Helium load on W-O coatings grown by pulsed laser deposition

TL;DR

This study investigates how helium implantation affects tungsten-oxide coatings grown by pulsed laser deposition, revealing differences in helium retention based on coating morphology, which is relevant for fusion reactor materials.

Contribution

It demonstrates a method to produce W-O-He coatings with controlled morphology using PLD and ion implantation, providing valuable reference samples for fusion research.

Findings

Porous coatings release helium faster over time.

Amorphous coatings retain helium at deeper layers.

Morphology influences helium retention and release behavior.

Abstract

W-O deposits with complex morphologies and significant He contents will growth on the surface of plasma facing components exposed to He discharges. To mimic the re/co-deposition process, W-O-He coatings were produced by implanting He+ ions on W films grown by pulsed laser deposition (PLD). The use of appropriate PLD experimental parameters such as Ar or He background atmospheres induces the deposition of porous or amorphous-like W-O structures, respectively. After multiple ion implantation stages using 150 keV, 100 keV and 50 keV incident He+ ion beams with a total fluence of 5 x 1017 ion/cm^2, significant amounts of He were identified in porous coatings by Rutherford backscattering (RBS). Time-of-flight elastic recoil detection (TOF-ERDA) measurements showed that most of the implanted He was already released from the porous coatings five month after implantation while for the case of amorphous ones the He content remains significant at deeper layers and smoothly decrease towards the surface, as result of a different morphology and nanostructure. The proposed method involving PLD and ion implantation seems adequate to produce W-O-He reference samples for fusion investigations.