the TF and RPE values were mainly affected by three parameters: emitted photon E\({}_{\rm Y}\), Bi\({}_{2}\)O\({}_{3}\) doping concentration, and fabricated composite thickness. Increasing the emitted photon energy, E\({}_{\rm Y}\), caused a large increase in the penetration power of the emitted photons, which affects the values of I\({}_{\rm t}\) and I\({}_{\rm a}\). We found that a large increase in the number of I\({}_{\rm t}\) photons was accompanied by a decrease in the number of I\({}_{\rm a}\) photons. So, the TF increase is accompanied by a decrease in the RPE, leading to an increase in E\({}_{\rm Y}\) values. For example, a 1 cm thickness of the fabricated Bi\({}_{2}\)O\({}_{3}\) 10% sample had TF values that varied between 0 and 90 wt. %, whereas it had RPE values that decreased from 100 to around 9%, when the E\({}_{\rm Y}\) increased from 15 to 661 keV. The Bi\({}_{2}\)O\({}_{3}\) concentration also affects TF and RPE. Figure 6 shows the TF and RPE versus the Bi\({}_{2}\)O\({}_{3}\) doping concentration. Raising the Bi\({}_{2}\)O\({}_{3}\) content in the composites increases the composites' Z\({}_{\rm eff}\), which causes an increase in the resistance of the composite towards the passage of the emitted photons. Thus, the increase in photon-electron interactions inside the fabricated material is associated with a decrease in I\({}_{\rm t}\) photons and a significant increase in I\({}_{\rm a}\) photons. As a result, when TF decreases there is an associated increase in the RPE values. For example, at an E\({}_{\rm Y}\) of 122 keV, TF values decreased from 84.1% to 57.7% and RPE values rose from 15.9% to 42.3% as the Bi\({}_{2}\)O\({}_{3}\) concentration increased from 0 to 10 wt. %. Moreover, it has been found that the composite's thickness also affects TF and RPE, as illustrated in Figure 7. For example, at an E\({}_{\rm Y}\) of 122 keV, the TF values of the fabricated Bi\({}_{2}\)O\({}_{3}\) 10% composite decreased from 65.8% to 1.5%, whereas RPE values increased from 34.2% to 98.5% as the composite thickness increased from 0.5 to 5 cm. Raising the fabricated composite thickness from 0.5 to 5 cm caused an bigger increase in the path length of the photons than the relaxation length of photons. Thus, the emitted photon performs more collisions inside the fabricated composite before penetrating the composite bulk. As a result, there is an increase in I\({}_{\rm a}\) and a significant decrease in the number of I\({}_{\rm t}\) photons. Therefore, the decrease in TF is associated with an increase in RPE values. Figure 5: Influence of Bi\({}_{2}\)O\({}_{3}\) concentration on \(\Delta_{0.5}\) and relaxation length (\(\lambda\), cm). The \(Z_{\rm eff}\) is the parameter used to examine the attenuation properties of a multi-element composite in terms of its equivalent element. Figure 8 depicts the \(Z_{\rm eff}\) for the current samples versus the \(\gamma\)-photon energy. For example, at an E\({}_{\gamma}\) of 15 keV, the fabricated composites, Bi\({}_{2}\)O\({}_{3}\) 0%, Bi\({}_{2}\)O\({}_{3}\) 5%, and Bi\({}_{2}\)O\({}_{3}\) 10%, have shielding parameters similar to Na (Z = 11), Cr (Z = 24), and Se (Z = 34), respectively. These values for \(Z_{\rm eff}\) decrease when the emitted gamma photon energy increases. For example, at E\({}_{\gamma}\) values between 15 keV and 661 keV, the fabricated composites, Bi\({}_{2}\)O\({}_{3}\) 0%, Bi\({}_{2}\)O\({}_{3}\) 5%, and Bi\({}_{2}\)O\({}_{3}\) 10%, act as Be (Z = 4), B (Z = 5), and C (Z = 6), respectively. Figure 8 shows two peaks where the \(Z_{\rm eff}\)  
Figure 6: Dependence of transmission factor (TF, %) and RPE on the Bi\({}_{2}\)O\({}_{3}\) concentrations at a \(\gamma\)-photon energy of 122 keV. Figure 7: Dependence of TF and RPE on the composite thickness for composites Bi 0% and Bi 10%. has an unexpected increase. This increase in the \(Z_{\text{eff}}\) values is attributed to the L1 and K absorption edges of Bi that appear at 16.3 keV and 90.5 keV, respectively.