Scale Symmetry of Stochastic Surface Clustering under Plasma Influence in Fusion Devices

Abstract

Titanium, tungsten, carbon, lithium, and beryllium surface structure were analyzed after plasma irradiation in fusion devices. Exceptional extreme high-temperature plasma load in fusion devices leads to specific surface clustering. It is strictly different from any other conditions of material’s clustering. The hierarchical granularity with cauliflower-like shape and surface self-similarity have been observed. Height’s distribution is deviated from the Gaussian function. The relief roughness differs qualitatively from the ordinary Brownian surface and from clustering under other conditions. In fusion devices, the specific conditions regulate material surface clustering faced to plasma. Ions and clusters melt on the surface and move under the effect of stochastic electromagnetic field driven by the near-wall turbulent plasma. In such a process, long-term correlations lead to the growth of surface with a self-similar structure. The multiscale synergistic effects influence the self-similarity–fractal growth from nanometers to millimeters. Experimental results illustrate universality of stochastic clustering of materials irradiated with plasma in fusion devices.