## 2 Materials and Methods
This method is based on the plain weave method, but since the ratio between the weft and warp threads is changed, weaving at high density is possible. When the fiber fabric is compressed to form a laminated structure, improved shielding performance can be expected, but flexibility of the shielding fiber cannot be expected. The intensity of radiation energy attenuates as it passes through the shielding fiber. As a result, the shielding fiber absorbs energy, and therefore, the X-ray linear attenuation coefficient is required to calculate the absorbed energy. The linear attenuation coefficient is a value indicating the extent to which the radiation is attenuated; it is in units of cm\({}^{-1}\). The equation for obtaining the linear attenuation coefficient, \(\mu\), is as follows:  
\[\mu=\frac{In\left(\frac{b_{0}}{T}\right)}{t} \tag{1}\]  
Figure 3: Process for fabrication of shielding fiber (rapier loom, Dornier, HTVS 8/S20). Figure 2: Process for fabrication of yarn for shielding fiber. where \(I_{0}\) is the dose incident on the shield, \(I\) is the dose transmitted through the shield, and \(t\) is the shield thickness (cm). The shielding performance of radiation shields, used in medical applications, is often indicated in terms of lead equivalency (mmPb). The lead equivalent is the thickness of Pb that would provide the same shielding effect as the shield when it is irradiated with radiation. The shielding performance of a shielding fiber differs significantly from that of Pb; therefore, it is difficult to express it in lead equivalence. Consequently, in this study, the same thickness is suggested based on the standard aluminum equivalence [27]. Al is mainly used for filtering high energy X-rays in X-ray generators. This study, after measuring the shielding performance while changing the thickness of the Al filter from 0.1 mm to 4 mm, proposed a formula for calculating the aluminum equivalent, \(D_{\mathrm{Al}}\) (mmAl):  
\[D_{\mathrm{Al}}=\frac{\mu_{\mathrm{F}}}{\mu_{\mathrm{Al}}}\times D_{\mathrm{F}}, \tag{2}\]  
where \(\mu_{\mathrm{Al}}\) represents the linear attenuation coefficient of Al, \(\mu_{\mathrm{F}}\) represents the linear attenuation coefficient of the shielding fiber, and \(D_{\mathrm{F}}\) represents the thickness of the shielding fiber. Thus, in this experiment, the shielding performance of the fabricated shielding fiber was evaluated based on Equations (1) and (2). In order to change the radiation used in this experiment into effective energy, which is a single energy, \(\log_{e}\) is taken on both sides in the attenuation exponential law(\(I=I_{0}e^{-\mu X}\), where \(\chi\) is the attenuation thickness), and the slope is calculated from the graph of \(\mu=-\alpha\chi\) to measured the half-value layer. In addition, after obtaining the value of the linear absorption coefficient \(\mu\) from this slope, it could be calculated as the half-value layer = 0.693/\(\mu\). Finally, effective energy was calculated using [PERSON]'s mass absorption coefficient table [28] in order to calculate the effective energy having the same half-value layer as the single energy corresponding to the single energy from the previously obtained half-value layer. The experimental method for testing the shielding performance of the two types of shielding fiber was the geometric condition shown in Figure 4, and the shielding rate of the shielding fibers was calculated as \((1-W/W_{0})\times 100\)[29], where \(W\) is the dose measured when there is shielding fiber between the X-ray tube and the dosimeter, and \(W_{0}\) is the dose measured when there is no shielding fiber between the X-ray tube and the dosimeter. All values were tested 10 times using an X-ray generator (Toshiba E7239, 150 kV-500 mA, Tokyo, Japan), and the average value was used. The dose detector was a DOSIMAX _plus_ I (IBA Dosimetry), which was used after inspection and calibration. Figure 4: Experimental setup for evaluating the performance of the shielding fiber.