Radiation damage of tungsten surface irradiated with high-energy hydrogen and helium beams of plasma focus device

Abstract

Tungsten (W) surface damages due to high-energy irradiations of a plasma focus device, including pure Hydrogen (H) ions, pure Helium (He) ions, and 50−50 H +He mixture was assessed. W is one of the candidate materials for use in the first-wall of nuclear fusion reactors such as tokamaks. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD) were utilized to analyze these damages. SEM images, in a good agreement with blister formation mechanisms proposed by large-scale atomic/molecular massively parallel simulator (LAMMPS) simulations, illustrated three different states. Due to the ability of He ions to increase the join probability of tiny blisters, the intermediate state of H+He mixture irradiation, including large individual blisters perches between two limit states of pure H and pure He irradiations, including tiny individual blisters and large clusters of blisters, respectively. AFM analyses confirm the role of He to provide the intermediate state based on values of roughness in these three states. XRD analyses show the considerable changes in the position and intensity of peaks. The shifted peak positions toward the higher angles present a mean value in the intermediate state of H+He mixture irradiation. Also, the medium peak intensity of the intermediate state clarifies the role of He in modulating the sharp behavior of H in the irradiation of W sample. The calculated compressive stresses show a moderate value for the irradiation with the H+He mixture.