# Development of Compact and Robust Physical System for Strontium Optical Lattice Clock
## 4 Environmental Testing
### Mechanical and Thermal Environments  
During transportation outside the laboratory, optical clocks must endure harsh transport conditions, including the road, the sea, and even a rocket. To ensure that the system can work normally without manual adjustment after transportation, especially for mechanical structure adjustments, environmental testing is necessary to verify the adaptability of the system to various mechanical and thermal environments. Figure 8 illustrates the thermal test temperature curve of a temperature chamber calibrated by the Institute of Metrology Science. The test conditions were set according to the experimental payload requirements for the Chinese space station, encompassing the following: (1) a temperature range from +10 \({}^{\circ}\)C to +40 \({}^{\circ}\)C; (2) both high and low temperature holding times of 4 h; (3) temperature change rates averaging 3 \({}^{\circ}\)C /min to 5 \({}^{\circ}\)C /min; (4) a total of 12 cycles; (5) atmospheric pressure set to normal conditions. Tables 1 and 2 outline the test conditions for the sinusoidal swept-frequency vibration and random vibration tests, respectively. These conditions were established based on the experimental payload requirements for the Chinese space station. All equipment, including vibration tables, experimental testing equipment, and the sensors used in both test types, underwent calibration and certification by third-party metrology. The fundamental frequency of the physical system was determined through feature-level sweeping in three directions. The fundamental frequencies in the X, Y, and Z directions \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{4}{c}{**Parameter Value**} \\ \cline{2-5}
**Parameter Name** & \multicolumn{4}{c}{**Frequency Range (Hz)**} \\ \cline{2-5}
**Amplitude 0-P** & 5 mm & 2 g & 3.4 g & 2 g \\ \hline
**Load Scan Rate** & \multicolumn{4}{c}{4 oct/min} \\ \hline
**Load Direction** & \multicolumn{4}{c}{Three Axial Directions} \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Test conditions for sinusoidal swept-frequency vibration. \begin{table}
\begin{tabular}{c c c} \hline \hline  & \multicolumn{2}{c}{**Parameter Value**} \\ \cline{2-3}
**Parameter Name** & \multicolumn{2}{c}{**Frequency Range (Hz)**} \\ \cline{2-3}
**10-50** & **50-300** & **300-2000** \\ \hline
**Power spectrum density (PSD)** & 3 dB/oct & 0.0049 g\({}^{2}\)/Hz & \(-\)12 dB/oct \\ \hline
**Total Root Mean Square Acceleration (RMSA)** & \multicolumn{2}{c}{2.14 grms} \\ \hline
**Duration of Each Experiment** & \multicolumn{2}{c}{60 s} \\ \hline
**Load Direction** & \multicolumn{2}{c}{Three Axial Directions} \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Test conditions for random vibration. Figure 8: Thermal test conditions. High temperature is 40 \({}^{\circ}\)C, low temperature is 10 \({}^{\circ}\)C, each cycle is 8 h, total of 12 cycles. were measured at 49, 75, and 49 Hz, respectively, meeting the requirement that the designed fundamental frequency of the experimental payload should exceed 40 Hz. As illustrated in Figure 9 (left), the swept frequency response curve of the physical system in the Z direction at an eigenlevel of 0.2 g is presented. Figure 9 (middle, right) illustrate the sinusoidal and random response curves of the physical system, respectively. The response outcomes from both tests are deemed satisfactory. It is worth noting that, for the sake of visual clarity, Figure 9 exclusively showcases the test results along the Z-axis. After conducting the environmental tests, we proceeded with an electrical power-up test on the physical system. The vacuum of the chambers was meticulously examined and found to be identical to its pre-test state, confirming the effectiveness of the construction and support structure within the physical system. Among the system components, the lattice laser demands the strictest beam alignment, and lattice confinement denotes the final phase of cold atom capture.