24P054-P
Study of Hydrogen Isotopes Behavior in Graphite with PS-DIBA Device
PS-DIBAを用いた炭素中での水素同位体挙動に関する研究
Yuki Nakamura1, Masato Yamagiwa1, Noriaki Matsunami2, Noriyasu Ohno1,Makoto Takagi1, Shin Kajita2, Masayuki Tokitani3, and Suguru Masuzaki3
中村 祐貴, 山際 正人，松波 紀明，大野 哲靖，
高木 誠，梶田 信，時谷 政行，増崎 貴
1Graduate School of Engineering, Nagoya University, Fro-cho, Chikusa-ku, Nagoya, Aichi 464-8603, Japan
名古屋大学大学院工学研究科, 〒464-8603 名古屋市千種区不老町
2
EcoTopia Science Institute, Nagoya University, Fro-cho, Chikusa-ku, Nagoya, Aichi 464-8603, Japan
名古屋大学エコトピア科学研究所, 〒464-8603 名古屋市千種区不老町3National 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322-6

The measurement of dynamic behavior of hydrogen isotopes retention under plasma exposure is ofimportance for the hydrogen recycling in future fusion devices. We investigated deuterium behavior ingraphite using PS-DIBA(Plasma Surface Dynamics with Ion Beam Analysis) device. Nuclear Reaction
Analysis (NRA) in PS-DIBA was used to measure dynamic behavior of deuterium retention. The results
indicated that deuterium retention in graphite was almost constant during plasma exposure. And after theplasma was terminated, deuterium retention decreased by approximately 20%, which was thought tocorrespond to the dynamic retention.

1. Introduction
Carbon materials have been widely used as
plasma facing components and are the candidate
material for the vertical targets of the divertor platesof the ITER. However, carbon materials have adisadvantage of accumulating extremely highconcentration of hydrogen isotopes and radioactive
tritium in the case of D-T experiments. As the resultof longtime researches, hydrogen isotopes retention
characteristics such as temperature dependence anddepth profile in carbon materials have beeninvestigated. However, because of the difficulty ofthe measurement, hydrogen isotopes were measured
after plasma exposure termination except for a few
experiments. Thus, only a few experiments havemeasured so-called 'dynamic retention' observed
under plasma exposure until now [1,2]. Dynamic
retention is thought to affect major impacts onhydrogen recycling in future fusion devices. In thisstudy, we measured deuterium retention
characteristics on graphite under plasma exposure
with PS-DIBA (Plasma Surface Dynamics with Ion
Beam Analysis), a device which makes it possible
to carry out in-situ ion beam analysis of deuterium
retention under high density plasma exposure.
2. Experiments
A schematical experimental set-up is shown inFig. 1. This device is composed of a compact andpowerful DC plasma source using a LaB6 cathodeand a copper anode. D(3He,p)α nuclear reaction

analysis (NRA) using a Van de Graaff accelerator
was used to measure retained deuterium. A primaryenergy of a mass-separated 3He+ ion beam was 1.0
MeV. The retention was determined by integrating
the measured deuterium concentration over theentire detection depth. The fluence and flux of 3He+
were 5.6×1015 cm-2 and 3.1×1012 cm-2s-1,
respectively. The beam was collimated at thesample to a size of about 2×1 mm and the aquisition
time was 30 minutes. The sample was isotropic
graphite ETP-10 (IBIDEN CO., LTD) .

Fig.1 A schematic of the PS-DIBA device.

3. Results&Discussion
Figure 2 shows the time evolution of retained
deuterium measured with NRA in ETP-10. Initially,
from 0 to 30 minutes, the deuterium retention wasmeasured without plasma exposure. Then, plasma
was generated, and the deuterium retention wassaturated soon around the areal density of 6.5×1016
cm-2. The plasma parameters were fixed for 3 hours,
at the incident ion energy Ei and ion flux ΓD of 17eV and 6.8×1016 cm-2s-1 respectively. After theplasma termination, the deuterium retention ingraphite rapidly decreased by approximately 20 %,which was thought to correspond to the dynamicretention, and then slowly decreased with a decay
time (half life time) of 22 hours.

Fig.2 The time evolution of retained deuterium inisotropic graphite ETP-10 measured with NRA

4. Summary
Deuterium retention in isotropic graphite ETP-10
was measured. After producing the plasma,deuterium retention saturated around 6.5×1016 cm-2 ,and decreased by approximately 20 % just after
plasma termination. This decrease is thought tocorrespond to the dynamic retention, and thenslowly decreased with a decay time of 22 hours.
In Ref. [3], heavy dependence of deuterium
retention in graphite on sample temperature wasobserved. It indicates that deuterium retention ingraphite decreases with increasing temperature inthe range of < 1000 K.
Acknowledgement
This work is performed with the support andunder the auspices of the NIFS Collaboration
Researchprograms(NIFS08KOBP010,NIFS11KLEF003).
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Mater. 241-243 (1997) 1022-1025[2] G.M. Wright, D.G. Whyte, B. Lipschultz,R.P.Doerner, and J.G.Kulpin: J. Nucl. Mater.
363-365 (2007) 977-983[3] R.A. Causey and K.L. Wilson: J. Nucl. Mater. 138(1986) 57-64