Synergistic effects of high-heat loading, hydrogen and impurity deposition on surface modification of a tokamak limiter

The surface modification of a fixed molybdenum limiter used in TRIAM-1 was examined by means of SEM, EDS, and optical microscopy to identify the responsible modification mechanism. On the electron drift side, high-heat loading due to off-normal plasma operation and deposited impurities are the major factors which determine the mode of surface modifications. On the ion drift side local heat loading by arcing, hydrogen ion bombardment, and impurity deposition are the major surface modification processes.