The Effect of Plasma Confined by Tokamak on Physical Properties of WO3 Nanostructures

To investigate the effect of plasma confined by Tokamak on the physical properties of tungsten oxide nanostructure (WO3), WO3 was deposited on stainless steel 316L (S.S.316L) via the Hot Filament Chemical Vapor Deposition (HFCVD) method in three filament temperatures (1600oC, 1750oC and 1900oC) and it was then installed on Tokamak chamber and exposed to 500 shots of hydrogen plasma. The forming and releasing of H2O also in addition to the ablated impurities from samples caused a significant decrease of plasma current and temperature and an increase of the H-alpha radiation. To investigate the effect of plasma shots on structural and morphological properties of deposited WO3, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were applied. Based on the XRD pattern and XPS spectrum, no observable changes in the position and intensity of XRD and XPS peaks before and after plasma shots were found. The comparison of SEM images of WO3/S.S.316L samples and S.S.316L show that the deposited sample in filament temperature 1600◦C (WO3/S.S.316L(1)) had the least morphology defect against plasma shots. Moreover, the AFM image of WO3/S.S.316L(1) shows the lowest level of evolution in surface roughness. On the other hand, the results indicate that the structural and morphological properties of the WO3 were dependent on the filament temperature as a result of the stability of WO3 against the plasma shots.