24P093-P
Structural analysis of carbon co-deposited layer in LHD
LHD における炭素再堆積層の構造に関する詳細解析
Naoko Ashikawa1), Kensuke Fukayama2), Yukinori Hamaji3), Yuji Yamauchi4), Yuji Nobuta5),
Kazunori Koga4), Masaharu Shiratani4), Yoshio Ueda3), Tomoaki Hino2), Takeo Muroga1)
and the LHD experimental group1)
1)

2)

3)

2)

2)

4)

4)

3)

芦川直子 ，深山健介 ，浜地志憲 ，山内祐二 ，信太祐二 ，古閑一憲 ，白谷正治 ，上田良夫 ，
2)
1)
1)
日野友明 ，室賀健夫 ，LHD 実験グループ
1)

National Institute for Fusion Science, 322-6, Oroshi-cho, Toki, Gifu 509-5292,Japan
核融合科学研究所 〒509-5292 岐阜県土岐市下石町 322-62)
Hokkaido University, Kita-13, Nishi-8, Kita-ku, Sapporo, Hokkaido 060-8628, Japan
北海道大学大学院工学研究院，〒060-8628 北海道札幌市北区北 13 条西 8 丁目3)
Osaka University, Yamadaoka, Suita, Osaka 565-0871, Japan
大阪大学工学研究科，〒565-0871 大阪府吹田市山田丘 2‑14)
Kyushu University, 744, Moto-oka, Nishi-ku, Fukuoka, Fukuoka, 819-0395, Japan
九州大学大学院システム情報科学府 〒819-0395 福岡県福岡市西区元岡 744

Graphitic structures of deposition layer on target samples have been applied Raman spectroscopy andX-ray photoelectron spectroscopy (XPS) in LHD. Those deposition layers show characterization ofamorphous carbon by Raman spectroscopy. The low amount of sp3 bonds are observed by XPS and the ratioof sp2 to sp3 by Raman is larger than that by XPS due to the difference of depth resolution.
1. Introduction
An estimation of retained hydrogen isotopes inplasma facing material is important issues in ITER
and Demo reactors. Carbon-based materials are still
one of the candidate and favorable for fusion
applications because of a low atomic number, goodthermo-mechanical properties, low coefficient ofthermal expansion and the absence of melting. Buthigh T retention in Carbon-based materials areserious problem due to safety maintenance after
vacuum vent, interaction between leaked water andcarbon dust in high vacuum level in vessel anddomestic regulation retained in vessel tritium inITER. In particular, carbon is known to takedifferent structures, such as graphite, amorphous,diamond, with different characterizations. On theother hand, the diamond like carbon (DLC) inindustrial investigations has been studied and a lotof groups are shown DLC characterization ofcarbon structure and hydrogen concentration using
different analytical methods. If characterizations ofco-depositied carbon can be shown correctly, arange of hydrogen isotopic retention will be
estimated by reference data in industrial
investigation.
In this study, using different type of carbon
deposition layer were made in LHD, there structural

analysis were investigated using Raman
spectroscopy and X-ray photoelectron spectroscopy(XPS).
2. Experiment
Target samples made by SUS316 and Si wereinstalled the section 6.5 at inner poloidal
cross-section in LHD. These samples were set in
the different facing holder and mainly two kinds ofgroup can be separated facing samples, namely S1and S2 and not facing samples, namely S3 and S4,
to graphite divertor targets. A different point of S1and S2 is the viewing angles from samples todivertor target.
Raman spectroscopy is sensitive to thegraphitic structures (phonon distribution) and has
been applied in order to study the structural changesof CBMs. Various CBMs, e.g. fine grain graphite,
pyrolytic graphite, diamond, CFC, glassy carbon,
were characterized.
XPS shows chemical bindings with depth
profile using Ar ion etching. Carbon 1s intensitiy
can be separated by fitting analysis and main
carbon peak was calibrated by experimental results
using Highly Oriented Pyrolytic Graphite (HOPG).
The top surface of HOPG was peeled off to reducesurface contaminations and lower surface layer wasAtomic concentration (%)

used the calibration analysis.
3. Results

G-peak (cm-1)

050
100

S2&S3

S1&S4

150
200

00.5

1Id/Ig1.5#S2100

BCOFeSi8060402000100200300

Depth (nm)4005002Fig.2. Atomic concentration of deposition layer onsample S2

Fig.1. Variation of Raman intensity ratios (ID/IG) oftarget samples vs. shifted G peak position of graphite by
Raman spectroscopy.

The Raman spectra from the target samples
exhibit two clear peaks, which correspond to thegraphite peak (G peak) around 1580 cm-1 and thedisordered peak (D-peak) around 1355 cm-1. Figure
1 shows the shifted G-peak position vs Raman
intensity ratios (ID/IG). All data shows the amorphouslike structure. Plotting data can be separated twogroups, one is the S2 & S3, and the other is the S1& S4. The situations of samples exposed to diverter
plasma and targets are separated S1 & S2 and S3 &S4, but the result in Fig.1 shows different
characterization.
Figure.2 shows the atomic concentration ofdeposition layer on target S2. Main composition iscarbon of 80% and a few amounts of O, Fe, B areobserved. As the sample data of carve fitting
analysis, chemical binding energy of carbon 1s isshown in Fig.3. Mainly three kinds of peaks, sp2,sp3 and CO of C1s were considered fitting analysis
and the sp2 satellite peak was negligible. From acomparison of Raman spectrum and XPS, the ratioof sp2 to sp3 is different. Because, the depth
resolution of XPS is sensitive as shown in Fig.2, but
Raman data shows integrated intensities indeposition layer of a few 100nm.
Quality of fitting analysis for C1s binding
energies is different on S1 and S2. Data on S2 atdifferent depth positions by XPS could be doneusing the same fitting parameters, but S1 could not
be done. The reasons are considered different
compositions and hydrogen concentrations [1] andthen carbon structure is also different. More details
will discuss in this poster.

Fig.3. Fitting analysis of carbon 1s at the depth of
31.8nm on sample S2.

Acknowledgments
This work was supported by the NIFS budget
UFFF028. The authors would like to thank Mr.
Nomura for support of Raman analysis.
References[1] K. Fukayama et al., this conference.