27pB12
重水素プラズマ曝露したタングステンにおける表面化学状態変化と重水素滞留挙動
Study of correlation between deuterium retention behavior and surface chemical state
in deuterium plasma exposed tungsten
藤島徹生 1、小林真 1、川﨑淨貴 1、松山政夫 2 日野友明 3、山内有二 3、相良明男 4、信太祐二３、原正憲 2、田中政裕 4、芦川直子 4、大矢恭久 1、奥野健二 1
1
Tetsuo Fujishima , Makoto Kobayashi1, Kiyotaka Kawasaki1, Masao Matsuyama2, Tomoaki Hino3, et.al.
1

静大理放射研、2富山大水素研、3北大院工、4核融合研
Shizuoka Univ., 2University of Toyama, 3Hokkaido Univ.,4NIFS.

Tungsten will be used as a plasma facing material(PFM) in D-T fusion reactors. The PFM was exposed toD-T plasma and the hydrogen isotopes were implanted
into the PFM. In addition, a deposition layer wasformed by impurities like carbon and oxygen during
plasma operation, which led to cause higher hydrogenisotope retention in PFM. It is important to elucidate
fundamental tritium retention and transport behaviors intungsten under well-controlled condition forunderstanding fuel recycling in actual conditions. In
this study, the deuterium plasma exposure to tungstenof different grain boundary samples was performed toclarify the deuterium retention behavior and theformation of the deposition layer on the tungsten
surface during deuterium plasma operation at room
temperature as a preliminary experiment. The
deuterium retention for the plasma-exposed tungsten
was evaluated by TDS (Thermal Desorption
Spectroscopy), and the chemical states of the impurity
deposition layer were measured by XPS (X-ray
Photoelectron Spectroscopy).
Disk-type of stress-relieved polycrystalline tungsten(Stress-relieved),
recrystallized
polycrystalline
tungsten (Recrystallized) and single crystal tungsten(Single crystal), which were purchased from Allied
Material Co. Ltd., were used for all experiments. Thesamples size were 10 mm diameter and 0.5 mmthickness. The samples were preheated at 873 K for 30
minutes into the plasma exposure system to remove theimpurities. The D+ plasma exposure was carried out atroom temperature with the D+ ion energy of 100 eV.
The ion fluence was set to be (1.2-1.8) × 1025 D+ m-2.
After the plasma exposure, TDS measurements wereperformed from R.T. up to 1173 K with a heating rateof 0.5 K s-1 to investigate the deuterium desorption andretention behaviors. The chemical state and thethickness of the impurity deposition layer on thesamples were evaluated by XPS with using Ar+
sputtering technique.

The D2-TDS spectrum for Stress-relieved sample
consisted of two desorption stages at 400 K and 550 K.
The desorption stage at 400 K was attributed to thedesorption of deuterium adsorbed on the surface fromthe previous results. The deuterium retention as thedesorption stage at 550 K was increased with increasing
ion fluence. The irradiation defects would hardly
formed in tungsten sample during plasma exposure
according to SRIM (Stopping Range of Ion in Mater)
code calculation, it was considered that these deuterium
retentions were caused by the trapping of impurity
deposition layer and/or grain boundary. Figurecompares the D2-TDS spectra for Stress-relived,Recrystallized and Single crystal samples. The
deuterium retention of Recrystallized was 2.45 × 1019
D+ m-2, it was the largest among these samples. The
highest deuterium retention was derived for the Single
crystal sample. The Single crystal has no grainboundary, and the grain boundary of Recrystallized wasdifferent from the Stress-relieved. In addition, theimpurity deposition layers were formed, and thesechemical states and depth profile were the same witheach other. The impurity desorption layers wereconsisted of WO3 on the surface. This presentation
would be discussed about the effects of sample
chemical state and/or grain boundary on the deuterium
desorption behavior.
9.0

Desorption rate / 1016m-2 s-11Single crystal
Recrystallization
Stress-relived

8.0
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0.0

300

400500

600

700

800

900

Temperature / KFig D2 TDS spectra for W exposed todeuterium plasma