A. Sagara

K. Nishimura

M. Tokitani

N. Ashikawa

N. Matsunami

N. Ohno

S. Masuzaki

T. Sogawa

Y. Sakuma

National Institute for Fusion Science (NIFS-Repository)

  Oxide layers such as Fe2O3 will be formed on stainless steel (SUS), one of structure materials widely used for fusion devices [1], during removal process of hydrogen isotopes [2]. Thus, the depth distribution of deuterium (D) and amount of D-retention in the oxide layers are important for designing the devices. We have studied the depth profile of D and D-retention in Fe2O3 under low-energy D plasma exposure [3].   Fe2O3 layers were prepared by deposition of Fe on SiO2-glass substrates followed by oxidation in air at 400 to 500 ºC for more than 5 min. X-ray diffraction (XRD) shows that the oxide is α-Fe2O3, i.e., hematite (hexagonal corundum structure) and the composition is evaluated to be Fe:O=2:3 with an accuracy of 10% by Rutherford backscattering spectroscopy (RBS) of 1.8 MeV He+. RBS is also employed to evaluate the film thickness. Nuclear reaction, D(3He,α)P, analysis (NRA) with 1 MeV 3He+ was employed to obtain the depth profile of D. Here, the incident angle and detection angle of α-particles are 20º and 70º from the sample surface normal, respectively (NRA angle is 90º measured from the incident beam direction).     Figure 1 shows the depth profile of D in α-Fe2O3. One sees that D’s are distributed beyond the depth resolution (43 nm) and the range (30 nm) calculated [4] by considering the fractions of D3(60%), D2(38%) and D(2%) [5]. It also appears that more than 90 % of D’s are located within the film thickness of 0.1 μm, indicating small diffusivity of D in α-Fe2O3 near room temperature. By integrating the D density up to 0.2 μm, the amount of D-retention is obtained to be 45x1015 cm-2 and corrected to be 50x1015 cm-2 by taking 3He+ beam induced desorption (evaluated from measurement of D-retention vs 3He+ beam fluence) into account, in reasonable agreement with the reported value [3]. After the D-exposure, the XRD intensity decreased to 1/3 of that before D-exposure and the lattice parameter increased by 0.4 %. These modifications are not likely due to irradiation effects by low energy D (limited within 30 nm) but incorporation of D into Fe2O3 lattice.   In the mixed layers (more than 2 μm) of γ-Fe2O3 (maghemite, cubic spinel structure) and α-Fe2O3, which were prepared by oxidation of Fe at 400 to 500 ºC, the depth profile of D appears to be similar to that in α-Fe2O3, but D-density is larger than that in α-Fe2O3 in regions deeper than 0.1μm. D-retention is evaluated to be 73x1015 cm-2, by integrating the D-density up to 0.5 μm and correcting 3He+ beam induced desorption, the value being in agreement with the reported value (76x1015 cm-2 [3]). D-retention in the mixed layers is larger than that in α-Fe2O3. The difference could be largely due to the difference of the D-distribution mentioned above. D-retention in α-Fe2O3 is larger than that in Fe (12x1015 cm-2) and SUS316L (36x1015 cm-2). Measurements of D distribution in SUS and Fe, dynamic D-retention and thermal desorption of D are under way.     Fig. 1 Depth distribution of D density in α-Fe2O3 (thickness of 100 nm) normalized to Fe density exposed to D-plasma (1.5 kV AC glow-discharge in 0.5 Torr D2 for 30 min) (?). The dotted line indicates the range profile of D calculated using TRIM code [4].   1. C. Anandan, K.S. Rajam, Appl. Surf. Sci. 253 (2007)  6854. 2. R. E. H. Clark, D. H.  Reiter, eds. Nuclear Fusion   Research, Springer, 2004. 3. N. Matsunami, T. Sogawa, Y. Sakuma, N. Ohno,    M. Tokitani, S. Masuzaki, Phys. Scr. T415(2011)  014042, and D-retention in Fe2O3 is to be multiplied  by 2 for correction in NRA.  4. J.F. Ziegler, J.P. Biersack, U. Littmark, The Stopping   and Range of Ions in Solids, Pergamon Press, New   York, 1985. 5. H. Sugai, H. Kojima, T. Mori, S. Aoki, T. Okuda,  J. Nucl. Mater. 128/129(1984)169.  123§3. Depth Profile of Deuterium in Fe2O3 under Low-Energy Deuterium ExposureMatsunami, N., Sogawa, T., Sakuma, Y. (Nagoya Univ. EcoTopia), Ohno, N. (Nagoya Univ. Engineering), Masuzaki, S., Tokitani, M., Ashikawa, N., Sagara, A., Nishimura, K.

Depth Profile of Deuterium in Fe2O3 under Low-Energy Deuterium Exposure

Depth Profile of Deuterium in Fe2O3 under Low-Energy Deuterium Exposure

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