Speaker
Takeru Maeji
(Osaka University)
Description
Currently, In regard to the plasma facing material, Tungsten (W) is a major candidate at ITER. A recent study has been reported indicating that the transient thermal load such as ELM or disruption causes metal surface melting or evaporation of W. However, the property and behavior of the W above the melting point has not yet been sufficiently known, and many of the previous studies are postmortem analyses. Thus in-situ observation of melting W is important.
In this study, a pyrometer measurement and a construction of two-dimentional (2D) temperature distribution measurement for the laser-melted W were performed to clarify the behavior of the W above the melting point. In the experiment, a Nd:YAG laser (1,064 nm, irradiation diameter 0.6 mm, maximum power 7 kW) has been used as a heat source that simulates a non-steady-state heat load, and the mirror-polished (surface roughness Ra 0.01μ) W samples (by A.L.T.M. Corp.) were irradiated. By measuring the temperature rise of the entire sample using a welded thermocouple, the energy absorption rate was measured. In order to obtain the energy absorption rate at a temperature above the melting point, time-varying laser irradiation pulses were applied. The surface temperature dependency of the energy absorption rate was then determined.
To investigate the W melt behavior in more detail, a 2D temperature measurement is being constructed. In the system, the black body radiation from the surface was delivered through half mirrors and band pass filters, to the sensor. The 2D temperature profile can be obtained by analysis of the two-color images.
Co-authors
Daisuke Inoue
(Osaka University, Osaka, Japan)
Eiji Hoashi
(Osaka University, Osaka, Japan)
Kazuyuki Mori
(Osaka University, Osaka, Japan)
Kenzo Ibano
(Osaka University, Osaka, Japan)
Kohei Yamanoi
(Osaka University, Osaka, Japan)
Nobuhiko Sarukura
(Osaka University, Osaka, Japan)
Satoru Yoshikawa
(Osaka University, Osaka, Japan)
Shinpei Kuroyanagi
(Osaka University, Osaka, Japan)
Takeru Maeji
(Osaka University, Osaka, Japan)
Yoshio Ueda
(Osaka University, Osaka, Japan)
