Graphite heat shield has a lower thermal conductivity relative to tungsten rod. This makes the temperature of graphite higher than tungsten (at same physical conditions) during Joule heating [19]. The contact of tungsten with heat shield at the contacting zone creates a cooler temperature field different from the usual temperature distribution field [20, 21] along the heat shield. Although the graphite heat shield is homogenous, tungsten has more influence on the part of heat shield closer to it within the temperature irregularity zone (broken circular yellow line in Fig.5.4). Hence the cooling effect of tungsten on the reference line within the temperature irregularity zone is the reason for lower temperatures at the stagnation point within the stagnation region in Fig.5.3.