Hydrogen isotope diffusive transport parameters in pure polycrystalline tungsten

Hydrogen diffusive transport parameters in W coating for fusion applications

“…(4) the permeability of W layer is then obtained as P W,1 = 7.0 Â 10 À14 mol H 2 /m s Pa 0.5 and P W,2 = 4.9 Â 10 À13 mol H 2 /m s Pa 0.5 . These values are near the upper range [6] of a few published data at 400°C presented in Section 1.…”

“…For transport parameters in tungsten without traps the D L = 5 Â 10 À12 m 2 /s and S L = 9 Â 10 À4 mol H 2 /m 3 Pa 0.5 at 400°C were taken from the published data [2][3][4][5][6][7] that were measured on bulk tungsten. Since our S W ) S L it is obvious that majority of dissolved H atoms in our W layer are in traps and the total hydrogen concentration C tot.…”

“…Zakharov et al measured in the range 400-1200°C and obtained results give hydrogen solubility S = 7Á10 À5 mol H 2 /m 3 Pa 0.5 , hydrogen diffusivity D = 6 Â 10 À12 m 2 /s and hydrogen permeability P = DS = 4 Â 10 À16 mol H 2 /m s Pa 0.5 at 400°C [5]. Esteban et al [6] used time-dependent isovolumetric gas-phase desorption technique in the range 400-800°C with driving pressures from 1.3 Â 10 4 to 1 Â 10 5 Pa and obtained S = 9 Â 10 À4 mol H 2 /m 3 Pa 0.5 , D = 5 Â 10 À12 m 2 /s and P = 3 Â 10 À14 mol H 2 /m s Pa 0.5 . Franzen et al [7] studied the recycling properties of deuterium implanted in tungsten with a wide range of energies (100 eV, 1.5 keV, 8 keV) and sample temperatures (300-900 K) by modelling the results of reemission and thermal desorption (TDS) and subsequent isothermal desorption experiments.…”

Hydrogen gas driven permeation through tungsten deposition layer formed by hydrogen plasma sputtering

“…In Fig. 8, the estimated equilibrium concentration of hydrogen at 101,325 Pa of H 2 atmosphere is compared for W deposition layer and W bulk [5,6,10]. It was found that the equilibrium concentration of hydrogen in W deposition layer is enormously larger than that in W bulk.…”

“…The simulated pressure rise in the secondary volume by hydrogen permeation was fit to the experimental one by varying D and (S·P n ) as parameters. The obtained diffusivity was compared to the diffusivity in W bulk [5,6,10,11] in Fig. 7.…”