# An Investigation into the Behavior of Cathode and Anode Spots in a Welding Discharge
## 3 Results
### Arc Discharge Stage
From the very beginning of combustion, the anode region presents a multitude of spots scattered over a relatively large area of the anode. Although individual spots are stationary, the entire group of spots can move along the anode's surface. In this case, as one moves, the old spots disappear and new ones appear. The mobility of the anode region increases depending on the atomic weight of the gas, a decrease in pressure, and an increase in the melting point of the anode material. The cathode spots on the surface of the tungsten cathode, depending on the current strength, and the welding discharge minus at the cathode and plus at the anode are shown in Figure 15. The number of spots on the cathode decreases as the current increases. However, the anode spots do not decrease at the same time. With such a large number of anode spots, the arc column bends due to their movement along the surface of the anode. The cathode spot also moves along the cathode's surface. Figure 16 shows cathode spots (KS) on the anode surface when the minus is on the anode and the plus is on the cathode. In Figure 16a,b, we see a round cathode spot of the second kind, with a plasma corona slowly moving along the surface. A powerful stream of vaporized matter and the emission of (thermo-auto) electrons are coming from the checkpoint. The plasma source in the gap is also droplets coming off the surface and generating plasma microclusters with plasma parameters close to the parameters of the  
Figure 8:0 Cathode spots on the surface of a tungsten cathode depending on the current strength, welding discharge minus at the cathode, plus at the anode: (**a**) current 8 A, (**b**) 10 A, (**c**) 15 A, (**d**) 18 A.  
spots--the so-called \"droplet spots\". In Figure 16b,c the anode spot formed on a tungsten cathode is shown for the first time. Studies have shown that KS of the second kind has a complex hierarchy [21; 26; 27]. On the same material, different researchers observed spots of different sizes passing different currents. This difference is due to the difference in arc burning modes (current and arc burning duration), as well as the spatial and temporal resolution available to one or another researcher. Consequently, the hierarchy of cathode bindings in a low-current vacuum arc is divided into distinct levels. For each level, a specific term is used to denote the observed spot and speak about its characteristic size, lifetime, current carried in the spot, and the level of voltage noise on the arc. Different authors use different terms. We will stick to the most common terminology here. The term \"macrospot\" is used to define objects of the highest level (in terms of size and transmitted current). The term \"spot\" is used for the middle level. The term \"cell\" refers to the lowest level with the smallest current and size. A \"macrospot\" type spot is an association of several \"spot\" type spots. The very spot of the \"spot\" type consists of a \"cell\". For copper, the characteristic dimensions of \"macrospot\" are (1-3) 10 2 cm, for \"Spot\" (1-2) 10 3 cm, and for \"Cell\" < 5.10 4 cm. In [27], it is also indicated that \"macrospot\" can also create associations called \"group spots\". Figure 8:1 Cathode spots on the surface of the anode when the minus is on the anode and the plus is on the cathode: (**a**) cathode spot on the surface of aluminum (reverse current polarity),there is no anode spot on tungsten (**b**) cathode spot on the surface of steel (reverse current polarity) coated with iron oxide, no anode spot on tungsten (**c**) cathode spot on the surface of steel (reverse current polarity) coated with iron oxide, a large anode spot on tungsten (**d**) a large spot on tungsten in the anode jet mode and a cathode spot on steel. Later, we conducted studies of the cathode spots left on the surface of the massive anode and film cathodes. Shown in Figure 17a,b are the autographs of the cathode spot on the massive anode. The spot exhibits an ellipsoidal shape and multiple, primarily circular, depressions.