## 4 Conclusions  
The temperature calibration test was designed for the main charge of HMX-based booster in this paper. Based on the temperature calibration results, small scale gap tests were conducted on HMX-based booster at low and elevated temperatures, and the corresponding critical gap thickness G\({}_{50}\) was obtained. A numerical simulation of the shock initiation process of SSGT for HMX-based booster at different temperatures was conducted to predict the critical gap thickness G\({}_{50}\) and critical initiation pressure. The effects of different temperatures on the shock sensitivity of HMX-based booster were analyzed. The following conclusions are drawn:  
Under the same assembly conditions, the low and elevated temperature calibration experiments were conducted separately. The temperature change equation inside the steel sleeve was established for HMX-based booster charge. The temperature change trend of HMX-based booster under low-temperature conditions showed an exponential increase, while under high-temperature conditions, it showed an exponential decrease. The temperature calibration test results of the booster charge provide an experimental basis for temperature changes in SSGT. According to the results of the temperature calibration experiments, small scale gap tests were conducted on HMX-based boosters at \(-\)25 \({}^{\circ}\)C, 25 \({}^{\circ}\)C, 88 \({}^{\circ}\)C and 120 \({}^{\circ}\)C. The critical gap thickness prediction formula with temperature as the independent variable was constructed. The critical gap thickness G\({}_{50}\) of HMX-based booster under corresponding temperature conditions was obtained to be 6.3-6.4 mm, 7.2-7.3 mm, 7.5-7.8 mm and 8.3-8.4 mm, respectively. From the experimental results of SSGT, it can be observed that the critical gap thickness G\({}_{50}\) of HMX-based booster increases gradually with the rise of the initial heating temperature. And the gap prediction formula for the shock sensitivity of HMX-based booster explosive was established. Based on SSGT test data under different temperature conditions, the pressure variation processes with different gap thicknesses were simulated for HMX-based booster. The simulated prediction results of SSGT show that the critical initiation pressure of HMX-based booster is 4.6 GPa (\(-\)25 \({}^{\circ}\)C), 3.6 GPa (25 \({}^{\circ}\)C), 2.7 GPa (88 \({}^{\circ}\)C) and 2.2 GPa (120 \({}^{\circ}\)C), respectively. On the basis of the simulation test data, a prediction formula of the critical initiation pressure with temperature as the independent variable was constructed. The critical initiation pressure decreases gradually with the increase in temperature and shows exponential decay. This indicates that temperature has a significant effect on the shock sensitivity of HMX-based booster. The shock sensitivity of HMX-based booster explosive charge in the low and elevated temperature conditions has undergone significant changes and its mechanism have been analyzed. The main mechanism by which temperature affects shock sensitivity of HMX-based booster explosive is that the microstructure and mechanical properties of the booster charge undergo corresponding changes when the external temperature changes. These situations result in the shock initiation of booster charge not easily generating hotspots at low temperatures, but relatively easily forming hotspots at high temperatures. Therefore, HMX-based booster explosive at low temperature and elevated temperature become sensitive to insensitive. The research results provide a theoretical basis for the design of booster explosive formula, as well as the reliability and safety of shock initiation. Conceptualization, J.Y. ([PERSON]); Methodology, J.Y. ([PERSON]); Validation, X.T. and J.Y. ([PERSON]); Formal analysis, N.W. and Q.Y. ; Data curation, P.H. ; Writing--original draft, J.L. and X.T. ; Writing--review & editing, J.Y. ([PERSON]) and J.L. ; Visualization, P.H., Q.Y. and J.Y. ([PERSON]). All authors have read and agreed to the published version of the manuscript.