24P081-P
Deuterium Behavior in Tungsten Coatings Irradiated with Mixed Ion Beam
混合イオンビームを照射したタングステンコーティング材料中の重水素挙動
Kazuhiro Uekita1, Oya Makoto1, Ohtsuka Yuusuke1, Ueda Yoshio1, Kasada Ryuta2,Kimura Akihiko2 and Nagasaka Takuya3
上北 一博1, 大宅 諒1, 大塚 裕介1, 上田 良夫1, 笠田 竜太2, 木村 晃彦2, 長坂 琢也3
1

Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan
大阪大学大学院工学研究科 〒565-0871 大阪府吹田市山田丘2-1
2Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan京都大学エネルギー理工学研究所 〒611-0011 京都府宇治市五ヶ庄
3National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292, Japan
核融合科学研究所 〒509-5292 岐阜県土岐市下石町322-6

W coatings on low activation materials such as ferritic steel (F82H), oxide dispersion strengthened (ODS)
steel, and vanadium alloy NIFS-HEAT2 (NH2) were exposed to low energy (1 keV) and high irradiation
flux (1020 D/m2s) of pure D ion beam and D/He mixed ion beam. The D retention properties of W
coatings were examined by thermal desorption spectroscopy (TDS). In addition, the surface modificationof W coatings was observed with scanning electron microscope (SEM). We discuss the influences ofsubstrate materials on the retention properties of W coating materials and the surface modification due toion beam irradiation.

1. Introduction
Tungsten (W) is a major candidate material
for the first wall in future fusion reactors
because of its high melting point and low
sputtering yield. However, W is generally
heavy in weight and has poor workability as W
is a high Z material [1]. One of the ways toovercome these disadvantages is to have W
coated on various low activation materials. Wcoatings on the substrates can be produced bymeans of vacuum plasma splay (VPS) process[2]. VPS process is useful for coating a large
area because of its relatively high coating rate.
At present, the study on the retention
properties of hydrogen isotopes (hydrogen,deuterium, and tritium) in the W coatings have
yet being carried out. Additionally, helium (He)produced in burning deuterium (D) and tritium(T) plasmas results in simultaneous irradiationof hydrogen isotopes and He to the first wall offusion reactors. In this study, we irradiate W
coatings on various materials with pure D ion
beam and D/He mixed ion beam. We
investigate the D retention properties of W
coatings and the surface modification afterirradiation.
2. Experimental
Four different W coating samples wereinvestigated. The first three samples were theW coating samples on F82H ferritic steel(F82H: Fe-8Cr-2W-0.1C), oxide dispersion
strengthened
ferriticsteel(ODS:Fe-19Cr-0.3Ti-0.3Y2O3)
andNIFS-HEAT2
vanadium alloy (NH2: V-4Cr-4Ti). The fourthsample was the pure W coating peeled from thesubstrate after coating on a bulk W. In
comparison with W coating samples, bulk W
sample was investigated with the same
experimental conditions. The dimensions of thesamples are as shown in Table I.
The irradiation experiment was performedby using the high flux ion beam test device(HiFIT), where the beam energy is 1 keV andthe irradiation flux is ~1 x 1020 D/m2s [3]. The
irradiation fluence was ~1 x 1024 D/m2. The
main experimental parameter varied was
sample temperature (473 K and 673 K). He
impurity was added to D ion beam byintroducing He gas into the plasma source,
where the He fraction in the flux was about 5%.
After the irradiation, the D retention
properties of the samples were analyzed withthermal desorption spectroscopy (TDS), wherethe samples were heated from RT to 1273 K
with a heating rate of 0.1 K/s. In addition, thesurfaces of the samples were observed withscanning electron microscope (SEM) to analyze
the surface modification due to ion beamirradiation.

3. Research plan
In this presentation, we show the D retention
properties of W coating materials on different
substrates and discuss how the substratematerials influence the D retention properties.
We characterize the front surface of different W
coatings to show the effect of ion beamirradiation
onW
coatingmaterials.
Furthermore, we discuss if the existence of He
in irradiation flux influences the properties of
W coating materials. Finally, we discuss
applicability of various W coating materials as
plasma facing materials in future fusion
reactors.
Table I. The dimensions of the samples (Thearea of the irradiation surface is 10 x 10 mm forall samples)
samplenumber
#1
#2
#3
#4#5

sampleF82H
substrate
ODS
substrate
NH2substratepeeled Wbulk W

totalsubstrateW
thickness thickness thickness
[mm]
[mm]
[mm]
1.5

0.9

0.6

1.5

0.7

0.8

1.5

0.7

0.8

0.8
1-0.8
1

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Muroga, Fusion Sci. Tech. 56(2009)1053.
[3] Y. Ueda, T. Shimada and M. Nishikawa, Nucl.
Fusion 44(2004)62.