Release of Hydrogen Isotopes from Boron Coated Carbon Tiles of JT-60U

Hydrogen isotope release properties of boron coated carbon tiles from JT-60U were investigated through secondary ion mass spectroscopy (SIMS). X-ray photoelectron spectroscopy (XPS) analysis of boron layer made by He+B₁₀D₁₄ method with 43 nm in thickness showed that the B/(B+C) ratio was about 0.9. Hydrogen isotopes in the boron layer and in the carbon layer were released at above 573 K and 1023 K, respectively. This means that hydrogen isotopes in the boron layer on the carbon tiles in JT-60U are released at temperatures as low as 573 K. The He+B₁₀D₁₄ boronization method is clearly effective to attain the high purity deuterium plasma and the low recycling because this method does not introduce H during boronization process. Wall conditioning before boronization is important because hydrogen retained in the carbon is released during plasma discharge through boron coating.