Thermal annealing and exposure to divertor-like deuterium plasma of tailored tungsten oxide coatings

Abstract In this work we produced tungsten (W) and W oxide (WO<inf>x</inf>) films by pulsed laser deposition (PLD) with the aim of the addressing modifications of structure and morphology that occur after annealing treatments and high-flux deuterium plasma. Thanks to the high flexibility of PLD we produced nanostructured W containing non-bounded oxygen, different types of WO<inf>x</inf> and multilayered films. W coatings are dense, non-porous and exhibit a nanocrystalline structure, resembling the coatings used as first wall in tokamaks. The oxide films are nearly stoichiometric amorphous WO<inf>x</inf> (x = 3) with different morphology from compact to porous. Depending on annealing temperature, nucleation of different crystalline phases (e.g. WO<inf>3</inf>, W<inf>18</inf>O<inf>49</inf>) occurs. Exposure of films to high-flux (~10²⁴ m^-2 s^-1) deuterium plasmas in Magnum-PSI at different surface temperatures (T<inf>max</inf> = 580 K) determines material modifications at the nanoscale (e.g. nanometric defects) but no delamination. In addition preliminary deuterium retention results are reported.