Radiation damage induced by plasma exposures under long duration tokamak discharge in TRIAM-1M

Prethinned specimens of Mo, Al and Cu were exposed to the boundary plasma under long pulse operation of the superconducting high-field tokamak TRIAM-1M to examine radiation effects of tokamak plasma on a microstructural change of plasma-facing materials. TEM observation of the specimens showed that interstitial-type dislocation loops and large elongated defects were formed, whose size and density depended on the position of the specimens. The former are considered to be formed by irradiations of energetic charge exchanged neutral hydrogen atoms. The latter are probably clusters of hydrogen atoms formed by strong bombardment of relatively low-energy hydrogen ions in the scrape-off layer. These defects are expected to have a strong influence on hydrogen recycling and degradation of plasma facing materials.