Investigation of Helium Ion Induced Damage in Nano-W Using UNU/ICPT Dense Plasma Focus Device

Abstract

Tungsten is the first choice for Plasma Facing Components because of their favorable properties such as high melting point, high threshold energy, low threshold shock resistance, resistance to form co-deposits with tritium. However, He irradiation defects on W may lead to Deuterium-Tritium reaction failure in the magnetic fusion reactors. In this work, we investigate the effects of helium ions flux, created by a UNU/ICPT dense plasma focus (DPF) device, on a PLANSEE double forged W and nanostructurized tungsten (nano-W). For the poly-W samples, SEM images showed the extent of surface and subsurface of W damage due to helium flux irradiation. The increase in numbers of hydrogen shots results in micro-cracks and blisters on the sample surface followed by re-solidification of the sputtered and melted surface. Nanostructurization of W has been achieved by exposing the W samples to Argon plasma in the UNU/ICPT DPF device to improve the performance. This results in well-distributed highly dense nanoparticles of ∼ 20–50 nm size. He ions exposed nano-W samples showed micro-cracks and nanopores, instead of blisters and holes. Back scattered imaging of the nano-W provides an indication of He bubbles trapping in the grain boundaries. The nano-W with improved surface and structural properties can be good candidate for plasma-facing materials.