Effects of sequential helium and hydrogen ion irradiation on the nucleation and evolution of bubbles in tungsten

Irradiations of He+ and H+ have been performed to investigate the effect of H+ irradiation on existing helium bubbles and the effect of pre-irradiation of H+ on the formation of helium bubbles in tungsten. The specimens were irradiated at 800 °C with either 10kev-H+, 20kev-He+, or sequentially irradiated with both H+ and He+. After H+ irradiation, the growth of existing helium bubbles was observed. It was also found that pre- or post- irradiation of H+ enhanced the nucleation of helium bubbles. The growth of hydrogen bubbles was also observed after post irradiation of He+. The possible mechanism is discussed.