The influence of nitrogen co-deposition in mixed layers on deuterium retention and thermal desorption

The influence of nitrogen co-deposition in ITER relevant mixed layers on retention and release dynamics of deuterium was studied in situ by Nuclear Reaction Analysis (NRA) and thermodesorption spectroscopy. W:Al and W:Be mixed layers deposited by thermionic vacuum arc (TVA) method were used in order to verify the possibility of Al being used as proxy material for Be in experiments regarding D uptake. Samples were exposed to neutral deuterium atom beam with fluence of 3.24 × 10¹⁹ D/cm² (flux 4.5 × 10¹⁴ D/cm²s) at 390 K and NRA with ³He ions was used for depth profile analysis of deuterium content after the exposure. For the investigation of deuterium release dynamics the samples were linearly heated to around 1000 K and during this process NRA spectra at single energy were collected every minute. Complementary to NRA a quadrupole mass spectrometer was used, following masses 2, 3 and 4 in the background vacuum. The numeric simulation of deuterium thermal desorption was performed and desorption energies of desorption sites were calculated. Same experiments were performed with mixed material samples produced by TVA in the presence of nitrogen atmosphere. Nitrogen co-deposition in the mixed layers was found to have an important influence on deuterium retention. The concentration of deuterium in the sample increased by a factor of 4.8 in the presence of nitrogen in the W:Al and by a factor of 1.8 in the W:Be layer compared to the nitrogen-free sample.