Carbon coatings for fusion applications

Abstract

The use of low atomic number material coatings in a fusion reactor plasma chamber may ease concern over maintaining plasma purity. A deposition process involving the discharge activated deposition of carbon coatings from methane at about 1 Pa pressure has been investigated. A coating of thickness 10 μm on copper has survived 1000 cycles of pulsed thermal heating at 37 MW m -2 with only minor flaking. The surface damage of similar coatings on stainless steel surfaces has been investigated for irradiation with 20, 40, 60 and 120 keV D + and He + ions at ambient temperature. Scanning electron microscopy of irradiated surfaces revealed no significant surface damage for either D + or He + irradiation with energies of 40 and 60 keV for doses of 4 × 10 22 and 8.1 × 10 22 ions m -2 respectively. For 120 keV D + and He + irradiations for a dose of 2.2 × 10 23 ions m -2, surface damage in the form of ridges was observed. A comparison of the results for carbon coatings with those obtained for ATJ graphite reveals that this type of graphite shows surface damage for all irradiations performed, while the carbon coating appears to be more resistant to damage for many of these irradiations. These results reflect favorably on the possible use of these coatings on various components in the plasma chamber of a fusion reactor.