Deuterium loading of redeposited-like W coatings present in tokamaks by ion implantation

Abstract

Pulsed Laser deposition (PLD) is a suitable technique to reproduce W, W–O and W–N–O coatings resembling those present in tokamaks walls, as protective W coatings covering plasma facing components (PFCs) or W-based layers redeposited in PFCs during reactor operation. Nevertheless, difficulties still exist to codeposit deuterium in all such layers, and parallel methods need to be implemented to load it. W-based coatings with porous and columnar microstructures grown by PLD where loaded with flat depth contents of deuterium down to 0.4–0.6 μm using multiple ion implantation steps at distinct incident energies and fluences. Deuterium amounts close to 7 at.% were easily achieved. Similar deuterium contents are commonly observed in deposits in now-a-days tokamaks. Microstructural characterization of the coatings was carried out by scanning electron microscopy (SEM). Quantitative elemental analysis of as-deposited and as-implanted materials was accessed by elastic backscattering spectroscopy (EBS), nuclear reaction analysis (NRA) and by time-of-flight elastic recoil detection (ToF-ERDA). Secondary ion mass spectrometry (SIMS) revealed the depth profiles of the existing isotopes and, particularly, of retained deuterium. Beyond their use in ex-situ experiments, the production is useful to calibrate laser induced breakdown spectroscopy (LIBS) and SIMS setups, aiming a standard free depth-quantification of deuterium in W-based coatings.