| Co-Investigator(Kenkyū-buntansha) |
ONO Futaba University of Tokyo, Faculty of Engineering, Research Associate, 工学部, 助手 (00011198)
YAMAGUCHI Kenji University of Tokyo, Faculty of Engineering, Associate Professor, 工学部, 助教授 (50210357)
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| Research Abstract |
Some transition metals exhibit "superpermeation" due to presence of surface impurity atomic layr with several monolayr thickness. The present project is aimed at demonstrating means to control surface impurity compositions for effective control of fuel particles in fusion devices, through examination of hydrogen-material interactions in the presence of surface impurities. To begin with, the experimental device was modified. As a result, irradiation of a mass-separated ion beam with sufficient flux density (>10^<17>m^<-2>s^<-1>) became possible in the energy range of 100 eV to several keV,together with simultaneous measurement of reemission (upstream-side) and permeation (downstream-side), due to an employment of differential pumpimg system. Using the experimental system described above, deuterium ion irradiation experiments were performed for Nb, Ti-6Al-4V and Mo. The results revealed that for Nb, which is known to exhibit superpermeation, the fraction of steady state permeation flux t
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o incident flux was 0.1, but when the downstream-side was irradiated by an Ar ion beam, significant increase of permeation flux was observed. For Ti alloy, which is known as low-activation material, similar permeation fraction (<approximately equal>0.2) was obtained. For these metals, the particle reflection coefficient, R_N, of incident deuterium was evaluated in the energy range of 150 to 1500eV/D,through post-irradiation thermal desorption spectroscopy. In the case of Mo, on the other hand, irradiation of Ar beam to the downstream-side surface did not change the permeation flux of deuterium, indicating that rate-determining step of permeation in Mo is different from that in Nb. The R_N of deuterium onto Mo was also evaluated and was compared with the result of computer simulation ; the experimental evaluation was smaller than the calculation result, whereas it was generally larger in the cases of Nb and Ti alloy. The effect of surface impurity on R_N is yet to be clarified, partly due to large experimental scatter. Less
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