Helium retention of nickel

The helium ash causes fuel dilution and radiation loss, and makes the maintaining of self ignition condition difficult, therefore, it is required to limit the helium ash concentration in plasma to less than 10%. The exhaust of this helium is carried out with divertors, and in order to improve the exhaust efficiency, it has been investigated to install nickel and other metals near the divertors. In this research, helium ions and hydrogen ions were irradiated to nickel at different temperature, and the temperature dependence of the helium retention was examined. According to the results, the temperature range in which helium can be retained most was evaluated. Moreover, the effect that hydrogen ion irradiation exerted to the helium trap was examined. The samples, plasma irradiation and the measurement of the trapped quantity are explained. The trapping characteristics after the irradiation with helium only or hydrogen only, and the trapping characteristics of helium by the irradiation of helium-hydrogen mixture plasma are reported. (K.I.)