DEUTERIUM TRAPPING IN GRAPHITES IRRADIATED WITH C+ IONS AT 350 AND 673 K

By means of NRA method the retention of D atoms was investigated in USB, RGT, PGI and POCO graphites after irradiation at 350 and 673 K with 200 keV C+ ions to different doses up to about 10 dpa followed by deuterium loading from D-2 gas at 1473 K under pressure of 0.66 Pa for 1 h. The aim was to understand the nature of deep traps for D atoms with E(D)(b) similar or equal to 4.5 eV, differences in deuterium accumulation in different graphites and the role of the irradiation temperature. After irradiation at 673 K the concentration, (C) over bar(D), of D atoms trapped in the ion stopping range in all the graphites except for USB is 1.5-2.0 times as low as in those after irradiation at 350 K and amounts to 600-800 appm. USB demonstrates a minimum gas retention (similar or equal to 100 appm), but it is more than that after implantation at 350 K. It was shown that deep traps are available in trace amounts in all graphites in their original state (about 10 appm) and can be created in the course of plastic deformation and/or fracture (up to about 100 appm). Deep traps are considered to be dangling bonds of C atoms along peripheral edges of interstitial clusters formed mainly due to radiation damage of graphites. Differences in the dose dependences of D retention, (C) over bar(D) ((K) over bar t), for different graphites irradiated at 350 and 673 K were discussed in frames of available knowledge on the damage buildup and relevant effects which greatly depend on the irradiation temperature.