## 4 Experimental Results and Analysis
### Experimental Results and Analysis of Pressure Performance  
The SCRP was connected to an active supercharged supersonic diffuser, and the pressure recovery performance of the supersonic flow was analyzed using the supersonic diffuser. First, when the SCRP was not in operation, the pressure performance of the active supercharged supersonic diffuser was examined. Tests were conducted on its starting capability and its ability to maintain optical cavity pressure under various initial vacuum tank pressures and different active gas intake parameters. Figures 11 and 12 show the performance debugging test results for supersonic diffuser test piece 3#, where m\({}_{\text{D}}\) is the design flow rate of the diffuser. The diffuser's active airflow is the design flow. When the initial pressure of the vacuum tank was not higher than 4.0 P\({}_{\text{D}}\), the diffuser could start smoothly, and the pressure of the optical cavity was maintained within the range of the reaction requirements. When the initial pressure of the vacuum tank was increased to 4.33 P\({}_{\text{D}}\), although the diffuser could be started, the pressure  
Figure 10: Distribution of cavity pressure at different pumping rates with an orifice plate. \begin{table}
\begin{tabular}{c c} \hline \hline
**Pumping Rate** & **N/N\({}_{\text{D}}\)** \\ \hline
2\% & 0.637 \\
4\% & 0.631 \\
6\% & 0.642 \\
8\% & 0.635 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Energy power at different pumping rates with an orifice plate. in the optical cavity fluctuated significantly and increased gradually with time, indicating that the diffuser could no longer maintain the pressure in the optical cavity within the required reaction range. When the flow rate of the active gas was increased by 1.2 times the design flow rate, the diffuser could maintain the pressure of the optical cavity within the required range under the initial back pressure of the vacuum tank at 4.71 P\({}_{\rm D}\), and the cavity pressure exhibited a slight upward trend. If the initial back pressure of the vacuum tank continued to increase to 4.88 P\({}_{\rm D}\), it became difficult for the diffuser to maintain the pressure in the optical cavity within the required range. In the butt reaction experiment, an active booster-type supersonic diffuser was installed downstream of the optical cavity, and the outlet of the diffuser was connected to a vacuum tank. After creating a low-pressure and stable environment in the optical cavity, the chemical reaction platform was started again, and then the experiment was performed  
Figure 11: Pressure in the reaction cavity with a mass rate of active gas at the design point. Figure 12: Pressure in the reaction cavity with a mass rate of active gas of 1.2 times the design point. normally. The chemical reaction platform and the active supercharging supersonic diffuser were turned off successively after the experiment was finished. Figure 13 shows the pressure change curve of the optical cavity of test piece 1# during the docking reaction experiment using the chemical reaction platform. The active gas flow rate of the supersonic diffuser was 1.0 \(\mathrm{m_{D}}\). As can be observed from the results in the figure, the initial pressure in the vacuum tank before the experiment was approximately 4.04 \(\mathrm{P_{D}}\). At t = 2 s, the supersonic diffuser starts, and under the action of the active gas, the pressure in the optical cavity rapidly drops to approximately 0.3 \(\mathrm{P_{D}}\) and remains stable, which meets the requirements for the normal operation of the chemical reaction platform. When t = 8 s, the chemical reaction begins, reaction gas 1 enters the optical cavity, and the pressure in the optical cavity increases; however, under the action of the active gas, the pressure in the optical cavity decreases. When t = 11 s, reaction gas 2 enters the optical cavity, and the chemical reaction begins.