High-flux He+ irradiation effects on surface damages of tungsten under ITER relevant conditions

Abstract

A large-power inductively coupled plasma source was designed to perform the continuous helium ions (He +) irradiations of polycrystalline tungsten (W) under International Thermonuclear Experimental Reactor (ITER) relevant conditions. He + irradiations were performed at He + fluxes of 2.310 21-1.610 22 /m 2 s and He + energies of 12-220 eV. Surface damages and microstructures of irradiated W were observed by scanning electron microscopy. This study showed the growth of nano-fuzzes with their lengths of 1.3-2.0 m at He + energies of >70 eV or He + fluxes of >1.310 22 /m 2 s. Nanometer-sized defects or columnar microstructures were formed in W surface layer due to low-energy He + irradiations at an elevated temperature (>1300 K). The diffusion and coalescence of He atoms in W surface layers led to the growth and structures of nano-fuzzes. This study indicated that a reduction of He + energy below 12-30 eV may greatly decrease the surface damage of tungsten diverter in the fusion reactor.

W nano-fuzzes: A metastable state formed due to large-flux He+ irradiation at an elevated temperature

“…Polycrystalline W (Honglu, Xiamen) with a size of 1cm×1cm×2mm was used as the specimen. To generate the W nano-fuzzes, the polished W specimen was irradiated with low-energy (200eV) and large-flux (1.3×10 22 /m 2 ⋅s) He + plasmas in our LP-MIES system described previously [7,12]. The radio frequency power of 7.5kW was injected into the inductively coupled plasma (ICP) source, resulting in W surface temperature of 1480°C.…”

“…Kajita proposed that the formation and growth of W nano-fuzzes can be attributed to the diffusion and coalescence of He nano-bubbles at an elevated temperature [6]. Our previous study indicates that the diffusion and coalescence of He atoms in W surface layer can control the growth and structure of nano-fuzzes [7]. Coral-like or tree-like nano-fuzzes can be formed due to low-energy He + irradiation, depending on the energy and flux of He ions.…”

Detection and plasma assisted degradation of dye on reusable gold coated tungsten nanofuzz array surface-enhanced Raman scattering substrate

“…The irradiation parameters deployed in this study can be found in Table 1. More details regarding the equipment used can be found from our previous publications [26,27]. Two other typical dyes commonly used in the industry, namely X-BR and X-3B, were also characterized following the same procedures.…”

Microstructure evolutions of the W–TiC composite conducted by dual-effects from thermal shock and He-ion irradiation

“…Compared with commercial W, the surface of the W-TiC composite exhibits different damage behaviors after He-ion irradiation. Liu et al [27] found that the dense nano-fuzz was formed uniformly on the surface of W at the He-ion energy of > 70 eV or He-ion fluxes of > 1.3 × 10 22 He + m −2 s −1 . Al-Ajlony et al [28] found that the dense and tangled fuzz structure was formed on the surface of W with a high He-ion fluence of 9.2 × 10 24 He + m −2 .…”