SURFACE-ANALYSIS OF JT-60 GRAPHITE DIVERTOR TILES

The isotropic graphite ETP-10 was used as the divertor tiles (divertor plate) in the lower X-point configuration of JT-60. For these graphite tiles, numerous surface properties were investigated. The surface morphology was largely changed into a spongelike, column or smooth structure. The Raman spectroscopy analysis showed that the structure was composed of broadened crystal and defective structures, in addition to the amorphous structure, in every surface region. As the major impurities, O, Ti, Ni, Cr, and Fe were detected by both AES analysis and PIXE analysis. The total outgassing amount, measured by the technique of TDS, was one or two orders of magnitude larger than that of the as-received sample. At the surface within a depth of 50 nm, the hydrogen concentration ranged from 10 to 20 at%. A considerable amount of hydrogen was observed in the deeper region up to several millimeters.