# An Investigation into the Behavior of Cathode and Anode Spots in a Welding Discharge
## 3 Results
### The Spark Stage
Figure 7 illustrates the outcome of the photography process. The anode is located at the bottom of the frame, and the upper part of the frame is the cathode. The cathode surface is inaccessible for photographing, and we see part of its image, 5 A, in the frame. In the image, the cathode spots are clearly visible. We take a direct photo of the anode's surface. We draw a thin line on the anode's surface in the photo for ease of viewing. Experiments have shown that near the anode, one can observe fairly clear contours of the anode glow (Figure 4a), which allows one to determine its location. Thus, in principle, it is possible to simultaneously determine the position of the arc bindings on both electrodes using such photographs. However, a thorough examination of the photographs revealed distortions in the electrode images. The fact is that the experimental conditions dictated the need to use large angles of field of view. As a result, distortions appeared in the electrode images. The distortion of the anode was weak because it was photographed directly, and the distortion of the cathode was stronger because not the entire cathode was photographed, only part of it. Figure 6 clearly shows multiple anode spots in the stage of spark discharge development. Figure 7 shows the stages of one spark (Figure 7a) and two (Figure 7b), as well as the transition from the spark stage to the arc, which is recorded for the first time (Figure 7c,d). The contact area with the anode spots is clearly visible (Figure 7a,b). A current channel is visible. Nearly every anode spot has a torch pointing towards the cathode. We can divide the spark discharges observed at the first stage of welding arc excitation into two types. The first kind of spark discharge happens when an arc discharge forms in the space between the cathode and anode. The current flow of charged particles in a conductive medium known as plasma causes this (Figure 4b-d). The second type of spark discharge manifests as an auxiliary spark discharge, taking place in a section far from the anode's surface, near the maximum value of 2-3 mm (refer to Figure 6b). Spark bindings and the formation of anode spots are visible on the periphery of the first spark discharge. We see a pronounced arc discharge column due to the strong, intense glow (Figure 7c,d). A column of plasma is clearly the brightest source of radiation, at least in the optical range of the spectrum. The column has grown, but at the same time, anode spots formed during spark discharge remain on the anode's surface. The cathode region has an intense glow, but already in Figure 7, individual cathode spots are visible, and new anode spots of arc discharge have formed on the surface of the anode in the cathode-anode gap. Simultaneously, the cathode spot (Figure 7d), located at the base of the cathode column, serves as the center of a diffusely luminous discharge region resembling a hemisphere. In the future, these anode spots will combine into one spot and cause strong heating and melting of the anode surface. The formation of a molten metal bath transforms the arc binding that pushes back through the anode spots into the diffusion form of discharge binding [50; 51]. It is well known [51] that current transfer to the cathodes of arc discharges in surrounding gases can occur both in the point mode, when most of the current is localized in cathode spots occupying a small part of the cathode surface, and in the diffuse mode. This mode distributes the electric current more or less evenly over the cathode's front surface. The diffuse mode is favored by a high average cathode surface temperature, which can be achieved by reducing the size of the cathode [51]. Many observations show that there are two main ways for the arc to burn at the anode: (a) with a counteracted (compressed) anode spot and (b) with a diffuse (spread out over a large surface) arc-anode contact zone.