## 2 Materials and Methods  
During radiation shielding, energy is dissipated through interaction with the elements in the medium as the radiation passes through, with an intensity that is directly proportional to the thickness of the shielding material [27]. The degree of dissipation of the radiation energy is called the linear attenuation coefficient of the medium [28]. We assume that the initial intensity of the radiation is \(I_{0}\), and the linear attenuation coefficient is \(\mu\). When direct radiation passes through the medium, the passed intensity (\(I\)) when penetrating through its thickness, \(t\), is expressed in Equation (1) [29] as follows:  
\[I=I_{0}e^{-\mu t} \tag{1}\]  
where \(\mu\) varies with the energy intensity of the radiation, and \(t\) is expressed as the thickness of the material through which the radiation, such as the mass or number of atoms per unit area, passes. As a result, the shielding performance of the plate can be determined using the thickness of the shield and the linear attenuation coefficient. Therefore, during manufacturing, a method to increase the density is frequently utilized to increase the mass per unit area. When a shield is manufactured by applying the rolling method to tungsten, which is commonly used as an eco-friendly shielding material, the density can be fundamentally higher than that obtained when using the conventional method of mixing tungsten powder with a polymer resin. However, a suitable processing technology that reduces thickness and increases processability is required for the manufacturing process. Firstly, to compare and evaluate the shielding performance of the tungsten plate, changes in the shielding performance based on the processing technology and thickness were analyzed. The average particle size of the tungsten powder for the plate used in this experiment was 4.28 + 0.1 \(\upmu\)m, and the purity was over 99%. Using a 1 mm plate (Beijing Tianlong tungsten Technology Co. Ltd., Beijing, China), 0.3 mm and 0.1 mm plates were manufactured via hot rolling, and 0.1 mm plates were manufactured via cold rolling. The composition of the manufactured tungsten plate was analyzed via energy-dispersive X-ray spectroscopy (EDS, Hitachi, HD-2300, Japan). Hot rolling was performed at 1550 \({}^{\circ}\)C, which is 0.22 times the melting point of tungsten, and the roll speed for both the upper and lower rolls was 80 mm/s. Cold rolling was performed at a relatively low temperature of 850 \({}^{\circ}\)C. In addition, the cumulative reduction during the hot-rolling process was adjusted based on the 0.3 mm and 0.1 mm thicknesses, and the thickness was adjusted via forging. The rolling process can increase the density while removing internal porosity through the application of pressure to the solid-state material [30]. Moreover, the mechanical strength can be increased by constructing a dense particle structure. Although cold and hot rolling entail similar manufacturing processes, the heat treatment process applied to the tungsten plate differs with temperature. The tungsten plate manufactured via hot and cold rolling was observed using an optical microscope (FESEM; field-emission scanning electron microscope, Hitachi, S-4800). The density of the internal structure was visually compared and analyzed by observing the surface and cross-section at the same magnification. In addition, to evaluate the shielding performance of the tungsten plate, a diagnostic X-ray generator (Toshiba E7239, 150 kV-500 mA, 1999, Tokyo, Japan) was used. As is the case in medical radiation, the tube current was fixed at 200 mA, and the experiment was conducted at tube voltages of 40 kVp, 60 kVp, 80 kVp, 100 kVp, and 120 kVp, consistent with the range used in human radiography. A radiation dose detector, Mo.9517 Radiation Monitor (Radcal Corporation, Monrovia, CA, USA), and an Mo10\(\times\)5-6, 6 cc ion chamber (Radcal Corp.) were used. Both radiation detectors were inspected and calibrated before use.