X-ray Photoelectron Spectroscopy Analysis of Changes in the Allotropic Structure of Samples of Tungsten and Carbon Subjected to Plasma Treatment

A signal processing technique for X-ray photoelectron spectroscopy has been developed, based on the interpretation of both the peak area and the energy loss region adjacent to the peaks of photoelectrons. The methodology is based on the method of partial intensities. The results of the calculation of partial coefficients obtained in the small-angle approximation are in good agreement with calculations performed using Monte Carlo simulation. It is noted that the calculation of partial coefficients, carried out in the smallangle approximation, allows for obtaining analytical expressions that significantly reduce computation time compared to the Monte Carlo simulation method, which is traditionally used for such calculations. This methodology has enabled the analysis of changes in the allotropic structure of materials subjected to helium plasma, simulating conditions at the plasma-wall interface in nuclear fusion devices. The changes in the allotrope type of MPG-8 grade graphite and tungsten under plasma exposure have been studied. It has been shown that the surface of the MPG-8 sample acquires a structure resembling pyrolytic graphite as a result of plasma exposure. It has been established that the dielectric permittivity of tungsten does not change when tungsten “fuzz” forms on the surface of the sample due to plasma action. There is a noted growth of tungsten carbide as a result of plasma exposure.