## 2 Experiments  
### Test Specimens  
The amorphous soft magnetic sheets were manufactured by the melt-spinning method, and they were 20-25 \(\upmu\)m thick and 210 mm wide. It was necessary to measure the electromagnetic wave shielding effectiveness (SE) of the base material sheet first, since this was cut into thin pieces to obtain soft magnetic fibers. The point-of-entry (POE) shape of electromagnetic waves was artificially diversified through various combinations and structural arrangements of amorphous soft magnetic sheets and conductive sheets. The shielding effectiveness (SE) was measured in a range from 1 kHz to 10 GHz according to the criteria of MIL-STD-188-125-1 and MIL-DTL-83528D. Protection frequency range against nuclear EMP threat had been required for up to 1 GHz, but it was recently extended to 10 GHz against non-nuclear EMP threat. In this study, the shielding region was evaluated for up to the maximum 10 GHz to protect against both nuclear and non-nuclear EMP threat.  
Electromagnetic waves can be passed through the space (holes) between the fabrics depending on the frequency if the fabric is made of amorphous soft magnetic fibers. It was assumed that the shielding efficiency would be improved if the holes were blocked by a flexible conductive material. In other words, we expected to satisfy the shielding performance with a composite material composed of an amorphous soft magnetic material and a conductive material.  
The experiment was conducted under the following conditions:  
First, a long slit-shaped defect was intentionally formed between the amorphous soft magnetic sheets without the addition of the conductive material layer. Then, a vertical wave and a horizontal wave were irradiated to the slits according to the criteria of MIL-STD-188-125-1 and MIL-DTL-83528D. As a result of the SE test, no significant values were obtained without a conductive layer.  
Second, several amorphous soft magnetic sheets with various slit conditions were prepared to analyze the influence of the conductive layer on SE. Adhesive conductive tape was added to the soft magnetic sheet to produce composite materials, as shown in Figure 1. The effect of the conductive tape on the results was negligible. To increase the accuracy of SE measurement, the size of the specimen was manufactured to be 1000 mm in width and length.  
Third, the best composite material satisfying the SE of 80 dB was selected for fibers in the next steps. In this paper, only the preceding research necessary for the optimal fiber composite material candidate was conducted.  
A specimen of a multilayer structure was manufactured by adding conductive tapes of various widths or varying the overlapping method of the slits of a soft magnetic sheet, as shown in Table 3.  
Figure 1: Top and side views of the amorphous soft magnetic composite specimen.  
As shown in Figure 2, conductive tape lengths with widths of 0, 20, 50 and 100 mm were attached to the slits of the amorphous soft magnetic sheet, in specimens #1 to #4, respectively. In specimens #5 and #6, conductive tape with widths of 50 and 100 mm was attached to the slit of the amorphous soft magnetic sheet, and an additional conductive tape with a width of 20 mm was overlapped. In specimen #7, conductive tape was superimposed between amorphous soft magnetic sheets in a sandwich structure. In specimen #8, conductive tape was stacked between amorphous soft magnetic sheets in a sandwiched structure at an angle of 90 degrees.  
Figure 2: Shape of the specimen.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & & & & & **Specimen No.** & & & \\ \cline{2-8}  & **1** & **2** & **3** & **4** & **5** & **6** & **7** & **8** \\ \hline Width of & & & & & & & & \\ conductive & 0 mm & 20 mm & 50 mm & 100 mm & 50 mm + 20 mm & 100 mm + 20 mm & 1000 mm & 1000 mm \\ layer(W) & & & & & & & & \\ \hline Arrangement of & & & & & & & & \\ magnetic layers & & & & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 3: Types of specimens.