Retention properties of plasma particles in tungsten exposed to LHD divertor plasmas

To study retention properties of plasma particles in tungsten exposed to divertor plasmas, material probe experiments were carried out by exposing tungsten specimens to long pulse helium or hydrogen divertor plasma in LHD. After the exposure, the quantitative analysis of the implanted helium and hydrogen atoms were conducted by using ion beam analytical techniques. Though the incidence energies were very low, remarkable retention of plasma particles were confirmed. In the case of helium divertor experiment, the specimen which located at the strike point (highest retention), the total retained helium atoms were estimated to be 1.2 × 1020 He/m2, and depth profile of helium atoms reached to about 25 nm. It is the much deeper range than that of the calculated results of 200 eV-He+ irradiation by TRIM-code. In the case of hydrogen, the total retention of hydrogen at the strike point was estimated to be 3 × 1019 H/m2 (lowest retention).