Speaker
Katsunao Uenishi
(Osaka University)
Description
Sputtering properties of tungsten (W) should be evaluated correctly for lifetime estimation of divertor components. Especially, at elevated temperatures, recrystallization would cause grain structure reconstruction, which would influence sputtering properties and surface morphology changes. However, the detailed studies haven’t been performed.
Actually, the temperature of divertor could increase by slow transients to ~2,000 ˚C or more, which is higher than recrystallization temperature of W (~1,200 ˚C). In the previous study, the effect of recrystallization on sputtering was studied on iron (Fe). It was observed that grain orientation of Fe changes into that of small sputtering yield [1]. However, this effect hasn’t been investigated on W. In this study, the sputtering properties of W over recrystallization temperature is studied in detail. In addition, prior to the study of W, we have also investigated the sputtering properties and crystalline structure changes of Fe since Fe has the same bcc structure as W, which could give us important information on high temperature sputtering.
We performed deuterium (D) irradiation experiment to Fe. The irradiation energy and flux were 1 keV and ~102020 D/m22s. The sample temperature was varied between 473-973 K. The sputtering yield was estimated by mass loss measurements. After the irradiation, surface morphology were observed using a scanning electron microscope (SEM).
The sputtering yield of Fe by D irradiation is increased over ~720 K, which almost corresponds to the recrystallization temperature of Fe. The sputtering yield of 973K is about 1.4 times of 473 K. From observation of the surface morphology, surface roughness grew with increasing of temperature along with the sputtering yield and reached a few hundred nanometer in 973 K. We’ll also investigate the sputtering properties of W and compare with the results of Fe.
[1] Y. Ueda et al., J. Nucl. Mater. 386-391 (2007) 367-370
Co-authors
Heun Tae Lee
(Osaka University, Suita, Japan)
Katsunao Uenishi
(Osaka University, Suita, Japan)
Kenzo Ibano
(Osaka University, Suita, Japan)
Yosio Ueda
(Osaka University, Suita, Japan)
