Retention and desorption of implanted deuterium of high-Z plasma facing materials

Thermal desorption after D2+ irradiation from high-Z materials (W and Mo) has been compared with radiation induced microstructural evolution to investigate the details of retention and desorption of the implanted deuterium and underlying microscopic mechanism of the processes. The experimental results indicate that residual impurities act as major trapping sites for implanted deuterium independently of the ion energy for relatively low dose. The trapped deuterium is desorbed in two steps between 470 K and 660 K for high purity Mo, and 400 K and 650 K for high purity W. In the case of Mo damaged heavily at room temperature (1 x 1022 ions/m2), small cavities trap deuterium and give a large desorption stage at around 640 K. Radiation induced dislocation loops also trap the implanted deuterium effectively. (orig.)