黒鉛による水素同位体の捕獲と再放出 : 鉄不純物の影響及び再結合係数

概要

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To know the effect of metallic impurities deposited over the graphite first wall of thermonuclear fusion devices on the trapping-detrapping processes of fuel particles, the desorption processes of hydrogen isotope implanted into the graphite doped with iron (3at.%) was studied using XPS and TDS. Hydrogen isotope ions were implanted into a sample at room temperature with 5 keV using a conventional ion gun. An impurity modification phenomenon was found for the thermal desorption process. Namely, a new desorption peak (denoted as [Fe/C]-peak) appeared for the graphite doped with iron. The desorption mechanism for [Fe/C]-peak was explained by the second order surface recombination of trapped hydrogen atoms. The rate constants were determined as k(H2)=(7x10-4)exp(-59x103/RT) ; k(D2)=(4x10-4)exp(-59x103/RT) ; k(T2)=vd(T2)exp(-59x103/RT) ; where the frequency factor and activation energy are [1/molec・sec] and [cal/mol] unit, respectively. The recombination factor for hydrogen isotopes were estimated as kr(H2)=(1.5x10-15)exp(-59x103/RT)[cm4/molec・sec] ; kr(D2)=(9.6x10-15)exp(-59x103/RT) ; kr(T2)=vd(T2)x(2.6x10-12)exp(-59x103/RT) ; It was concluded that the impurity modification on the trapping-detrapping process is due to the increase in electronic charge on carbon caused by the presence of iron dopant.
富山大学の論文