Reseach Data--Simulation and experiment investigation of lamination W structure for suppressing surface blistering

In this study, it is considered that the use of tungsten(W) foils to form laminated W structures instead of W bulk can enhance the deuterium(D) plasma irradiation resistance of W plasma facing materials(W-PFMs). The gap between the W foils in the laminated W structure acts as a gas release channel to reduce the D retention in the W-PFMs, so that the D concentration in the W cannot reach the threshold and the blistering is suppressed. Based on this viewpoint, this study first performed finite element simulations and then D plasma irradiation experiments. Fig. 1 shows the geometric schematic of the simulation part of this study with the different boundaries and domains labeled, and the geometric dimensional parameters in Fig. 1 are given in Table 1. Fig. 2(a) is a schematic of the sample in the plasma irradiation experiment. Fig. 2(b) is a schematic of the electrolytic polishing of the sample. Fig. 2(c) shows the microwave electron cyclotron resonance (ECR) plasma irradiation device used in the irradiation experiment. Fig. 3 shows the temperature field results obtained from finite element simulation. Fig. 4 shows the results of the concentration distribution of mobile D atoms obtained by finite element simulation. The thermal parameters of the material, the diffusion coefficient of D atoms in the material and the solubility parameters of D atoms in the material are listed in Table 2. The parameters of the traps in the materials used in the finite element simulations are listed in Table 3. The parameters of the recombination coefficients for D for the materials used in the finite element simulations are listed in Table 4.Fig. 5 shows the D concentration distribution curves from the finite element simulation results. Fig. 5(a, b) show the D atom concentration versus depth curves along the W symmetry axis and at the interface between W and the gap, respectively. Fig. 5(c, d) show magnified plots of the concentration distributions in Fig. 5(a, b) in the near-surface region, respectively. Fig. 5(e) shows the variation with depth of the gas pressure of D gas in the gap along the symmetry axis boundary of the gap. Fig. 5(f) shows the variation of solubility of D atoms for different materials in the temperature range derived from Fig. 3. Fig. 6 shows the morphology of the sample surface before and after D plasma irradiation. Fig. 7 shows a cross-section of the bubbles in the W bulk and W foil using FIB. Fig. 8(a, b) show the statistical results for the blisters at different irradiation fluences. Fig. 8(c, d) shows the size and area fraction of surface blisters on W foils of different thicknesses after different fluences of irradiation. Both simulation and experimental results demonstrate that the thinner the W foil thickness, the more D retention and surface blistering are suppressed. This suggests that using W foils to form laminated structure instead of W bulk is effective in utilizing the gas release channel effect for suppressing surface blistering.