Speaker
Daisuke Inoue
(Osaka University)
Description
Tungsten (W) is a primary candidate of plasma-facing materials for fusion reactors. But erosion due to melting and evaporation of W caused by transient heat loads are concerned. A pulsed laser simulating the transient heat loads was irradiated to three tungsten materials and the behavior of the molten layer was investigated. In addition, aluminum (Al) and tin (Sn) was deposited on W and the effects of the protective film was investigated.
Plate samples were installed in an ultrahigh vacuum and irradiated by Nd-YAG laser (wavelength 1,064 nm) onto the circular spot of a diameter of 0.6 mm. We prepared three W materials; pure W, W-10%Re and W-2%Ta. We observed samples after the heat loads irradiation with a laser microscope for surface profiling. In addition, thin films (1~3 μm) of Al and Sn were deposited on W samples using a magnetron sputtering device as protective films. Evolution of surface temperature was measured by a using two-color thermometer.
After irradiation in 2.33~3.68 GW/m2 2 to a pure W sample, the central part became dented, however, after irradiation in higher heat fluxes of 4.14~5.15 GW/m22, the central part protruded but not droplet ejection was observed. In contrast, the central part of irradiated W-2%Ta became dented deeply in wider range with increase in the power density, which could be attributed to the release of Ta droplets by bumping, closely related to microstructure and/or impurity concentration determined by the materials production processes. By using this laser melting technique, it is possible to evaluate molten layers behavior of W materials by giving laser heat loads and observing melting spots in detail.
Co-authors
Daisuke Inoue
(Osaka University, Suita city, Japan)
Kenzo Ibano
(Osaka University, Suita city, Japan)
Satoru Yoshikawa
(Osaka University, Suita city, Japan)
Takeru Maeji
(Osaka University, Suita city, Japan)
Yoshio Ueda
(Osaka University, Suita city, Japan)
