It is well-known that plasma-material interaction (PMI) deeply modifies the plasma-facing components in the tokamak environment [1]. Due to their simplified geometry and magnetic field topology, PMI is usually investigated in linear plasma devices, using non-hydrogenic plasmas [2], such as Argon and Helium. These type of plasmas are of interest also in the tokamak environment. Indeed, Ar is considered as one of the most promising noble gas for radiative purposes, while the first phases of the ITER plasma discharges will be performed in He. Exposures in linear plasma devices usually involve the use of flat first-wall material samples, such as tungsten (W). However, it has been demonstrated [3] that a complex morphology, such as that characteristic of co/re-deposited layers in the tokamak environment, impact the angular distribution of sputtered particles, as well as reducing the sputtering yield. Modelling of experiments through dedicated codes, such as SOLPS-ITER [4] and ERO [5], might help in the interpretation of the experimental results. Recently, the ERO code has been upgraded to ERO2.0 [3] and applied also for the modelling of the morphology evolution at the micro/nano-scale. In this contribution, we therefore investigate, both numerically and experimentally, the modifications of W coatings with a complex morphology exposed to medium flux plasmas produced in the linear machine GyM (ne~1016 m-3, Te~7 eV, ?~5x1020 m-2 s-1, ?~7x1024 m-2) [6]. The selected plasma species is He, since its impact on materials modifications is of great relevance for the first phases of ITER. The plasma background needed ERO2.0 is obtained thanks to dedicated SOLPS-ITER simulations. Atomic Force Microscopy, Scanning Electron Microscopy and Weight Loss measurements are employed as the main characterisation techniques. AFM and SEM measurements are used in order to obtained a syntheticallygenerated W surface to be given as an input for the ERO2.0 code, which simulates its evolution due to the plasma irradiation. Simulation results are analysed in order to obtain a synthetically-generated SEM surface to be compared with experimental measurements, thereby helping in the validation of the morphology evolution module implemented in ERO2.0. The sputtering yield obtained by code simulations is compared with the experimental one, obtained from weight loss measurements. Coupled ERO2.0/SOLPS-ITER simulations are employed in order to understand the possible contribution of impurity in the sputtering of the exposed samples.
ERO2.0 and SOLPS-ITER modelling of rough W coatings exposures to He plasmas in the linear machine GyM
Uccello A;Dellasega D;Vassallo E;Pedroni M;Passoni M
2021
Abstract
It is well-known that plasma-material interaction (PMI) deeply modifies the plasma-facing components in the tokamak environment [1]. Due to their simplified geometry and magnetic field topology, PMI is usually investigated in linear plasma devices, using non-hydrogenic plasmas [2], such as Argon and Helium. These type of plasmas are of interest also in the tokamak environment. Indeed, Ar is considered as one of the most promising noble gas for radiative purposes, while the first phases of the ITER plasma discharges will be performed in He. Exposures in linear plasma devices usually involve the use of flat first-wall material samples, such as tungsten (W). However, it has been demonstrated [3] that a complex morphology, such as that characteristic of co/re-deposited layers in the tokamak environment, impact the angular distribution of sputtered particles, as well as reducing the sputtering yield. Modelling of experiments through dedicated codes, such as SOLPS-ITER [4] and ERO [5], might help in the interpretation of the experimental results. Recently, the ERO code has been upgraded to ERO2.0 [3] and applied also for the modelling of the morphology evolution at the micro/nano-scale. In this contribution, we therefore investigate, both numerically and experimentally, the modifications of W coatings with a complex morphology exposed to medium flux plasmas produced in the linear machine GyM (ne~1016 m-3, Te~7 eV, ?~5x1020 m-2 s-1, ?~7x1024 m-2) [6]. The selected plasma species is He, since its impact on materials modifications is of great relevance for the first phases of ITER. The plasma background needed ERO2.0 is obtained thanks to dedicated SOLPS-ITER simulations. Atomic Force Microscopy, Scanning Electron Microscopy and Weight Loss measurements are employed as the main characterisation techniques. AFM and SEM measurements are used in order to obtained a syntheticallygenerated W surface to be given as an input for the ERO2.0 code, which simulates its evolution due to the plasma irradiation. Simulation results are analysed in order to obtain a synthetically-generated SEM surface to be compared with experimental measurements, thereby helping in the validation of the morphology evolution module implemented in ERO2.0. The sputtering yield obtained by code simulations is compared with the experimental one, obtained from weight loss measurements. Coupled ERO2.0/SOLPS-ITER simulations are employed in order to understand the possible contribution of impurity in the sputtering of the exposed samples.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
