## 3 Results and Discussion
### Experimental Results at Non-Ambient Temperature  
The assembled acceptor charge was put into the freezer for at least 5 h under the seven gears mode of quick freezing, and then, it was taken out and placed outdoors to monitor the temperature change. According to the data recorded by the temperature sensor, the change temperature curves of the current outdoor and HMX-based booster inside the steel sleeve were drawn by Origin software, and the temperature fitting curve of HMX-based booster inside the steel sleeve was fitted, as shown in Figure 6.  
The law equation of the temperature change in HMX-based booster inside the steel sleeve was obtained:  
\[\mathrm{T}=10.68-37.52e^{-0.068t} \tag{4}\]  
where \(T\) is the ambient temperature, \({}^{\circ}\)C; and \(t\) is the measurement time, min. The coefficient of correlation is R\({}^{2}\) = 0.9988, indicating that the measured temperature curve is in good agreement with the fitting curve. Due to the closed wrapping of aluminum foil paper over the steel sleeve, the temperature of HMX-based booster is not affected by outdoor temperature, so its temperature changing curve shows more regularity. Because the outdoor temperature is higher than the inner temperature of the steel sleeve, the change trend of HMX-based booster temperature increases exponentially. The same cooling method was used to carry out SSGT of HMX-based booster. The outdoor temperature measured by the thermometer during the test was within the range of Equation (4). The time from taking out the acceptor charge from the refrigerator to ignition was controlled at 42-46 s. Equation (4) was used to calculate that the temperature \begin{table}
\begin{tabular}{c c} \hline \hline
**Exp/num** & **Depth of Dent/mm** \\ \hline
1 & 1.90 \\
2 & 1.74 \\
3 & 1.81 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: SSGT results with no gap at 25 \({}^{\circ}\)C.  
Figure 6: Temperature calibration curve of HMX-based booster at \(-\)25 \({}^{\circ}\)C.  
of the acceptor charge when initiating the donor was \(-25.1\)\(-\)\(-\)\(-24.9\)\({}^{\circ}\)C, approximately \(-25\)\({}^{\circ}\)C. A total of five tests were carried out, and Table 4 lists SSGT experimental results at \(-25\)\({}^{\circ}\)C. The critical thickness was found to be between 6.3 and 6.4 mm based on the experimental data. [PERSON] et al. [35] conducted SSGT of HMX-based accelerants at 88 \({}^{\circ}\)C. A total of six tests were conducted, and the obtained critical gap thickness of PMMA based on HMX-based booster detonation was approximately between 7.5 and 7.8 mm. Table 5 lists SSGT experimental results at 88 \({}^{\circ}\)C.  
The acceptor charge was put into the oil bath oven and heated at 130 \({}^{\circ}\)C for 4 h. The temperature fitting curve of HMX-based booster inside steel sleeve is shown in Figure 7.  
The law equation of the temperature change of HMX-based booster inside the steel sleeve was obtained:  
\[T=33.27+91.12e^{-0.061t}\] \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Exp/num**} & \multicolumn{2}{c}{**PMMA Gap**} & \multirow{2}{*}{**Depth of Dent/mm**} & \multirow{2}{*}{**Go/No Go**} \\  & **Thickness/mm** & & \\ \hline
1 & 6.8 & 0.22 & No go \\
2 & 5.9 & 1.46 & Go \\
3 & 6.5 & 0.44 & No go \\
4 & 6.3 & 1.68 & Go \\
5 & 6.4 & 0.34 & No go \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Experimental results of SSGT at \(-25\)\({}^{\circ}\)C. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Exp/num**} & \multicolumn{2}{c}{**PMMA Gap**} & \multirow{2}{*}{**Depth of Dent/mm**} & \multirow{2}{*}{**Go/No Go**} \\  & **Thickness/mm** & & \\ \hline
1 & 9.4 & 0.02 & No go \\
2 & 9.1 & 0.04 & No go \\
3 & 8.4 & 0.44 & No go \\
4 & 8.0 & 0.20 & No go \\
5 & 7.5 & 1.76 & Go \\
6 & 7.8 & 0.36 & No go \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Experimental results of SSGT at 88 \({}^{\circ}\)C.  
Figure 7: Temperature calibration curve of HMX–based booster at 130 \({}^{\circ}\)C.  
where \(T\) is the ambient temperature, \({}^{\circ}\)C; and \(t\) is the measurement time, min.