High energy density pulsed argon plasma synthesized nanostructured tungsten for damage mitigation under fusion relevant energetic he ion irradiation

Abstract

Tungsten (W) is considered as one of the promising candidates for plasma facing components in fusion reactors since it has high threshold energy, high melting point, low threshold shock resistance, and resistance against formation of co-deposits with tritium. Despite these commendable features, helium ions produced during fusion reaction are known to alter the microstructure of tungsten. In this work, dense plasma focus (DPF) device is used to study the effect of helium ion flux on double forged tungsten samples delivering a heat load of <math><mrow is="true"><mn is="true">6.27</mn><mspace width="0.33em" is="true"></mspace><mo linebreak="goodbreak" is="true">×</mo><msup is="true"><mn is="true">10</mn><mrow is="true"><mn is="true">4</mn><mspace width="0.33em" is="true"></mspace></mrow></msup><mrow is="true"><mi is="true">J</mi><mspace width="-0.16em" is="true"></mspace><mo linebreak="badbreak" is="true">/</mo><mspace width="-0.16em" is="true"></mspace><msup is="true"><mi is="true">m</mi><mn is="true">2</mn></msup></mrow></mrow></math> per shot. The irradiation of virgin W samples is carried out at 5, 10, and 15 DPF helium shots. High heat loads resulted in blisters and micro-cracks on the sample surface. With an increase in the number of shots, the density of the blisters increased and craters on the W surface burst followed by re-solidification of the melted and sputtered surface. Surface nano-structurization, with nanoparticle formation, of W samples (nano-W) is realized by high-energy argon ion exposure of virgin samples in an argon filled DPF device. The average size of nanoparticles is found to increase with the number of shots and also leads to particle agglomeration. At 10 shots, uniformly distributed highly dense nanoparticles of 20–50 nm size have been synthesized. The nano-W samples are then irradiated by instability-accelerated high-energy helium ions in helium filled DPF device for 5, 10, and 15 shots to simulate fusion relevant conditions. The presence of the trapped helium bubbles in virgin-W and nano-W are examined by BSE imaging and XRD, respectively. The nanostructured tungsten shows improved structure and surface properties against Helium ion irradiation.