Radiation damage and impurity behavior in the superconducting tokamak TRIAM-1M under steady-state operation

Abstract

Abstract Radiation damage of plasma facing materials and the behavior of impurities in the scrape-off layer, under steady-state discharge of superconducting tokamak TRIAM-1M, was examined with using a rotatable collector probe. TEM observations of metallic probe specimens exposed to the discharges showed that numerous radiation induced defects such as dislocation loops and hydrogen clusters were formed. These are typical defects formed by low energy (< a few keV) hydrogen bombardment. Mo, Fe and Cr, which originated from Mo fixed limiters and the 304SS vacuum vessel walls, were deposited on the specimens. The deposition profile depended on the geometrical relationship with the main plasma and affected the internal damage of the specimens. It is worth noting that the density of the metallic impurities in the scrape-off layer was almost constant during the steady-state discharge and had no adverse effects on plasma confinement in the TRIAM-IM. Key Words: radiation damageplasma surface interactiontokamakhydrogen bombardmentinterstitial loops