Influence of nitrogen pre-irradiation at different temperatures on surface blistering and deuterium retention in tungsten

Highlights: • The blistering on tungsten surface by deuterium implantation is suppressed by nitrogen pre-irradiation. • The deuterium retention in tungsten decreases largely due to the WN_xs layer. • Temperature has a signally influence on the nitrogen irradiation. - Abstract: Nitrogen seeding is considered to be used to reduce the power load onto tungsten divertor armors in tokamaks. Consequently, plasma-material interactions will be affected by seeded nitrogen impurities. The influence of nitrogen pre-irradiation on deuterium induced blistering and deuterium retention in rolled tungsten has been investigated at different pre-irradiation temperatures in the linear plasma device STEP with ion flux >10²¹ m⁻² s⁻¹. Commercially rolled W samples were sequentially exposed to nitrogen plasma (380 K and 470 K) and deuterium plasma (510 K). Surface observations show that nitrogen pre-irradiation suppresses deuterium-induced surface blistering. Thermal desorption spectroscopy measurements indicate that deuterium retention in the rolled tungsten is reduced due to nitrogen pre-irradiation, and it significantly changes with the pre-irradiation temperature. These phenomena are supposed to be related to the formation and change of WN_xs at different temperatures which is validated by X-ray photoelectron spectroscopy analyses.