## 2 Construction of Experimental Platform and Experimental Methods
\begin{table}
\begin{tabular}{c c c c} \hline
**TYPE** & **Sensitivity (W/cm\({}^{2}\))** & **Detection Distance (m)** & **Range of Imager Gain** \\ \hline STUV-11 & \(1.8\times 10^{-18}\) & 0.5–100 & 0–100 \\ \hline \end{tabular}
\end{table} 
Table 1: Basic parameters of the ultraviolet (UV) imager. Figure 1: Schematic diagram of experimental platform. Figure 2: Ultraviolet (UV) imagers. as Equation (2). By combining Equations (1) and (2), the corona inception voltage for the selected conductor in the mini corona cage can be determined. \[E_{on}=\frac{U_{on}}{r_{0}\ln(r_{R}/r_{0})} \tag{2}\]  
In the equation, \(E_{on}\) represents the nominal surface electric field strength on the conductor (kV/cm), \(U_{on}\) represents the voltage applied between the conductor and the corona cage (kV), \(r_{0}\) represents the radius of the conductor (cm), and \(r_{R}\) represents the radius of the corona cage (cm). For a certain diameter of the conductor, the diameter of the corona cage needs to be sufficiently small so that the conductor can exhibit the corona phenomenon at lower voltages. Additionally, there should be a sufficient air gap between the conductor and the cage walls to ensure that the breakdown voltage is at least 50% higher than the corona inception voltage. This design ensures stable observation and analysis of the corona phenomenon [22]. By combining Equations (1) and (2), it can be determined that the corona voltage range of the conductor selected in this paper was 28-51 kV under the selected corona cage size. According to the calculation based on the breakdown voltage of the easiest-to-inception positive rod-negative plate gap, the average breakdown field strength was approximately 5 kV/cm. Therefore, the breakdown voltage for a 15 cm gap was estimated as 75 kV. The calculation results indicate that the breakdown voltage was 47% higher than the corona inception voltage. Therefore, the corona cage structure used in this study essentially meets the requirements for corona inception voltage and breakdown voltage. Based on the analysis provided above, it can be concluded that the corona cage and conductor used in the experiment meet the experimental requirements. Within the applied voltage range, the corona cage allowed the conductor to initiate corona discharge effectively while providing a certain margin to observe the phenomenon without reaching the breakdown voltage. As the applied voltage on the conductor increased, the surface electric field strength of the conductor gradually exceeded the corona inception electric field, and corona discharge began. During the experimental process, before the conductor started to corona, the surface electric field of the conductor was proportional to the voltage, increasing with the increase in voltage and decreasing with the increase in the conductor radius. After the conductor started to corona, the electric field near the conductor was the composite value of the nominal electric field of the conductor and the spatial charge electric field generated by the corona discharge. However, overall, the electric field near the conductor is positively correlated with the voltage and negatively correlated with the conductor radius [23].