In–out asymmetry of low-Z impurity deposition on the JT-60U divertor tiles

Abstract Low- Z impurity ( 7 Be) on the JT-60U divertor tiles was analyzed to study the impurity behavior in the divertor region. The amount of the 7 Be increased approximately one hundred times after B 4 C-tile installation in the outer divertor. The 7 Be was probably produced by 10 B(p,α) 7 Be nuclear reaction on the divertor tiles in the hydrogen experiment with ion cyclotron range of frequency heating. The 7 Be was distributed asymmetrically in the poloidal and the toroidal direction. The highest 7 Be concentration was found at the inner divertor whose boron content (B/(B+C) ∼ 20%) was lower than the B 4 C tiles (B/(B+C) ∼ 80%) of the outer divertor. This result may imply impurity transport from the outer divertor to the inner divertor.