Research On Erosion And Hydrogen Isotope Retention Of Marked Tungsten Samples In Tokamaks

Tungsten(W)is the most promising first-wall material because of its excellent material properties.During the operation of tokamak devices,the W impurity sputtered from the first-wall material will enter the scrape-off-layer(SOL)or even the core plasma,resulting in power loss even plasma disruption,which will affect the steady-state operation of tokamaks,or redeposit to the first-wall material surface,leading to the cycle of erosion-redeposition,affecting the material mechanical morphology and retention performance.In addition,hydrogen isotopes trapped in the wall material will affect the plasma density control and fuel efficiency.Besides,radioactive tritium will also affect the safety of the devices.In this paper,based on ion beam implanted depth marker technology,and using material and plasma evaluation system(MAPES)on China’s Experimental Advanced Superconducting Tokamak(EAST),and divertor probe on Korea Superconducting Tokamak Advanced Research(KSTAR)to perform W irradiation experiment.Through the international cooperation,taking a variety of characterization analysis to the marked tungsten after irradiation,to study the erosion and deposition behavior of rolling tungsten quantitatively,and the hydrogen isotopes retention behavior in tungsten.Firstly,the radiation properties of the tungsten material were studied on EAST.The impurity elements in Tokamak tend to deposited on the wire-electrode cutting surface,such as molybdenum,copper,carbon and other elements.With the extension of irradiation time,the total amount of deuterium retention increased,and the temperature of the first desorption peak was slightly higher than the irradiation substrate temperature,and a high temperature desorption peak of 1070K was found.After a short period of cumulative irradiation,the discrepancy of deuterium concentration in the tungsten surface of and sub-surface was slight,comparing with the former sample,the sample irradiated for longer time which deuterium concentration increased in the tungsten surface and decreased in sub-surface.Due to the limitation of the MAPES irradiation position,the surface morphology and erosion thickness changed mildly.This research could provide experience for the application of tungsten material in tokamaks.Secondly,material irradiation experiment was performed on KSTAR.Material surface cracked along the grain boundaries,compared to samples whose rolling direction perpendicular to the irradiation surface,the cracks on parallel samples were wider,and sputtered loss surface layer was thicker,various size of blisters appeared on different samples,and the pits due to blisters bursting were observed.Elements like carbon,iron,nickel,molybdenum,etc.from tokamak and sample holder were deposited on samples surface.Two high temperature desorption peaks with different content ratios were observed in all samples,the first peak was at 880K,and the second peak was at 1040K.Deuterium retention amount was greater in the sub-surface than the deeper solid.This study fully verified the viability of ion beam implanted marker technology in researching the erosion behavior of tungsten materials in tokamak environment,and provided experience and reference for the future research and analysis of tungsten materials in fusion devices.