On the Possibility of Surface Analysis by keV-Energy Proton Scattering in Magnetic Fusion Devices

Abstract

   Erosion and redeposition processes of plasma-facing materials in fusion devices are the essential factors affecting near-wall and core plasma parameters and device lifetime. To determine the possibility of in situ analyzing these processes we developed the experimental model of built-in surface analyzer utilizing low-energy proton scattering spectroscopy. We present the results of experimental approbation of the proposed method. The processes of erosion and redeposition of plasma-facing materials in fusion devices are some of the most important factors affecting the plasma parameters and the resource of the first wall. The method of analyzing thin layers on a surface using keV-energy proton scattering expands the functionality of determining the rate of erosion and deposition of layers with a large atomic number on a substrate from a light element, or, conversely, light layers on a heavy substrate, which is typical for modern fusion installations. The analysis of deposition and/or erosion consists in placing special marker targets with layers of material with a low atomic number and/or material with a large atomic number in the places of the installation in which it is supposed to study the rate of erosion and/or deposition, with the subsequent analysis of energy spectra of hydrogen ions reflected from exposed targets with energies in the kiloelectron-volt range. In this paper, estimates of the applicability of this technique directly in a fusion device are given, considering the characteristic parameters of the near-wall plasma.