22D06
Hydrogen concentration of co-deposited films formed in Large Helical Device
大型ヘリカル装置における炭素-水素共堆積膜中の水素濃度
Kensuke Fukayamaa, NaokoAshikawab, Yuji Nobutac, Yuji Yamauchic, Tomoaki Hinoc, Suguru Masuzakib,
Kiyohiko Nishimurab,Akio Sagarab, LHD Experimental groupb
深山健介 a、芦川直子 b、信太祐二 c、山内有二 c、日野友明 c、増﨑貴 b、西村清彦 b、
相良明男 b、LHD 実験グループ baGraduate School of Engineering Hokkaido University

Kita-13, Nishi-8, Kita-ku, Sapporo, Hokkaido 060-8628, Japan
北海道大学大学院工学院 〒060-8628 北海道札幌市北区北 13 条西 8 丁目bNational Institute for Fusion Science322-6, Oroshi-cho, Toki, Gifu 509-5292,Japan
核融合科学研究所
c〒509-5292 岐阜県土岐市下石町 322-6

Faculty of Engineering 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

Hydrogen amount in co-deposit formed in fusion reactors depends on the structure of carbon.
So the deposition process, the relation of the co-deposits with the retention behavior andcharacteristics must be clarified to evaluate the reactor safety. In the present study, we installed
multifaceted holders with material probes on the wall near the graphite divertor in 13th
campaign of the LHD. We prepared different characteristic types of co-deposits, then thedeposition thickness, the retained amount, deposition amount, and hydrogen concentration of
the co-deposits were evaluated. The amount of retained hydrogen and deposited particles andthickness for the co-deposits which directly faced to the divertor were large. Hydrogenconcentrations in the co-deposits which did not face to the divertor became large.

1.Introduction
For the safety operation associated with thecharacteristic types of co-deposits, and then thedeposition

thickness,theretainedamount,limitation of in-vessel tritium inventory in fusion

deposition amount, and hydrogen concentration ofreactor, the retention behavior of hydrogen isotope

the co-deposits were evaluated.

and the characteristic of co-deposits must be
clarified, such as the relation of the depositing

2.Experiments

position with hydrogen retention and concentration.

To prepare the co-deposits with different incoming

In the present study, we prepared different

particles during the deposition, we installed amultifaceted sample holder in the LHD 13th

Amount of desorbed H2 and CH4 are shown inexperimental campaign as shown in Fig.1. The SS

Fig.2. The desorbed amounts, namely the amounts

and Si probes were fixed on the holder. S1 and S2of retained hydrogen, S1 and S2, which directly

directly faced the divertor plates. Opening angle offaced the divertor plates, were larger than that of S3

S2 was larger than that of S1. S3 and S4 did not faceand S4. The amount for S4 was less than thethe divertor plates.

detection

limit

of

our

measurement.

Fig.1.Diagram of multifaceted holders and thepositionFig.2. Amount of desorbed hydrogen
Duringtheexperiment,

probe

Most of deposition on S1 and S2 might be carbon

temperature and neutral particle pressures were theatoms resulted from sputtering on divetrot prates.

same. The amounts of retained hydrogen andCarbon atoms have high sticking coefficient, so it

deposited particles were evaluated by thermal

can easily form the co-deposit. Therefore, desorbed

desorption

amount of S1 and S2 became high.

spectroscopy

spectroscopy,

surroundingandrespectively.

Auger
Then,

electronhydrogenconcentrations of the co-deposit were evaluated.

The estimated hydrogen concentrations are shownin Fig .3.

3.Results and discussion
The deposited amounts of carbon, boron, and ironontheprobes

are

shown

in

Table

I.

Table I. Amount of deposition[1017atoms/cm2]

Fig.3. Hydrogen concentration
HydrogenFig.3.
concentration
S1 was extremely high.
Hydrogenofconcentration
The concentrations of S3 was little larger than that
The deposition amounts S2 were larger than S1.

of S2. For S2, the main incoming species might be

For S3 and S4, the deposition amounts were almost

carbon, so the hydrogen concentration became very

the same. Atomic concentration of carbon for S2

low. The higher concentration for S3 might be

was the highest among the probes.

owing to the deposition of hydrocarbon radicals.