Studies of nanostructures formed in T-10 tokamak

Abstract

According to the X-ray diffraction (XRD) studies, hydrocarbon films and flakes formed under deuterium plasma discharges in T-10 tokamak are amorphous with graphene-like sheets. They have atomic ratio (D + H)/C about 1 and higher. The XRD peak positions revealed the presence of structural defects with interplane distances of 0.12, 0.24 and 0.66 nm. The peak widths gave the in-plane sizes of the scattering structures equal to about 1 nm. The properties of such films were studied with application of small-angle and wide-angle X-ray scattering measurements, neutron diffraction and other techniques. These experiments have shown that the films contain about 63% of sp3 and ∼37% of sp2 states. X-ray fluorescence spectroscopy employing synchrotron radiation revealed that the films contain at least 12 impurities of Fe, Mo, Cr, Ni, Nb and other transition metals. Difference between film properties on its opposite sides was revealed using Fourier-transform infrared spectroscopy and analysis of current-voltage characteristics (CVC). On the wall facing side of the film, graphite-like Csp2 structures dominate. On the plasma facing side, diamond-like Csp3 structures prevail. Deuterium retention can be monitored by two groups of vibrational sp3 modes with different oscillator strengths, depending on the amount of deuterium in films.