## 3 Measurement Tests
### Test Results and Analysis
Figure 3 gives the \(\alpha\)-particle emission spectra of the thick-film material containing \({}^{232}\)Th, which can be seen to exist in a number of peaks, which is obviously different from Figures 1 and 2. The analysis suggests that, due to the \begin{table}
\begin{tabular}{l l} \hline \hline
**Alpha Particle Emissivity Class** & **Emissivity (\(\alpha\)/(cm\({}^{2}\).h))** \\ \hline Uncontrolled Alpha & \textgreater{}0.05 \\ Low Alpha & 0.002–0.05 \\ Ultra Low Alpha (ULA) & \textless{}0.002 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Alpha particle emissivity scale. Figure 1: The \(\alpha\)-particle energy spectrum of the Sn\({}_{10\%}\)Pb\({}_{90\%}\) tin sphere emission. \begin{table}
\begin{tabular}{l l l l} \hline \hline
**Group** & **Sample Composition** & **Ball Diameter** &
\begin{tabular}{l} **\(\alpha\)-Particle Emissivity** \\ **\(\alpha\)/(cm\({}^{2}\).h)** \\ \end{tabular} \\ \hline
1\# & Sn\({}_{10\%}\)Pb\({}_{90\%}\) & 0.1 mm & 85.12 \(\pm\) 0.7 \\
2\# & Sn\({}_{63\%}\)Pb\({}_{37\%}\) & 0.1 mm & 8.47 \(\pm\) 0.2 \\
3\# & SAC305 & 0.1 mm & 3.76 \(\pm\) 0.2 \\
4\# & Low \(\alpha\) Sn\({}_{10\%}\)Pb\({}_{90\%}\) & 0.1 mm & 0.0019 \(\pm\) 0.00035 \\
5\# & Low \(\alpha\) Sn\({}_{63\%}\)Pb\({}_{37\%}\) & 0.1 mm & 0.0017 \(\pm\) 0.00029 \\
6\# & Low \(\alpha\) SAC305 & 0.1 mm & 0.0010 \(\pm\) 0.00048 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Sample alpha particle surface emissivity. fact that \({}^{232}\)Th is located in the upstream of the decay chain, its emission spectrum carries multiple-seeded nuclei and its emission spectra are different from that of Figures 1 and 2. It is surmised that, since \({}^{232}\)Th is located in the upstream of the decay chain, its emission spectrum carries the \(\alpha\)-particle energy peaks generated by the decay of multiple sub-nuclides, while the radionuclides inside the tin sphere may be located at the end of the decay chain. (3) The reason for this is that the alpha particles emitted from the inside of the tin sphere lose their energy by means of electron and nuclear energy loss during the process of ejection from the sphere, which leads to their ejection energy being lower than that of the original energy (5.3 MeV), and thus an extended region is formed. The sources of radioactivity inside the Sn\({}_{10\%}\)Pb\({}_{90}\%\) tin sphere and Sn\({}_{63\%}\)Pb\({}_{37\%}\) tin sphere were analyzed based on the energy spectra in Figures 1 and 2. The nuclides whose decay-produced \(\alpha\)-particle energies are in the interval of 5.3 MeV to 5.5 MeV, are \({}^{210}\)Po (5.304 MeV), \({}^{228}\)Th (5.423 MeV (probability of 73.4%), 5.34 MeV (probability of 26%)), and \({}^{222}\)Rn (5.489 MeV) [10]. \({}^{222}\)Rn's decay product is \({}^{218}\)Po, which has a half-life of 3.8 days, and the energy of the \(\alpha\)-particle produced by the decay is 5.489 MeV; its daughter nuclide \({}^{218}\)Po has a half-life of 3.1 s, and the energy of the \(\alpha\)-particle produced by the decay is 6.002 MeV, so there should be at least two peaks in the energy spectrum of \({}^{222}\)Rn. \({}^{228}\)Th is located in the upstream of the decay chain, and the half-lives of its decay products \({}^{224}\)Ra and \({}^{220}\)Rn are 3.7 days and 55.6 s, respectively. The energy of the \(\alpha\)-particles produced by the decay of \({}^{224}\)Ra and \({}^{220}\)Rn is 5.685 MeV and 6.288 MeV, respectively, so the energy spectrum of \({}^{228}\)Th should have at least four or more peaks. \({}^{210}\)Po undergoes \(\alpha\)-decay and produces \(\alpha\)-particles with an energy of 5.304 MeV, and \({}^{210}\)Po is the most terminal decayable nuclide, and its decay product is the stable 20\({}^{6}\)Pb, which leads to only a single peak in Figures 1 and 2. Therefore, the radionuclide within the Sn\({}_{10\%}\)Pb\({}_{90\%}\) tin sphere and Sn\({}_{63\%}\)Pb\({}_{37\%}\) tin sphere is \({}^{210}\)Po.