Comparison of deuterium retention in tungsten exposed to deuterium plasma and gas

•D retention in plasma exposure W is much higher than that of gas charging W.•D2 desorption temperature of plasma exposure W is lower than that of gas charging W.•Detrapping energy of D in gas charging W is 2.17 eV.•Detrapping energy of D in plasma exposure W is 1.04 eV. Deuterium (D) retention behavior in tungsten (W) exposed to D plasma and D2 gas was studied by means of thermal desorption spectroscopy (TDS): D plasma exposure in which W was exposed to D plasma with 35 eV/D+ at 393 K for 0.5 h to the fluence of 3.8 × 1024 D/m2; D2 gas charging in which W was exposed to D2 gas of 500 kPa at 773 K for 4 h. TDS shows that the total D retention in plasma exposure W is ~1022 D/m2, two orders of magnitude higher than that of gas charging W; however, the D2 desorption peak of gas charging W is 952 K, much higher than 691 K of plasma exposure W at the heating rate of 20 K/min. The detrapping energies of deuterium were determined experimentally from the measured peak temperatures at different heating rates and were found to be 2.17 eV for the gas charging W and 1.04 eV for the plasma exposure W, respectively.