## 3 Results and Analysis of Ultraviolet Photon Counting  
### Variation Characteristics of Photon Count Based on Discharge Intensity  
This study examined the corona inception process of the conductor from two aspects: ultraviolet photon counting and corona current measurement. Based on the experimental measurements, the corona current and ultraviolet photon count results of the smooth conductor at different voltages were obtained. The inflection point method was utilized to determine the corona inception voltage of the conductor [24]. By gradually applying voltage to the conductor, the discharge process went through a progression from corona inception to full corona discharge. During this process, the ultraviolet photon count and corona current increased correspondingly. The experimental procedure adopted during the experiment was as follows:  
1. Voltage was applied to the conductor and slowly increased until corona discharge was observed. The voltage was maintained at a constant level once corona discharge was established for observation and data collection purposes. After that, we started recording the ultraviolet detection data while simultaneously using the ammeter to measure the corona current. To avoid errors caused by random data, the voltage was kept constant. The average readings of the ultraviolet imager and the ammeter within 10 s were recorded as the measurement results, and then the voltage was slowly increased. The above detection process was repeated for each voltage increment. 2. Based on the controlled variable method, the gain and observation distance of the ultraviolet imaging camera were varied. The ultraviolet imaging camera was used to detect the change in the photon count around the conductor inside the corona cage. To avoid the influence of occasional data, the average value of the ultraviolet photon count measured over 10 s was taken as the measurement result. 3. After concluding the experiment, we waited for a certain period until the space charge had fully dissipated. Then, we replaced the conductor and repeated the aforementioned steps. Several typical ultraviolet images captured during the corona inception process of the 5 mm conductor are shown in Figure 3.  
In Figure 3, the red dots represent clusters of photons measured using the ultraviolet imaging camera. Each spot represents a discharge point. From the figure, it can be observed that as the voltage increased, the area of the spots gradually increased, and they spread throughout the entire length of the conductor. This reflects the process of the conductor transitioning from no corona inception to full-scale corona inception. At low voltages, the corona discharge on the surface of the conductor may not be stable. The discharge points can intermittently ignite and extinguish, resulting in an intermittent presence of photons. As the voltage increased, the corona discharge on the surface of the conductor gradually became more stable. However, it still exhibited some intermittent behavior. The photon count shows systematic variations in response to this intermittent corona discharge. At higher voltages, the intensity of corona discharge on the surface of the conductor became more pronounced. The photon count increased rapidly as the voltage rose, and the area of the spots in the discharge image also increased. With the increase in voltage, the amplitude of the current also gradually increased. To gain a better visual understanding  
Figure 3: Typical ultraviolet images of 5 mm stainless-steel conductor at different voltages: (a) 50.0 kV; (b) 51.5 kV; (c) 52.5 kV; (d) 53.5 kV. of the relationship between the photon count and the corona current, the average photon number and corona current of a 5 mm conductor are plotted in Figure 4. When plotting the correlation diagrams of ultraviolet photon counts and current in this paper, the data in the figures represent the average measurements under constant parameters. Error bars were added to the curves in the images to reflect the fluctuation of the measurement results.