Modification of the graphite tile surface in tokamaks

Abstract

The paper presents the results of experimental research on the surface modification of graphite protective elements from different graphite materials of MPG-8, RGT, ATJ, CFC, etc., types exposed in the T-10, T-11M, DIII-D, NSTX and Tore Supra tokamaks, as well as after plasma and ion irradiation in devices simulating wall boundary conditions in tokamaks. It is revealed that, in all cases of exposure, significant modification of the carbon-graphite materials surface occurs as a result of the plasma and ion beam. In addition, homogeneous pyrolitic layers with hexagonal planes oriented parallel to the irradiated surface are produced on the surface of protective elements. Thus, the physicomechanical characteristics of the plasma-facing surface degrade sharply. Application of a protective crystalline boron carbide coating reduces considerably the negative consequences of this phenomenon.